Objective-C语法之copy和mutablecopy

#pragma mark 演示字符串的copy

//深拷贝－－对象拷贝－－内容拷贝（产生新对象）新对象计数器＋1，原对象不变
void stringmutableCopy(){
    //string ＝ 1
    NSString *string = [[NSString alloc]initWithFormat:@"age is %i", 10];
    //str ＝ 1
    //产生了一个新对象，原对象的计数器不变
    NSMutableString *str = [string mutableCopy];
    NSLog(@"str:%zi",[string retainCount]);
    NSLog(@"string:%zi",[str retainCount]);

    //修改副本,原对象不变
    [str appendString:@"abcd"];
    NSLog(@"string:%@",string);
    NSLog(@"str:%@",str);

    //string ＝0
    [string release];
    [str release];//copy也需要release
}

//不可变拷不可变－－浅拷贝
//浅拷贝－－指针拷贝－－地址拷贝 （拷贝指针，不会产生新的对象，返回原对象本身，原对象计数器＋1）
void stringcopy(){
    NSString *string = [[NSString alloc]initWithFormat:@"age is %i", 10];
    //为了性能着想，针对copy原则，string本来是不可变，［string copy］并没有产生一个新的对象，而是返回对象本身，copy相当与retain
    NSString *str = [string copy];//产生一个不可变对象
    //NSLog(@"%i", string == str);//结果为1，copy出来的对象为同一个
    NSLog(@"%zi",[string retainCount]);
    NSLog(@"%zi",[str retainCount]);

    [string release];
    [str release];//使用copy或者mutablecopy都需要release
}

#pragma mark 可变字符串的copy
//深拷贝
void mutableStringCopy(){

    NSMutableString *string = [NSMutableString stringWithFormat:@"age is %i",10];

    NSString *str = [string copy];//产生一个不可变的str

    [str release];
}

//深拷贝
void mutableStringmutableCopy(){
    NSMutableString *string = [NSMutableString stringWithFormat:@"age is %i",10];
    //会产生一个新的对象
    NSMutableString *str = [string mutableCopy];
    [str appendString:@"1234"];
    NSLog(@"str:%@",str);
    NSLog(@"string%@",string);
    [str release];

}