正确的内存管理[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?

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

如文档中所述，它会自动释放自动释放对象的方式。

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.