Question

I’m having a strange problem while using NSDictionnary …

I’m trying to retrieve an object for a key that is present is the dictionnary with the method objectForKey, but it returns nil instead.

When I print out the whole dictionnary, I can see clearly the key and the value I’m looking for.

Here is the code :

- (MObject *)GetWithMProperty:(MProperty *)prop {
    NSLog(@"We search an object for a property named %@", prop.Name);
    NSArray *keyArray =  [_dict allKeys];
    int count = [keyArray count];
    for (int i=0; i < count; i++) {
        MObject *tmp = [_dict objectForKey:[ keyArray objectAtIndex:i]];
        NSLog(@"Key = %@ | Object = %d", ((MProperty*)[keyArray objectAtIndex:i]).Name, tmp.GetTypeId);
        if (prop == [keyArray objectAtIndex:i])
            NSLog(@"Wouhou !");
        else
            NSLog(@"Too bad :(");
    }
    return [_dict objectForKey:prop];
}

And the stack trace :

2012-10-29 11:24:07.730 IOS6[1451:11303] We search an object for a property named Value
2012-10-29 11:24:07.730 IOS6[1451:11303] Key = Name | Object = 4
2012-10-29 11:24:07.731 IOS6[1451:11303] Too bad :(
2012-10-29 11:24:07.731 IOS6[1451:11303] Key = Value | Object = 0
2012-10-29 11:24:07.732 IOS6[1451:11303] Too bad :(

It’s a bit complicated, I’m using J2ObjC to compile a fully functional Engine, and thus I can’t modify the classes MProperty and MObject (used by the Engine).

MProperty doesn’t conforms to NSCopying protocol, so I created a classe called IPhoneMProperty that inherits from MProperty and conforms to the protocol.

Here is this class :

@implementation IPhoneMProperty

- (id)initWithMProperty:(MProperty *)prop {
    self = [super initWithInt:prop.OwnerTypeId withNSString:prop.Name withInt:prop.TypeId withMBasicValue:prop.DefaultValue withInt:prop.Flags];
    return self;
}

- (id)copyWithZone:(NSZone *)zone {
    IPhoneMProperty *prop = [[IPhoneMProperty alloc] initWithMProperty:self];
    return prop;
}

@end

And the method I use to add object and keys to the dictionnary :

- (void)SetWithMProperty:(MProperty *)prop withMObject:(MObject *)obj {
    IPhoneMProperty *tempKey = [[IPhoneMProperty alloc] initWithMProperty:prop];
    [_dict setObject:obj forKey:tempKey];
}

I hope it’s clear enough, actually it’s the only solution I found for the moment, but it doesn’t work 🙁

Can anyone helps me with this ?

Thanks !

Answer 1

The problem exists in the line

    if (prop == [keyArray objectAtIndex:i])

Instead, implement isEquals: method in your MProperty class.

-(BOOL)isEquals:(MProperty*)inProp {
  if( [inProp.name isEqualToString:self.name] )return YES;

  return NO;
}

And, here, instead of the line

    if (prop == [keyArray objectAtIndex:i])

use the following line,

    if ([prop isEquals [keyArray objectAtIndex:i]])