#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];    }