Objective-C: 12_copy

A copy of an object can be created using the copy or nutablecopy method. The original object is not affected when the copy is modified. Copy : Must be implemented first Nscopying Protocol , Creating an immutable copy (Such as nsstring, nsarray, and nsdictionary) Mutablecopy : Must be implemented first Nsmutablecopying Protocol , A mutable copy is created. (Such as nsmutablestring, nsmutablearray, and nsmutable) Deep copy: the source object and copy point to two different objects. The Reference Counter of the object remains unchanged, and the copy counter is set to 1 Copy: pointer copy. The source object and copy point to the same object. The Reference Counter of the object is + 1, which is equivalent to a retain operation. Only the immutable object that creates an immutable copy is the shortest copy. Mutablecopy is also a deep copy. Nsstring * string = [[nsstring alloc] initwithformat: @ "Age is % d", 10]; nsmutablestring * STR = [String mutablecopy]; Copy generates an immutable copy. Because the source object itself is immutable, copy directly returns the source object for the sake of performance. The source object counter will be + 1 Nsstring * STR = [String Copy];

Objective-C: 12_copy