iOS An Obj C question

[multinode]

Can someone please tell me the difference between

class method

NSString * = stringWithCString:(const char *)cString encoding:(NSStringEncoding)enc       

Return Value
A string containing the characters described in cString.

and

instance method

NSString * = [[NSString alloc] initWithCString:(const char *)nullTerminatedCString encoding:(NSStringEncoding)encoding

Return Value
An NSString object initialized using the characters from nullTerminatedCString.

I am assuming that in both cases memory is allocated for the returned NSString object ... is that correct?

Thank you.

 

[yaniv92648]

Differences

1. Class Method: memory here is allocated but by the class method itself and not directly by u. so u don't release the memory.
2. Instance Method: memory here is allocated by u directly. so u must release the memory.

 

[multinode]

1. Class Method: memory here is allocated but by the class method itself and not directly by u. so u don't release the memory.
2. Instance Method: memory here is allocated by u directly. so u must release the memory.

Thanx ... so when should I use the first way and when should I use the second way?

 

[yaniv92648]

Well..

BTW, class method is called "convenience method" (cuz it takes care of the object releasing 4 u). Apple docs recommend using convenience methods alone. if u must - use instance methods.

 

[multinode]

BTW, class method is called "convenience method" (cuz it takes care of the object releasing 4 u). Apple docs recommend using convenience methods alone. if u must - use instance methods.

Thanx Yaniv.

 

[dantastic]

Is the recommendation really to use convenience methods? I was of the understanding that, at least on the memory constrained iPhone, the preferred way is not to use them.

 

[yaniv92648]

i looked it up in the docs..

but couldn't find it..
though i remember reading it's better 2 use convenience constructors - i don't c it now. i actually didn't c any preference 2 convenience constructors or alloc.

 

[chown33]

The difference between the two methods is that you own the object resulting from alloc, but you don't own the one returned by the convenience method.

http://developer.apple.com/library/ios/#documentation/cocoa/Conceptual/MemoryMgmt/MemoryMgmt.html

There is no other significant difference.