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Deleting from a relation

This operation deletes child objects from a parent in a relationship. The operation does not delete the actual objects, neither it deletes the relationship column. The operation simply disconnects the child objects from the parent.

Specific Children

There are multiple "flavors" of this operation, but in its core, it must reference a parent object and one or more child objects. The parent object must have a valid objectId value. The APIs are grouped below by how the parent object is identified - using objectId, as a map, as an instance of a custom class or as a result of a previous operation in the same transaction:

// Break the relation between the objects identified with objectId values in the 
// childrenObjectId array and the parent object identified with parentObjectId. 
// The parent object must be in the table with the parentTableName name. 
// The relationship column between the parent and child objects is columnName. 
// In other words, disconnect the child objects from the parent object for the
// relationship identified by columnName. 
unitOfWork.deleteRelation( tableName: string, 
                           parentObjectId: string, 
                           columnName: string, 
                           childrenObjectId: string[] );

// Same as the above with the only difference is the child objects are instances
// of a developer-defind custom class. It is important that 
// the class of objects in the children array matches the child table name. 
// For example, if the relationship is between tables Person and Address, then the 
// class of child objects must be "Address". Every child object must have the
// "objectId" key with a valid value.
unitOfWork.deleteRelation( tableName: string, 
                           parentObject: object, 
                           columnName: string, 
                           children: object[] );

// Break the relation between the objects represented by the "children" argument
// and the parent object. The parent object is identified by its objectId with the 
// parentObjectId argument. The parent object must be stored in a table with the
// parentTableName name. The "children" argument is a result of a previous operation
// in the same transaction. It must represent either a collection of string values
// (objectIds) or a collection of objects. This is possible with the following 
// previous operations:
//   - Retrieving objects from the database
//   - Saving multiple objects in the database
// It is important that all child objects referenced by the children argument exist
// in the child table that columnName points to.
unitOfWork.deleteRelation( tableName: string, 
                           parentObjectId: string, 
                           columnName: string, 
                           children: OpResult[] );
// Break the relationship between the objects from the childrenObjectId array 
// and the parentObject. The array must contain objectId values of the child 
// objects. The parent object must be in the table with the parentTableName 
// name. The relationship column between the parent and child objects is 
// columnName. In other words, for the relationship represented through the 
// columnName column, disconnect the child objects from the parent object. 
// The parent object is a map of key/value pairs. One of the pairs must be 
// objectId with the corresponding value. The children are identified with 
// their objectId values.
unitOfWork.deleteRelation( tableName: string, 
                           parentObject: object, 
                           columnName: string, 
                           childrenObjectId: string[] );

// Same as the above with the only difference is the child objects are instances
// of a developer-defined class. It is important that the class of child objects
// matches the child table name. For example, if the relationship is between 
// tables Person and Address, then the child objects class must be "Address".
// Every child object must have the "objectId" field with a valid value.
unitOfWork.deleteRelation( tableName: string, 
                           parentObject: object, 
                           columnName: string, 
                           children: object[] );

// Break the relationship between the objects represented by the "children" 
// argument and the parent object. The parent object must have the "objectId" 
// key with a valid value. Additionally, the parent object must be stored 
// in a table with the parentTableName name. The "children" argument is a 
// result of a previous operation in the same transaction. It must represent 
// either a collection of string values (objectIds) or a collection of objects. 
// This is possible with the following previous operations:
//   - Retrieving objects from the database
//   - Saving multiple objects in the database
// It is important that all child objects referenced by the children argument 
// exist in the child table that columnName points to.
unitOfWork.deleteRelation( tableName: string, 
                           parentObject: object, 
                           columnName: string,  
                           children: OpResult[] );
// Disconnect the objects identified with objectId values in the 
// childrenObjectId array from parentObject for a relationship column 
// with the name of columnName. The parentObject class must have the 
// "objectId" key wiith a valid value. The child objects are identified
// with their objectId values. It is important that the class of 
// parentObject matches the parent table name. For example, if parentObject
// class is "Person", it means Backendless wiil:
// 1. Look for the parent object in the Person table
// 2. Locate a column with the columnName name in the Person table
// 3. Using the column definition, Backendless will identify the child table
// 4. Backendless will retrieve the child objects from the child table using 
//    the provided objectId values.
// 5. Backendless wiill disconnect the child objects fom the relationship 
//    with the the parent object.
unitOfWork.deleteRelation( parentObject: object, 
                           columnName: string, 
                           childrenObjectId: string[] );

// Same as the above with the only differennce is the child objects are 
// instances of a developer-defined class. It is important that 
// the class of child objects matches the child table name. For example, 
// if the relationship is between tables Person and Address, then the 
// child objects class must be "Address". Both parentObject and children
// must have the "objectId" key with a valid value.
unitOfWork.deleteRelation( parentObject: object, 
                           columnName: string, 
                           children: object[] );

// Same as the first signature above with the only difference is the children
// argument is a result of a previous operation in the same transaction. It 
// must represent either a collection of string values (objectIds) or a 
// collection of objects. This is possible with the following previous 
// operations:
//   - Retrieving objects from the database
//   - Saving multiple objects in the database
// It is important that all child objects referenced by the children argument 
// exist in the child table that columnName points to.
unitOfWork.deleteRelation( parentObject: object, 
                           columnName: string, 
                           children: OpResult );
// Disconnect the children identified with their objectId values in the 
// childrenObjectId array from parentObject for the relationship identified
// by the column with the name of columnName. The parentObject value is a 
// result of a previous operation in the same transaction. These 
// operations can be:
//   - Saving a single object in the database
//   - Updating a single object in the database
// The relationship column must be declared in the same table where 
// parentObject comes from. It is important that all child objects in the 
// childrenObjectId array exist in the child table that columnName points to.
unitOfWork.deleteRelation( parentObject: OpResult, 
                           columnName: string, 
                           childrenObjectId: string[] );

// Same as the above with the difference that the child objects are instances 
// of a developer-defined class. The class used for child objects 
// must match the name of the child table. Suppose the relationship is 
// between tables Person and Address. In this case, the name of the child 
// objects class must be Address. It is important that each child object
// has the "objectId" key with a valid value.
unitOfWork.deleteRelation( parentObject: OpResult, 
                           columnName: string, 
                           children: object[] );

// Same as the first signature above with the only difference is the child 
// objects are untyped, plain JS objects. It is important that each child object 
// has the "objectId" key with a valid value.
unitOfWork.deleteRelation( parentObject: OpResult, 
                           columnName: string, 
                           children: object[] );

// In this operation both the parent and the children objects are results of 
// two separate previous operations in the same transaction. The parent 
// object must be a result of any of the following operations:
//   - Saving a single object in the database
//   - Updating a single object in the database
// The relationship is identified through the column with the name in the 
// columnName argument. The column must be declared in the same table where 
// parentObject comes from. The children argument can be a result of the 
// following operations:
//   - Retrieving objects from the database
//   - Saving multiple objects in the database
// It is important that all child objects referenced by the children argument 
// exist in the child table that columnName points to.
unitOfWork.deleteRelation( parentObject: OpResult, 
                           columnName: string, 
                           children: OpResult );

// This method and the ones listed below identify the parent object the 
// same way - using the OpResultValueReference class. This is a special 
// class which references an object within a result of annother operation 
// withhin the same transaction. For example, a result of another operation 
// can be a collection of objects. That collection can be returned from 
// either the "Retrieving objects" or "Saving multiple objetcs" operations. 
// All transaction operations return an OpResult object. Using the OpResult 
// API you can obtain a single object which can be used as parent in the 
// operations listed below. When a single object from a collection represented 
// by OpResult is referenced, it is represented by the OpResultValueReference 
// class.
unitOfWork.deleteRelation( parentObject: OpResultValueReference, 
                           columnName: string, 
                           objectIds: string[] );

unitOfWork.deleteRelation( parentObject: OpResultValueReference, 
                           columnName: string, 
                           children: object[] );

unitOfWork.deleteRelation( parentObject: OpResultValueReference, 
                           columnName: string, 
                           children: OpResult );

Children with a Query

There are APIs where the child objects can be identified with a query using a where clause. These APIs run a query to get the child objects and then disconnect them from the parent in the relation. Again the APIs are grouped by how the parent object is identified:

// Disconnect the child objects identified by whereClauseForChildren from 
// the parent object identified with parentObjectId. The parent object must
// be in the table with the parentTableName name. The relationship column 
// between the parent and child objects is columnName. The whereClauseForChildren
// query is executed in the child table that columnName points to.
unitOfWork.deleteRelation( tableName: string, 
                           parentObjectId: string, 
                           columnName: string, 
                           whereClauseForChildren: string );
// Disconnect/remove the objects identified by whereClauseForChildren from 
// the parent object represented by the parentObject map for a relationship 
// identified by column columnName. The parent object must be in the table 
// with the parentTableName name. It is important that parentObject has the
// "objectId" key with a valid value. The whereClauseForChildren query is 
// executed in the child table that the columnName column points to. 
// Objects which match the whereClauseForChildren query are then disconnected 
// from the parent object.
unitOfWork.deleteRelation( tableName: string, 
                           parentObject: object, 
                           columnName: string, 
                           whereClauseForChildren: string  );
// Disconnect the objects identified by whereClauseForChildren from 
// the parent object. The parent object is an instance of a 
// developer-defined custom class. The relationship column between 
// the parent and child objects is columnName. The data table where 
// the parent object is stored must match the name of the parentObject 
// class. For example, if the parentObject class is "Person", it 
// means Backendless wiil:
// 1. Look for the parent object in the Person table.
// 2. Locate a column with the columnName name in the Person table.
// 3. Using the column definition, Backendless will identify the 
//    child table.
// 4. Backendless will run the whereClauseForChildren query in the 
//    child table to identify the child objects.
// 5. Backendless wiil disconnect the child objects from the parent object 
//    for the relationship.
// The parentObject must have the "objectId" key with a valid value.
unitOfWork.deleteRelation( parentObject: object, 
                           columnName: string, 
                           whereClauseForChildren: string  );
// Disconnect/remove the objects identified by the 
// whereClauseForChildren query from the parent object. 
// The parentObject value is a result of a previous 
// operation in the same transaction. These operations 
// can be:
//   - Saving a single object in the database
//   - Updating a single object in the database
// The relationship is identified through the column with
// the name in the columnName argument. The column must be
// declared in the same table where parentObject comes from. 
// For example, if the parent object is stored in a table 
// called "Person", Backendless wiil:
// 1. Look for the parent object in the Person table
// 2. Locate a column with the columnName name in the Person 
//    table
// 3. Using the column definition, Backendless will identify 
//    the child table
// 4. Backendless will run the whereClauseForChildren query 
//    in the child table to identify the child objects
// 5. Backendless wiil disconnect the child objects from the
//    parent object for the relationship.
unitOfWork.deleteRelation( parentObject: OpResult, 
                           columnName: string, 
                           whereClauseForChildren: string );

// Same as the above except the parentobject is a reference 
// to an object  within a result of annother operation in the same
// transaction. For example, a result of another operation can be
// a collection of objects. That collection can be returning from
// either the "Retrieving objects" or "Saving multiple objetcs"
// operations. Using the OpResult API you can obtain a single 
// object which can be used as parent in this operation. When 
// a single object from a collection represented by OpResult is
// referenced, it is represented  by the OpResultValueReference class.
unitOfWork.deleteRelation( parentObject: OpResultValueReference, 
                           columnName: string, 
                           whereClauseForChildren: string );

Return Value

The operation returns an OpResult object which represents the result of this operation - number of child objects disconnected from the parent in  the relation.

Examples

The examples are organized by two levels: first is how the parent object is represented in the client program, then by the type of the child collection.

Parent object is represented as

The child objects are represented as

const unitOfWork = new Backendless.UnitOfWork();

// This is an array for child objects.
// They are referenced using objectId values.
// The example hard-codes the array, but in
// your code you'd get the objectId values
// from your data model or using a query
const giftIds = [ 
   "EE3BF4B5-DB88-1425-FF89-CC11B7707500",
   "0CF23E36-FCC0-4E04-FF3E-8B67E6E27200",
   "DFFEDE1D-E423-2472-FF71-26EEC3F23700" 
]

// this is the objectId of the parent object.
const personObjectId = "E7AD83E0-1B4E-D250-FF46-61BFAB18D700";

// the name of the table where the parent object is stored
const parentTableName = "Person";

// the name of the relation column
const relationColumnName = "wishlist";

// add the deleteRelation call to the transaction
unitOfWork.deleteRelation( parentTableName,
                           personObjectId,
                           relationColumnName,
                           giftIds );

// run the transaction
unitOfWork.execute()
   .then(function (unitOfWorkResult) {
       // transaction is complete. Use uowResult to check the result
   })
   .catch( function( error ) {
       // Server reported an error.
   });

const unitOfWork = new Backendless.UnitOfWork();

// This is a list of gift objects. These objects
// will be children in the relationship. As you
// can see the objects are constructed manually
// and their objectId's are set, however, in your
// application they would be loaded from the
// server. This is done here to keep the example
// more succinct.
const gifts = [
   {objectId : "EE3BF4B5-DB88-1425-FF89-CC11B7707500"},
   {objectId : "0CF23E36-FCC0-4E04-FF3E-8B67E6E27200"}
]

// the name of the table where the parent object is stored
const parentTableName = "Person";

// the name of the relation column
const relationColumnName = "wishlist";

// add the deleteRelation call to the transaction
unitOfWork.deleteRelation( parentTableName,
                           personObjectId,
                           relationColumnName,
                           gifts );

// run the transaction
unitOfWork.execute()
   .then(function (unitOfWorkResult) {
       // transaction is complete. Use uowResult to check the result
   })
   .catch( function( error ) {
       // Server reported an error.
   });

const unitOfWork = new Backendless.UnitOfWork();

// This is an array for child objects.
// They are referenced using objectId values.
// The example hard-codes the array, but in
// your code you'd get the objectId values
// from your data model or using a query
const gifts = [
   new Gift({"objectId" : "EE3BF4B5-DB88-1425-FF89-CC11B7707500"}),
   new Gift({"objectId" : "0CF23E36-FCC0-4E04-FF3E-8B67E6E27200"})
]

// this is the objectId of the parent object.
const personObjectId = "E7AD83E0-1B4E-D250-FF46-61BFAB18D700";


// the name of the table where the parent object is stored
const parentTableName = "Person";

// the name of the relation column
const relationColumnName = "wishlist";

// add the deleteRelation call to the transaction
unitOfWork.deleteRelation( parentTableName,
                           personObjectId,
                           relationColumnName,
                           gifts );

// run the transaction
unitOfWork.execute()
   .then(function (unitOfWorkResult) {
       // transaction is complete. Use uowResult to check the result
   })
   .catch( function( error ) {
       // Server reported an error.
   });
The Gift class is shown below:
function Gift(args) {
    args = args || {};
    this.objectId = args.objectId || "";
    this.name = args.name || "";
    this.price = args.price || "";
}

const unitOfWork = new Backendless.UnitOfWork();

// compose a query to fetch the gift objects
const queryBuilder = Backendless.DataQueryBuilder.create();
queryBuilder.setWhereClause("name in ( 'Apple iPad', 'Apple iPhone', 'Selfie Stick')" );

// add the find operation to the transaction
// notice the result of the operation is saved in a constant -
// it will be used further in the setRelation operation
const gifts = unitOfWork.find("Gift", queryBuilder);

// this is the objectId of the parent object.
const personObjectId = "E7AD83E0-1B4E-D250-FF46-61BFAB18D700";

// the name of the table where the parent object is stored
const parentTableName = "Person";

// the name of the relation column
const relationColumnName = "wishlist";

// add the deleteRelation call to the transaction
unitOfWork.deleteRelation( parentTableName,
                           personObjectId,
                           relationColumnName,
                           gifts );

// run the transaction
unitOfWork.execute()
   .then(function (unitOfWorkResult) {
       // transaction is complete. Use uowResult to check the result
   })
   .catch( function( error ) {
       // Server reported an error.
   });

The child objects are represented as

const unitOfWork = new Backendless.UnitOfWork();

// This is an array for child objects.
// They are referenced using objectId values.
// The example hard-codes the array, but in
// your code you'd get the objectId values
// from your data model or using a query
const giftIds = [ 
  "EE3BF4B5-DB88-1425-FF89-CC11B7707500",
  "0CF23E36-FCC0-4E04-FF3E-8B67E6E27200",
  "DFFEDE1D-E423-2472-FF71-26EEC3F23700" 
]

// this is the objectId of the parent object.
const personObjectId = {"objectId" : "E7AD83E0-1B4E-D250-FF46-61BFAB18D700"}


// the name of the table where the parent object is stored
const parentTableName = "Person";

// the name of the relation column
const relationColumnName = "wishlist";

// add the deleteRelation call to the transaction
unitOfWork.deleteRelation( parentTableName,
                           personObjectId,
                           relationColumnName,
                           giftIds );

// run the transaction
unitOfWork.execute()
   .then(function (unitOfWorkResult) {
       // transaction is complete. Use uowResult to check the result
   })
   .catch( function( error ) {
       // Server reported an error.
   });

const unitOfWork = new Backendless.UnitOfWork();

// This is a list of gift objects. These objects
// will be children in the relationship. As you
// can see the objects are constructed manually
// and their objectId's are set, however, in your
// application they would be loaded from the
// server. This is done here to keep the example
// more succinct.
const gifts = [
   {"objectId" : "EE3BF4B5-DB88-1425-FF89-CC11B7707500"},
   {"objectId" : "0CF23E36-FCC0-4E04-FF3E-8B67E6E27200"}
]

// this is the objectId of the parent object.
const personObjectId = {"objectId" : "E7AD83E0-1B4E-D250-FF46-61BFAB18D700"}


// the name of the table where the parent object is stored
const parentTableName = "Person";

// the name of the relation column
const relationColumnName = "wishlist";

// add the deleteRelation call to the transaction
unitOfWork.deleteRelation( parentTableName,
                          personObjectId,
                          relationColumnName,
                          gifts );

// run the transaction
unitOfWork.execute()
   .then(function (unitOfWorkResult) {
       // transaction is complete. Use uowResult to check the result
   })
   .catch( function( error ) {
       // Server reported an error.
   });

const unitOfWork = new Backendless.UnitOfWork();

// This is an array for child objects.
// They are referenced using objectId values.
// The example hard-codes the array, but in
// your code you'd get the objectId values
// from your data model or using a query
const gifts = [
   new Gift({"objectId" : "EE3BF4B5-DB88-1425-FF89-CC11B7707500"}),
   new Gift({"objectId" : "0CF23E36-FCC0-4E04-FF3E-8B67E6E27200"})
]


// this is the objectId of the parent object.
const personObjectId = {"objectId" : "E7AD83E0-1B4E-D250-FF46-61BFAB18D700"}


// the name of the table where the parent object is stored
const parentTableName = "Person";

// the name of the relation column
const relationColumnName = "wishlist";

// add the deleteRelation call to the transaction
unitOfWork.deleteRelation( parentTableName,
                           personObjectId,
                           relationColumnName,
                           gifts );

// run the transaction
unitOfWork.execute()
   .then(function (unitOfWorkResult) {
       // transaction is complete. Use uowResult to check the result
   })
   .catch( function( error ) {
       // Server reported an error.
   });
The Gift class is shown below:
function Gift(args) {
    args = args || {};
    this.objectId = args.objectId || "";
    this.name = args.name || "";
    this.price = args.price || "";
}

const unitOfWork = new Backendless.UnitOfWork();

// compose a query to fetch the gift objects
const queryBuilder = Backendless.DataQueryBuilder.create();
queryBuilder.setWhereClause("name in ( 'Apple iPad', 'Apple iPhone', 'Selfie Stick')" );

// add the find operation to the transaction
// notice the result of the operation is saved in a constiable -
// it will be used further in the setRelation operation
const gifts = unitOfWork.find("Gift", queryBuilder);

// this is the objectId of the parent object.
const personObjectId = {"objectId" : "E7AD83E0-1B4E-D250-FF46-61BFAB18D700"}

// the name of the table where the parent object is stored
const parentTableName = "Person";

// the name of the relation column
const relationColumnName = "wishlist";

// add the deleteRelation call to the transaction
unitOfWork.deleteRelation( parentTableName,
                           personObjectId,
                           relationColumnName,
                           gifts );

// run the transaction
unitOfWork.execute()
   .then(function (unitOfWorkResult) {
       // transaction is complete. Use uowResult to check the result
   })
   .catch( function( error ) {
       // Server reported an error.
   });

The child objects are represented as

const unitOfWork = new Backendless.UnitOfWork();

// This is an array for child objects.
// They are referenced using objectId values.
// The example hard-codes the array, but in
// your code you'd get the objectId values
// from your data model or using a query
const giftIds = [ 
  "EE3BF4B5-DB88-1425-FF89-CC11B7707500",
  "0CF23E36-FCC0-4E04-FF3E-8B67E6E27200",
  "DFFEDE1D-E423-2472-FF71-26EEC3F23700" 
]

// this is the objectId of the parent object.
const personObjectId = new Person({"objectId" : "E7AD83E0-1B4E-D250-FF46-61BFAB18D700"});

// the name of the table where the parent object is stored
const parentTableName = "Person";

// the name of the relation column
const relationColumnName = "wishlist";

// add the deleteRelation call to the transaction
unitOfWork.deleteRelation( parentTableName,
                          personObjectId,
                          relationColumnName,
                          giftIds );

// run the transaction
unitOfWork.execute()
   .then(function (unitOfWorkResult) {
       // transaction is complete. Use uowResult to check the result
   })
   .catch( function( error ) {
       // Server reported an error.
   });

const unitOfWork = new Backendless.UnitOfWork();

// This is a list of gift objects. These objects
// will be children in the relationship. As you
// can see the objects are constructed manually
// and their objectId's are set, however, in your
// application they would be loaded from the
// server. This is done here to keep the example
// more succinct.
const gifts = [
   {"objectId" : "EE3BF4B5-DB88-1425-FF89-CC11B7707500"},
   {"objectId" : "0CF23E36-FCC0-4E04-FF3E-8B67E6E27200"}
]

// this is the objectId of the parent object.
const personObjectId = new Person({"objectId" : "E7AD83E0-1B4E-D250-FF46-61BFAB18D700"});

// the name of the table where the parent object is stored
const parentTableName = "Person";

// the name of the relation column
const relationColumnName = "wishlist";

// add the deleteRelation call to the transaction
unitOfWork.deleteRelation( parentTableName,
                           personObjectId,
                          relationColumnName,
                          gifts );

// run the transaction
unitOfWork.execute()
   .then(function (unitOfWorkResult) {
       // transaction is complete. Use uowResult to check the result
   })
   .catch( function( error ) {
       // Server reported an error.
   });

const unitOfWork = new Backendless.UnitOfWork();

// This is an array for child objects.
// They are referenced using objectId values.
// The example hard-codes the array, but in
// your code you'd get the objectId values
// from your data model or using a query
const gifts = [
   new Gift({"objectId" : "EE3BF4B5-DB88-1425-FF89-CC11B7707500"}),
   new Gift({"objectId" : "0CF23E36-FCC0-4E04-FF3E-8B67E6E27200"})
]


// this is the objectId of the parent object.
const personObjectId = new Person({"objectId" : "E7AD83E0-1B4E-D250-FF46-61BFAB18D700"});

// the name of the table where the parent object is stored
const parentTableName = "Person";

// the name of the relation column
const relationColumnName = "wishlist";

// add the deleteRelation call to the transaction
unitOfWork.deleteRelation( parentTableName,
                           personObjectId,
                           relationColumnName,
                           gifts );

// run the transaction
unitOfWork.execute()
   .then(function (unitOfWorkResult) {
       // transaction is complete. Use uowResult to check the result
   })
   .catch( function( error ) {
       // Server reported an error.
   });
The Gift class is shown below:
function Gift(args) {
    args = args || {};
    this.objectId = args.objectId || "";
    this.name = args.name || "";
    this.price = args.price || "";
}

const unitOfWork = new Backendless.UnitOfWork();

// compose a query to fetch the gift objects
const queryBuilder = Backendless.DataQueryBuilder.create();
queryBuilder.setWhereClause("name in ( 'Apple iPad', 'Apple iPhone', 'Selfie Stick')" );

// add the find operation to the transaction
// notice the result of the operation is saved in a constiable -
// it will be used further in the setRelation operation
const gifts = unitOfWork.find("Gift", queryBuilder);

// this is the objectId of the parent object.
const personObjectId = new Person({"objectId" : "E7AD83E0-1B4E-D250-FF46-61BFAB18D700"});

// the name of the table where the parent object is stored
const parentTableName = "Person";

// the name of the relation column
const relationColumnName = "wishlist";

// add the deleteRelation call to the transaction
unitOfWork.deleteRelation( parentTableName,
                           personObjectId,
                           relationColumnName,
                           gifts );

// run the transaction
unitOfWork.execute()
   .then(function (unitOfWorkResult) {
       // transaction is complete. Use uowResult to check the result
   })
   .catch( function( error ) {
       // Server reported an error.
   });

The child objects are represented as

const unitOfWork = new Backendless.UnitOfWork();

// This is an array for child objects.
// They are referenced using objectId values.
// The example hard-codes the array, but in
// your code you'd get the objectId values
// from your data model or using a query
const giftIds = [
   "EE3BF4B5-DB88-1425-FF89-CC11B7707500",
   "0CF23E36-FCC0-4E04-FF3E-8B67E6E27200",
   "DFFEDE1D-E423-2472-FF71-26EEC3F23700"
]


// compose a query to retrieve the person
// from the database
const queryBuilder = Backendless.DataQueryBuilder.create();
// this is the query which identifies the person of interest,
// this person object will be used as the parent in the relationship
queryBuilder.setWhereClause( "name = 'John Doe' and age = 36" );

// add the object retrieval operation to the transaction
const findResult = unitOfWork.find( "Person", queryBuilder );

// since "findResult" references a collection of objects,
// get the first one from the collection. The reason we need to
// do this is because the setRelation operation below
// expects only one parent object. We know the first object
// will be the parent, that's why the "resolveTo" index is 0.
const parentObjectRef = findResult.resolveTo( 0 );

// the name of the relation column
const relationColumnName = "wishlist";

// add the deleteRelation call to the transaction
unitOfWork.deleteRelation( parentObjectRef,
                           relationColumnName,
                           giftIds );

// run the transaction
unitOfWork.execute()
   .then(function (unitOfWorkResult) {
       // transaction is complete. Use uowResult to check the result
   })
   .catch( function( error ) {
       // Server reported an error.
   });

const unitOfWork = new Backendless.UnitOfWork();

// This is a list of gift objects. These objects
// will be children in the relationship. As you
// can see the objects are constructed manually
// and their objectId's are set, however, in your
// application they would be loaded from the
// server. This is done here to keep the example
// more succinct.
const gifts = [
   {"objectId" : "EE3BF4B5-DB88-1425-FF89-CC11B7707500"},
   {"objectId" : "0CF23E36-FCC0-4E04-FF3E-8B67E6E27200"}
]

// compose a query to retrieve the person
// from the database
const queryBuilder = Backendless.DataQueryBuilder.create();
// this is the query which identifies the person of interest,
// this person object will be used as the parent in the relationship
queryBuilder.setWhereClause( "name = 'John Doe' and age = 36" );

// add the object retrieval operation to the transaction
const findResult = unitOfWork.find( "Person", queryBuilder );

// since "findResult" references a collection of objects,
// get the first one from the collection. The reason we need to
// do this is because the setRelation operation below
// expects only one parent object. We know the first object
// will be the parent, that's why the "resolveTo" index is 0.
const parentObjectRef = findResult.resolveTo( 0 );

// the name of the relation column
const relationColumnName = "wishlist";

// add the deleteRelation call to the transaction
unitOfWork.deleteRelation( parentObjectRef,
                           relationColumnName,
                           gifts );

// run the transaction
unitOfWork.execute()
   .then(function (unitOfWorkResult) {
       // transaction is complete. Use uowResult to check the result
   })
   .catch( function( error ) {
       // Server reported an error.
   });

const unitOfWork = new Backendless.UnitOfWork();

// This is an array for child objects.
// They are referenced using objectId values.
// The example hard-codes the array, but in
// your code you'd get the objectId values
// from your data model or using a query
const gifts = [
   new Gift({"objectId" : "EE3BF4B5-DB88-1425-FF89-CC11B7707500"}),
   new Gift({"objectId" : "0CF23E36-FCC0-4E04-FF3E-8B67E6E27200"})
]


// compose a query to retrieve the person
// from the database
const queryBuilder = Backendless.DataQueryBuilder.create();
// this is the query which identifies the person of interest,
// this person object will be used as the parent in the relationship
queryBuilder.setWhereClause( "name = 'John Doe' and age = 36" );

// add the object retrieval operation to the transaction
const findResult = unitOfWork.find( "Person", queryBuilder );

// since "findResult" references a collection of objects,
// get the first one from the collection. The reason we need to
// do this is because the setRelation operation below
// expects only one parent object. We know the first object
// will be the parent, that's why the "resolveTo" index is 0.
const parentObjectRef = findResult.resolveTo( 0 );

// the name of the relation column
const relationColumnName = "wishlist";

// add the deleteRelation call to the transaction
unitOfWork.deleteRelation( parentObjectRef,
                           relationColumnName,
                           gifts );

// run the transaction
unitOfWork.execute()
   .then(function (unitOfWorkResult) {
       // transaction is complete. Use uowResult to check the result
   })
   .catch( function( error ) {
       // Server reported an error.
   });
The Gift class is shown below:
function Gift(args) {
    args = args || {};
    this.objectId = args.objectId || "";
    this.name = args.name || "";
    this.price = args.price || "";
}

const unitOfWork = new Backendless.UnitOfWork();

// compose a query to fetch the gift objects
const queryBuilder = Backendless.DataQueryBuilder.create();
queryBuilder.setWhereClause("name in ( 'Apple iPad', 'Apple iPhone', 'Selfie Stick')" );

// add the find operation to the transaction
// notice the result of the operation is saved in a constiable -
// it will be used further in the setRelation operation
const gifts = unitOfWork.find("Gift", queryBuilder);

// compose a query to retrieve the person
// from the database
const queryBuilder = Backendless.DataQueryBuilder.create();

// this is the query which identifies the person of interest,
// this person object will be used as the parent in the relationship
queryBuilder.setWhereClause( "name = 'John Doe' and age = 36" );

// add the object retrieval operation to the transaction
const findResult = unitOfWork.find( "Person", queryBuilder );

// since "findResult" references a collection of objects,
// get the first one from the collection. The reason we need to
// do this is because the setRelation operation below
// expects only one parent object. We know the first object
// will be the parent, that's why the "resolveTo" index is 0.
const parentObjectRef = findResult.resolveTo( 0 );

// the name of the relation column
const relationColumnName = "wishlist";

// add the deleteRelation call to the transaction
unitOfWork.deleteRelation( parentObjectRef,
                           relationColumnName,
                           gifts );

// run the transaction
unitOfWork.execute()
   .then(function (unitOfWorkResult) {
       // transaction is complete. Use uowResult to check the result
   })
   .catch( function( error ) {
       // Server reported an error.
   });