Add Relation using condition¶

This API request adds related objects to the existing collection. Child objects to add to the relation are defined through a whereClause condition.

Method¶

Using Map

Future<int> Backendless.data.of("TABLE-NAME").addRelation(
                   String parentObjectId, 
                   String relationColumnName, 
                  {List<String> childrenObjectIds, 
                   String whereClause});

Custom Class

Future<int> Backendless.data.withClass<E>().addRelation(
                    String parentObjectId, 
                    String relationColumnName,
                   {List<String> childrenObjectIds, 
                    String whereClause});

where:

Argument	Description
`TABLE-NAME`	Name of the table where the parent object is stored.
`E`	Dart class of the parent object. The class name identifies the table where the parent object is stored.
`parentObjectId`	The ID of an object which will be assigned related children for `relatedColumnName`. When this argument is an instance of `Map` (for the map-based approach), it must contain the `"objectId"` property.
`relationColumnName`	Name of the column identifying the relation. Objects from the `children` collection will be added as related for the column in `parentObject`. The column name may optionally include table name separated by the colon character as well as cardinality which determines the type of relationship (one to one or one to many) (see the note below):

Important

If the column does not exist in the parent table at the time when the API is called, the value of the "relationColumnName" argument must include the name of the child table separated by colon and the cardinality notation. The cardinality is expressed as ":1" for one-to-one relations and ":n" for one-to-many relations. For example, the value of "myOrder:Order:1" will create a one-to-one relation column "myOrder" in the parent table. The column will point to the Order child table. Likewise, the value of "myOrder:Order:n" will create a one-to-many relation column "myOrder" pointing to the Order table.

Argument	Description
`whereClause`	a where clause condition identifying objects in the child table which will be added as related objects to the parent object.

Return Value¶

Number of child objects added to the relation.

Example¶

The following request adds objects from the Users table to a related property/column the Person object. Child objects added to the relation must match the provided query. The query is specified in the whereClause argument:

name='Joe' or name = 'Frank'.

As a result of the operation, all User objects where the name property is either Joe or Frank will be added to the relation. The relation column is created if it does not exist. This is done because the column contains the child table qualifier, defined as ":Users" right after the column name.

Using Map

Map parentObject = // parentObject retrieval is out of scope in this example

Backendless.data.of("Person").addRelation(parentObject['objectId'], "users:Users:n", 
  whereClause: 'name = "Joe" or name = "Frank"').then((response) {
    // related object has been added
});

Custom Class

Person personObject = // personObject retrieval is out of scope in this example

Backendless.data.withClass<Person>().addRelation(personObject.objectId, "users:Users:n", 
  whereClause: 'name = "Joe" or name = "Frank"').then((response) {
    // related object has been added
});