Re: Synthesize NSMutableString retain count question
Re: Synthesize NSMutableString retain count question
- Subject: Re: Synthesize NSMutableString retain count question
- From: Philip Vallone <email@hidden>
- Date: Wed, 03 Feb 2010 19:19:01 -0500
Thanks.. perfect explanation.
On Feb 3, 2010, at 12:37 PM, Jens Alfke wrote:
>
> On Feb 3, 2010, at 3:55 AM, Philip Vallone wrote:
>
>> currentSection = @"Some value";
>> The retain count goes to 1
>
> This assigns a new value to the pointer variable 'currentSection'. It now points to the immutable string literal @"Some value".
>
>> However if I assign a value with
>> [currentSection setString:@"Some value"];
>> The retain count is still zero.
>
> This tells the mutable string object that 'currentSection' currently points to, to replace its contents with the characters in the string @"Some value".
>
> If you find the retain count is zero after this, it's probably because the value of 'currentSection' is nil, i.e. it doesn't point to any object. In that case the -setString: message is a no-op since messages to nil are ignored, and -retainCount will return zero because messages to nil always return 0/nil.
>
> In general, it sounds as though you're unclear on the distinction between an object and a pointer to an object. It's the same as structs vs. pointers to structs in C, or for objects in C++; the difference is that Objective-C objects can only be referred to by pointers (you can't have a variable of type "NSString", only "NSString*".)
>
> —Jens
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