Set Relation with objects¶
API request replaces related objects with the ones identified in the API call. Child objects must be explicitly defined by referencing their IDs.
- (void)setRelationWithColumnName:(NSString * _Nonnull)columnName parentObjectId:(NSString * _Nonnull)parentObjectId childrenObjectIds:(NSArray<NSString *> * _Nonnull)childrenObjectIds responseHandler:^(NSNumber * _Nonnull)responseHandler errorHandler:^(Fault * _Nonnull)errorHandler;
func setRelation(columnName: String, parentObjectId: String, childrenObjectIds: [String], responseHandler: ((NSNumber) -> Void)!, errorHandler: ((Fault) -> Void)!)
- (void)setRelationWithColumnName:(NSString * _Nonnull)columnName parentObjectId:(NSString * _Nonnull)parentObjectId childrenObjectIds:(NSArray<NSString *> * _Nonnull)childrenObjectIds responseHandler:^(NSNumber * _Nonnull)responseHandler errorHandler:^(Fault * _Nonnull)errorHandler;
func setRelation(columnName: String, parentObjectId: String, childrenObjectIds: [String], responseHandler: ((NSNumber) -> Void)!, errorHandler: ((Fault) -> Void)!)
where:
| Argument | Description |
|---|---|
parentObjectId |
Must be objectId of the object which will be assigned related children for columnName. |
columnName |
Name of the column identifying the relation. Objects from the childObjects collection will be set as related for the column in the table containing parentObjectId. 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 "columnName " 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 |
|---|---|
childrenObjectIds |
A collection of child objectId values to set into the relation. Table of the child objects is identified by columnName. For the one-to-one relations the collection must contain one objectId value. |
Return Value¶
Number of child objects set into the relation.
Example¶
The example below sets a relation for a one-to-one column named address declared in the Person table. The column must be declared in the table prior to the execution of the request shown below. This necessity is explained by missing table name qualifier in the columnName argument - notice the relation column is "address". If the argument value were "address:Address:1", then the column would be created automatically.
DataStoreFactory *dataStore = [Backendless.shared.data of:[Person class]];
[dataStore setRelationWithColumnName:@"address" parentObjectId:@"XXXXX" childrenObjectIds:@[@"YYYYY"] responseHandler:^(NSNumber *relations) {
NSLog(@"Relation has been set");
} errorHandler:^(Fault *fault) {
NSLog(@"Error: %@", fault.message);
}];
let dataStore = Backendless.shared.data.of(Person.self)
dataStore.setRelation(columnName: "address", parentObjectId: "XXXXX", childrenObjectIds: ["YYYYY"], responseHandler: { relations in
print("Relation has been set")
}, errorHandler: { fault in
print("Error: \(fault.message ?? "")")
})
MapDrivenDataStore *dataStore = [Backendless.shared.data ofTable:@"Person"];
[dataStore setRelationWithColumnName:@"address" parentObjectId:@"XXXXX" childrenObjectIds:@[@"YYYYY"] responseHandler:^(NSNumber *relations) {
NSLog(@"Relation has been set");
} errorHandler:^(Fault *fault) {
NSLog(@"Error: %@", fault.message);
}];
let dataStore = Backendless.shared.data.ofTable("Person")
dataStore.setRelation(columnName: "address", parentObjectId: "XXXXX", childrenObjectIds: ["YYYYY"], responseHandler: { relations in
print("Relation has been set")
}, errorHandler: { fault in
print("Error: \(fault.message ?? "")")
})
Codeless Reference¶
The update operation presented further replaces existing objects relations with the new ones.
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 created/set. |
relation name |
Name of the column which identifies the relation within the parent table (identified as table-name). 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):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. |
children |
A list containing unique identifiers(objectId) of the children objects that are used to update existing relations of the parent object. The objectId can be a string value or a number. |
Returns the number of newly set object relations.
The operation requires two data tables to update existing relations. Consider the first object with one-to-many relations(skills column) in the parent data table called employees:
By clicking the value (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 set new relations between the parent object in the employees data table and the third/fifth objects(having values REST and C++) in the uniqueSkills data table presented below:
The example below updates the current relations for the parent object. Children objects that are used to update existing relations:
-
(
skill: REST, objectId: DA9EC928-4B1A-4F57-8C2E-4402D42FE8C9) -
(
skill: C++, objectId: EA8D494F-50D4-445B-8F4E-F6EBC4C39D9F)
As you can see, this operation has replaced the old relations(objects having Javascript and Java values) with the new ones(objects having C++ and REST values):
