CoreData - How to use validateForDelete: to determine if a managed entity should be deleted

Question

Purpose: I want to check the managed entity to make sure that it is ok to delete

Pending: -[NSManagedObject validateForDelete:] should return BOOLbased on the configuration of deletion rules in the managed object model

---

Class reference NSManagedObject

validateForDelete:

Determines whether the receiver can be deleted in the current state.

- (BOOL)validateForDelete:(NSError **)error

Parameters

Mistake

If the recipient cannot be deleted in its current state, it returns an NSError instance on return, which describes the problem.

Return value

YESif the receiver can be deleted in the current state, otherwise NO.

Discussion

An object cannot be deleted if it has a relationship, has a deny deletion rule, and that relationship has a destination.

Implementation

NSManagedObject s sends a description of the recipient entity to a message that performs a basic check based on the presence or absence of values.

Reading this, I guess I should do something like this:

BOOL canDelete = [myManagedObject validateForDelete:&error];

if (canDelete) {
    [managedObjectContext deleteObject:myManagedObject];
}
else {
    [self requestUserFeedback];
}

However, this method almost always returns NO.

---

Code example

Managed Object Model

Department
 - Attribute: name  
     - Value: String
 - Relationship: employees
     - To Many
     - Destination: Employee
     - Delete Rule: Nullify
     - Inverse: department

Employee
 - Attribute: name
     - Value: String
 - Relationship: department
     - To One
     - Destination: Department
     - Delete Rule: Nullify
     - Inverse: employees

Code example:

NSManagedObject *department = [NSEntityDescription insertNewObjectForEntityForName:@"Department" inManagedObjectContext:self.managedObjectContext];

for (int i = 0; i < 10; i++) {
    NSManagedObject *employee = [NSEntityDescription insertNewObjectForEntityForName:@"Employee" inManagedObjectContext:self.managedObjectContext];
    [employee setValue:department forKey:@"department"];
    if ([employee validateForDelete:NULL]) {
        NSLog(@"Can delete employee");
    }
    else {
        NSLog(@"WARNING: Cannot delete employee");
    }
}

NSError *error;
BOOL canDelete = [department validateForDelete:&error];
if (canDelete) {
    NSLog(@"Can delete department");
}
else {
    NSLog(@"WARNING: Cannot delete department");
}

Output:

:

, canDelete - NO. , ? ()

Error Domain=NSCocoaErrorDomain
Code=1600
UserInfo= <>{
    NSValidationErrorObject=< department object >
    NSValidationErrorKey=employees
    NSValidationErrorValue=Relationship 'employees' on managed object
}

, validateForDelete: , "", "". :

, , [sic] "deny" , .

NSManagedObjects , , .

, validateForDelete : , "deny" . "--".

---

Google Apple 2009 , : -[NSManagedObject validateForDelete:] - , , , .

? ? , :

, .

---

, , ?

- GitHub, , .

Answer 1

, , , , super, .

, -validateForDelete: NO .

, " ", .

/, , YES. , .