CODEWITHSUNDEEP
objective-c
Scrungepipes
Scrungepipes

Reputation: 37581

Calling NSMutableArray:addObject is resulting in an unrecognized selector exception

I'm getting an unrecognized selector exception attempting to call addObject on an array. However my array is an NSMutableArray, not an NSArray. I don't understand why this is happening.

I have the following classes:

@interface A : NSObject
@property (nonatomic, copy)     NSMutableArray* children;
- (id) init;
- (void) addChild: (A*) child;
@end

@interface B : A
- (id) init;
@end

@implementation A
- (id) init 
{ 
   self = [super init];
   return self;
} 

- (void) addChild: (A*) child
{
    [self.children addObject:child];
}
@end


@implementation B
-(id) init 
{
    self = [super init];
    if (self != nil)
    {
           self.children = [[NSMutableArray alloc] init];
    }
    return (self);
}

Then if I create an object of type B and call [b addChild: anObject] I'm getting an unrecognized selector and I don't understand why.

The output is:

2013-04-08 14:31:08.046 otest[13381:7e03] -[__NSArrayI addObject:]: unrecognized selector sent to instance 0x17759c0

What is the problem?

TIA

(Please focus on the actual code and problem, not side discussions why I'm not allocating the array in A's init, unless relevant. I want to understand why the code as it stands does't work. Thanks).

Upvotes: 0

Views: 206

Answers (1)

CodaFi
CodaFi

Reputation: 43330

By declaring the array with the storage qualifier copy instead of strong, your mutable array will be copied on assignment and turned into an immutable NSArray.

Upvotes: 3

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