Copy and Mutablecopy notes

Gao Li 228 | Source: Blog Park | 2012/4/22 14:53:20 | Read 4 times

NSString *a = [[NSString alloc]initwithstring:@ "Hello"];
NSString *b = [a copy];
NSLog (@ "%d%d", A.retaincount, B.retaincount);//2,2

Nsmutablestring *f = [a mutablecopy];

NSLog (@ "%d%d", A.retaincount, F.retaincount);//2,1

[F appendstring:@ "DD"];
NSLog (@ "%@,%@", a,f);//Hello,hellodd
//For an immutable object, copy is a shallow copy, but the pointer copies its Retaincount 1
//Mutablecopy is a deep copy is an object copy
    
nsmutablestring *c = [[nsmutablestring alloc]initwithstring:@ "Hello"];
Nsmutablestring *d = [C copy];
NSLog (@ "%d%d", c.retaincount,d.retaincount);//
[D appendstring:@ "ddd"]; Error because copy returns a non-changing object
Nsmutablestring *e = [C mutablecopy];
NSLog (@ "%d%d", c.retaincount,e.retaincount);//
[E appendstring:@ "dddd"];
NSLog (@ "%@,%@", c,e);//HELLO,HELLODDDD
//For mutable objects copy and mutablecopy are both deep copy and copy objects but the object returned by copy is an immutable object
//------------------------------------------------------------//
For System container class objects

Nsarray *array1 = [Nsarray arraywithobjects:@ "a", @ "B", @ "C", nil];
Nsarray *array1copy = [array1 copy];
NSLog (@ "%d,%d", array1.retaincount,array1copy.retaincount);//2,2
Nsmutablearray *arraymcopy = [Array1 mutablecopy];
NSLog (@ "%d,%d", array1.retaincount,arraymcopy.retaincount);//2,1
[Arraymcopy removeobjectatindex:0];
[Arraymcopy addobject:@ "D"];
NSLog (@ "%@-----%@", array1,arraymcopy);//a,b,c-----b,c,d
Nsarray *marray1 = [Nsarray arraywithobjects:[nsmutablestring stringwithstring:@ "A"],@ "B", @ "C", nil];
Nsarray *marray1copy = [mArray1 copy];
NSLog (@ "%d,%d", marray1.retaincount,marray1copy.retaincount);//2,2
Nsmutablearray *marraymcopy = [MArray1 mutablecopy];
NSLog (@ "%d,%d", marray1.retaincount,marraymcopy.retaincount);//2,1
nsmutablestring *temp = [MArray1 objectatindex:0];
NSLog (@ "%@", temp);//a
[Temp appendstring:@ "AA"];
NSLog (@ "%@", mArray1);//AAA b C
NSLog (@ "%@", marray1copy); AAA b C
NSLog (@ "%@", marraymcopy);//AAA b C
//For a container, its element object is always a pointer copy. If you need an element object that is also an object copy, you need to implement a deep copy.
nsarray* Truedeepcopyarray = [Nskeyedunarchiver unarchiveobjectwithdata:
[Nskeyedarchiver Archiveddatawithrootobject:marray1]];
nsmutablestring *TEMP2 = [Truedeepcopyarray objectatindex:0];
[Temp2 appendstring:@ "AA"];

NSLog (@ "%@", mArray1);//AAA b C
NSLog (@ "%@", Truedeepcopyarray);//AAAAA b C
Truedeepcopyarray is a deep copy in full sense.

Copy and Mutablecopy notes