Objective-C文法之copy和mutablecopy

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#pragma mark 示範字串的copy//深拷貝－－對象拷貝－－內容拷貝（產生新對象）新對象計數器＋1，原對象不變void stringmutableCopy(){    //string ＝ 1    NSString *string = [[NSString alloc]initWithFormat:@"age is %i", 10];    //str ＝ 1    //產生了一個新對象，原對象的計數器不變    NSMutableString *str = [string mutableCopy];    NSLog(@"str:%zi",[string retainCount]);    NSLog(@"string:%zi",[str retainCount]);        //修改副本,原對象不變    [str appendString:@"abcd"];    NSLog(@"string:%@",string);    NSLog(@"str:%@",str);            //string ＝0    [string release];    [str release];//copy也需要release}//不可變拷不可變－－淺拷貝//淺拷貝－－指標拷貝－－地址拷貝 （拷貝指標，不會產生新的對象，返回原對象本身，原對象計數器＋1）void stringcopy(){    NSString *string = [[NSString alloc]initWithFormat:@"age is %i", 10];    //為了效能著想，針對copy原則，string本來是不可變，［string copy］並沒有產生一個新的對象，而是返回對象本身，copy相當與retain    NSString *str = [string copy];//產生一個不可變對象    //NSLog(@"%i", string == str);//結果為1，copy出來的對象為同一個    NSLog(@"%zi",[string retainCount]);    NSLog(@"%zi",[str retainCount]);        [string release];    [str release];//使用copy或者mutablecopy都需要release}#pragma mark 可變字串的copy//深拷貝void mutableStringCopy(){        NSMutableString *string = [NSMutableString stringWithFormat:@"age is %i",10];        NSString *str = [string copy];//產生一個不可變的str        [str release];}//深拷貝void mutableStringmutableCopy(){    NSMutableString *string = [NSMutableString stringWithFormat:@"age is %i",10];    //會產生一個新的對象    NSMutableString *str = [string mutableCopy];    [str appendString:@"1234"];    NSLog(@"str:%@",str);    NSLog(@"string%@",string);    [str release];    }

 

Objective-C文法之copy和mutablecopy