Copy & Mutablecopy

Copy & Mutablecopy

Copy & Mutablecopy

Use the copy or Mutablecopy method to create a copy of an object

Copy

Need to implement Nscoppying protocol

Immutable replicas are created (such as NSString, Nsarray, Nsdictionary)

Mutablecopy

Need to implement the Nsmutablecopying protocol first

A mutable copy is created (such as nsmutablestring, Nsmutablearray, Nsmutabledictionary)

The purpose of copy is to create a copy, while modifying the original object and copy without interfering with each other

Deep Copy & Sneak copy

Deep copy:

Content copy, the source object and the copy point to a different two objects

The source object reference counter is unchanged, and the replica counter is set to 1

Shallow copy:

Pointer copy, source object and copy point to the same object

Object reference counter +1 is actually equivalent to doing a retain operation

Only immutable objects Create immutable replicas (copy) is shallow copy, others are deep copy

Copywithzone of Custom objects

-(ID) Copywithzone: (Nszone *) zone

{

Person *p = [[[Self class] allocwithzone:zone] init];

P.name = Self.name;

P.age = Self.age;

return p;

}

About NSNumber & int Nsinteger

Int is in the stack area, high efficiency, fast, can be put in the method of internal use

NSNumber is the object, in the heap, with the function of numerical conversion, the efficiency is poor, convenient KVC assignment

Q & A

Copy & Mutablecopy