Delete Objects from relation¶

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

Blocking API¶

Using Dictionary

int result = Backendless.Data.Of( "TABLE-NAME" ).DeleteRelation( 
                              Dictionary<string, object> parentObject,
                              string relationColumnName,
                              object[] children );

Custom Class

int result = Backendless.Data.Of<E>().DeleteRelation( 
                            E parentObject,
                            string relationColumnName,
                            object[] children );

Non-Blocking API¶

Using Dictionary

Backendless.Data.Of( "TABLE-NAME" ).DeleteRelation( 
                 Dictionary<string, object> parentObject,
                 string relationColumnName,
                 object[] children,
                 AsyncCallback<int> callback );

Custom Class

Backendless.Data.Of<E>().DeleteRelation( 
                 E parentObject,
                 string relationColumnName,
                 object[] children,
                 AsyncCallback;<int> callback );

where:

Argument	Description
`TABLE-NAME`	Name of the table where the parent object is stored.
`E`	.NET class of the parent object. The class name identifies the table where the parent object is stored.
`parentObject`	The object for which the relation with the specified children will be deleted. When this argument is an instance of `Dictionary<string, object>` (for the dictionary-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`.
`children`	An array of child objects for which the relationship with the `parentObject` will be deleted. Each object must have a valid value for the `objectId` property.
`callback`	a responder object which will receive a callback when the relation has been deleted or if an error occurs. Applies to the asynchronous method only.

Return Value¶

Number of child objects for which the relationship has been deleted. The asynchronous call receives the return value through a callback executed on the AsyncCallback object.

Example¶

The example below deletes a relation between a Person object and its children. The child objects are referenced explicitly in the API call.The relation column is address.

Using Dictionary

Dictionary<string, object> parentObject = new Dictionary<string, object>();
parentObject[ "objectId" ] = "41230622-DC4D-204F-FF5A-F893A0324800";

Dictionary<string, object> childObject1 = new Dictionary<string, object>();
childObject1[ "objectId" ] = "XXXX-XXXX-XXXX-XXXXX";

Dictionary<string, object> childObject2 = new Dictionary<string, object>();
childObject2[ "objectId" ] = "ZZZZ-ZZZZ-ZZZZZ-ZZZZZ";

object[] children = new object[] { childObject1, childObject2 };

AsyncCallback<int> deleteRelationCallback = new AsyncCallback<int>(
  howMany =>
  {
    System.Console.WriteLine( String.Format( "Server has removed {0} objects from the relation", howMany ) );
  },
  error =>
  {
    System.Console.WriteLine( "Server returned an error " + error.Message );
  } );

Backendless.Data.Of( "Person" ).DeleteRelation( 
                  parentObject, 
                  "address", 
                  children, 
                  deleteRelationCallback );

Custom Class

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
object[] childObjects = new object[] { addressObject1, addressObject2 };

AsyncCallback<int> deleteRelationCallback = new AsyncCallback<int>(
  howMany =>
  {
    System.Console.WriteLine( String.Format( "Server has removed {0} objects from the relation", howMany ) );
  },
  error =>
  {
    System.Console.WriteLine( "Server returned an error " + error.Message );
  } );

Backendless.Data.Of<Person>().DeleteRelation( 
                      personObject, 
                      "address", 
                      childObjects,
                      deleteRelationCallback );