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Re: No sure way to tell whether an array is mutable?
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Re: No sure way to tell whether an array is mutable?


  • Subject: Re: No sure way to tell whether an array is mutable?
  • From: Jeff C <email@hidden>
  • Date: Thu, 25 Jan 2007 22:02:29 -0500

If an object says that a return value is an NSMutableArray and you get back an NSArray, then something is broken. You can't even claim polymorphism, since a superclass cannot masquerade as a subclass.

I think your problem lies elsewhere.

I have been known to lose my brains and do this:

NSMutableArray *theArray=[[NSArray alloc] init];

which leads to bad things down the line, similar to what you're seeing.

On Jan 25, 2007, at 9:21 PM, Kenny Leung wrote:

Hi All.

I think I have just been burned by something sinister: an object says that it is an NSMutableArray, but turns out to be non-mutable. I'm wondering if anyone has run into this:

code snippet:

    if ( [newChildren isKindOfClass:[NSMutableArray class]] ) {
        HXDebug(@"Mutable:%@", newChildren);
    }
    [newChildren insertObject:entry atIndex:newIndex];

output:

DEBUG Mutable:()
*** -[NSCFArray insertObject:atIndex:]: mutating method sent to immutable object


Thanks for any insight!

-Kenny

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  • Follow-Ups:
    • Re: No sure way to tell whether an array is mutable?
      • From: Sam DeVore <email@hidden>
References: 
 >No sure way to tell whether an array is mutable? (From: Kenny Leung <email@hidden>)

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