Correct Memory Management for [string UTF8String]

Question

I'm somewhat new to objective-c and I'm not sure what the correct memory management for this code is.

const unsigned char * data =(const unsigned char *) [string UTF8String];

When I call free on data I get an error. Do I need to clean up after this call?

thanks!

Answer 1

No. "UTF8String" does not contain the words alloc, copy, retain, or create. Thus, you're not responsible for that memory.

Note that if you want that data to stick around after string is released, you should copy it; by the contract, you're not responsible for that memory, but you are also not guaranteed that it will last beyond the scope of the object that gave it to you.

Answer 2

You do not need to free it.

In Cocoa, if a method does not contain the words alloc, init, or copy, you do not own the object that is returned from said method.

-UTF8String actually points to the cstring representation of the NSString object you are calling it on. When the object's state changes, the UTF8String also changes.

Answer 3

As stated in the documentation, it is automatically freed the same way an autoreleased object would be.

Answer 4

technically speaking, free() is used to remove memory allocated using malloc() from the heap. malloc() was not used to allocate the memory. remember that objective-c is c with extensions. the data variable will remain in memory based on the c language 'scoping' rules.