Delete Objects from relation

The API removes specific objects from a relationship with their parent.

Method

Using MapCustom Class

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

Future<int> Backendless.data.withClass<E>(). deleteRelation(
                     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 for which the relation with the specified children will be deleted. 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. Relationship between the specified objects from the children collection will be deleted for the column in parentObject.
childrenObjectIds	A collection of child object IDs for which the relationship with the parentObject will be deleted.

Return Value

Number of child objects for which the relationship has been deleted.

Example

The example below deletes a relation between a Person object and its children. The child objects are referenced explicitly in the API call (see the object IDs in the collection as "XXXXX-XXXXX-XXXXX-XXXXX" ``and`` "ZZZZ-ZZZZ-ZZZZZ-ZZZZZ").The relation column is address.

Using MapCustom Class

Map parentObject = // parentObject retrieval is out of scope in this example
Map childObject1 = // childObject retrieval is out of scope in this example
Map childObject2 = // childObject retrieval is out of scope in this example

Backendless.data.of("Person"). deleteRelation(parentObject['objectId'], "address", 
  children: [childObject1['objectId'], childObject2['objectId']]).then((response) {
    // relation has been deleted
});

Person personObject = // personObject retrieval is out of scope in this example
Address addressObject1 = // addressObject retrieval is out of scope in this example
Address addressObject2 = // addressObject retrieval is out of scope in this example

Backendless.data.withClass<Person>(). deleteRelation(personObject.objectId, "address", 
  children: [addressObject1.objectId, addressObject2.objectId]).then((response) {
    // relation has been deleted
});

Codeless Reference

where:

Argument	Description
table name	Name of the table where which contains the parent object as identified by parent object.
parent object	Id of the object for which the relation will be deleted.
relation name	Name of the column which identifies the relation within the parent table (identified as table name).
children	Represents a list containing unique identifiers(objectIds) of the children objects relations that must be deleted from the data table.
return result	When this box is checked, the operation returns the number of removed child objects relations.

Returns the number of removed child objects relations.

Consider the first object with one-to-many relations(skills column) in the parent data table called employees:

By clicking the record (1:N Relations) in the skills column of the parent data table presented above, you get redirected to the child data table called uniqueSkills, where you can see the related children objects:

Suppose you want to remove two relations. The following example demonstrates the removal of the Objective-C and Javascript relations from the parent object:

The objectId values for each relation are:

1. Objective-C: "4E205196-59B0-45A6-BACB-303A66BEFF22"

2. Javascript: "D08FA6A7-4534-4B43-AF06-BC4CBFE54C60"

After the operation runs, the Objective-C and Javascript relations get deleted.