Delete Relation using condition¶
The API deletes objects from a relationship with their parent. The objects are identified implicitly through a whereClause
condition.
Blocking API¶
int result = Backendless.Data.Of( "TABLE-NAME" ).DeleteRelation( Dictionary<string, object> parentObject, string relationColumnName, string whereClause );
int result = Backendless.Data.Of<E>().DeleteRelation( E parentObject, string relationColumnName, string whereClause );
Non-Blocking API¶
Backendless.Data.Of( "TABLE-NAME" ).DeleteRelation( Dictionary<string, object> parentObject, string relationColumnName, string whereClause, AsyncCallback<int> callback );
Backendless.Data.Of<E>().DeleteRelation( E parentObject, string relationColumnName, string whereClause, 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 identified 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 representing the relation. Relationship between the child objects identified by whereClause will be deleted for this column in parentObject . |
whereClause |
a where clause condition identifying the objects in the child table which will be removed from the relation to the parent object. |
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 removed from the relationship. The asynchronous call receives the return value through a callback executed on the AsyncCallback
object.
Example¶
The following example deletes a relation between a Person
object and all the related objects in the related table identified by column "user"
which match the provided query:
name='Joe' or name = 'Frank'
As a result of the operation, all related objects where the name
property is either Joe
or Frank
will be deleted from the relation.
Dictionary<string, object> parentObject = new Dictionary<string, object>(); parentObject[ "objectId" ] = "41230622-DC4D-204F-FF5A-F893A0324800"; 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, "user", "name = \"Joe\" or name = \"Frank\"", deleteRelationCallback );
Person personObject = // personObject retrieval is out of scope in this example 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, "user", "name = \"Joe\" or name = \"Frank\"", deleteRelationCallback );