NSManagedObject setValue forKey在线程中循环

Question

I'm trying to save some data into database using CoreData so I created Entity named 'Client' with some attributes. Two of them are 'city' and 'post_code', both of String type. I also created Client class extending NSManagedObjects and I wrote some methods there.

-(void) setCity: (NSString*) city
{
    [self setValue:city forKey:@"city"];
}

-(NSString*) getCity
{
    return [self valueForKey:@"city"];
}

-(void) setPostCode: (NSString*) postCode
{
    [self setValue:postCode forKey:@"post_code"];
}

-(NSString*) getPostCode
{
    return [self valueForKey:@"post_code"];
}

getPostCode and setPostCode work as I expected but calling setCity or getCity is causing problems. Appication stops and method is looping in thread as you can see on screenshot.

Full size image

This is how I call those methods

 if([databaseResult count] > 0)
     c = [databaseResult objectAtIndex:0];
 else
     c = [NSEntityDescription insertNewObjectForEntityForName:@"Client" inManagedObjectContext:context];

[c setPostCode:[jsonData valueForKey:@"post_code_invoice"]];
[c setClientType:[jsonData valueForKey:@"company_type"]];
[c setCity:[jsonData valueForKey:@"city_invoice"]];

it always stops on setCity no matter what data I pass there, even that call doesn't work

[c setCity:@"aaa"];

Did anyone had similar problem?

Answer 1

The setValueForKey method is calling back into the same function because it has the same name.

From the KVC documentation

Default Search Pattern for setValue:forKey:

When the default implementation of setValue:forKey: is invoked for a property the following search pattern is used:

The receiver's class is searched for an accessor method whose name matches the pattern set:.

If no accessor is found, and the receiver's class method accessInstanceVariablesDirectly returns YES, the receiver is searched for an instance variable whose name matches the pattern _, _is, , or is, in that order.

If a matching accessor or instance variable is located, it is used to set the value. If necessary, the value is extracted from the object as described in “Representing Non-Object Values.”

If no appropriate accessor or instance variable is found, setValue:forUndefinedKey: is invoked for the receiver.

So when you call setValue:forKey: with the key city , the implementation calls setCity: and your implementation calls setValue:forKey: , and round and round you go.

Why are you even doing it this way rather than setting the value directly?

Or better still use properties and you don't even need to write setters or getters.

The other two methods work because the key names are different. (they have underscores )