1. 概念
浅拷贝：拷贝后，并没有进行真正的复制，拷贝后对象和原对象指向同一个地址
深拷贝：拷贝后对象指向了新的地址
2. 非集合类对象
1. 非集合类不可变对象
NSString *str1 = @"hello world"; NSString *str2 = [str1 copy]; NSString *str3 = [str1 mutableCopy]; NSLog(@"\n str1 = %p class = %@", str1, str1.class); NSLog(@"\n str2 = %p class = %@", str2, str2.class); NSLog(@"\n str3 = %p class = %@", str3, str3.class);
输出
2021-05-08 17:09:47.697211+0800 AlgorithmDemo[33483:14523594] str1 = 0x100008220 class = __NSCFConstantString str2 = 0x100008220 class = __NSCFConstantString str3 = 0x10044f8d0 class = __NSCFString
由打印可得:
- 对于非集合类不可变对象的copy为浅拷贝，mutableCopy为深拷贝
- 浅拷贝获得的对象与原对象地址一致，返回的对象为不可变对象(其实就是原对象)
- 深拷贝返回新的内存地址，返回的对象为可变对象
2. 非集合类可变对象
NSString *str1 = [NSMutableString stringWithString:@"hello world"]; NSMutableString *str2 = [str1 copy]; NSMutableString *str3 = [str1 mutableCopy]; NSLog(@"\n str1 = %p class = %@", str1, str1.class); NSLog(@"\n str2 = %p class = %@", str2, str2.class); NSLog(@"\n str3 = %p class = %@", str3, str3.class);
输出
2021-05-08 17:10:45.047818+0800 AlgorithmDemo[33588:14525427] str1 = 0x1029045f0 class = __NSCFString str2 = 0x102904640 class = __NSCFString str3 = 0x102904760 class = __NSCFString
由打印可得
- 非集合类可变对象copy是深拷贝
- 非集合类可变对象mutableCopy是深拷贝
- copy和mutableCopy返回的对象都是可变对象
3. 集合类对象
集合类不可变对象
NSString *str1 = @"hello world"; NSMutableString *str2 = [NSMutableString stringWithString:@"hello world"]; NSArray *array1 = [NSArray arrayWithObjects: str1, str2, nil]; NSArray *array2 = [array1 copy]; NSArray *array3 = [array1 mutableCopy]; NSLog(@"\n array1 = %p class = %@ \n", array1, [array1 class]); NSLog(@"\n array2 = %p class = %@ \n", array2, [array2 class]); NSLog(@"\n array3 = %p class = %@ \n", array3, [array3 class]); NSLog(@"\n\n======== 元素是String ======== "); NSLog(@"\n obj0 = %p class = %@ \n", array1[0], [array1[0] class]); NSLog(@"\n obj0 = %p class = %@ \n", array2[0], [array2[0] class]); NSLog(@"\n obj0 = %p class = %@ \n", array3[0], [array3[0] class]); NSLog(@"\n\n======== 元素是mutableString ========"); NSLog(@"\n obj1 = %p class = %@ \n", array1[1], [array1[1] class]); NSLog(@"\n obj1 = %p class = %@ \n", array2[1], [array2[1] class]); NSLog(@"\n obj1 = %p class = %@ \n", array3[1], [array3[1] class]);
输出
2021-05-08 17:34:32.740896+0800 AlgorithmDemo[39309:14557776] array1 = 0x102904180 class = __NSArrayI array2 = 0x102904180 class = __NSArrayI array3 = 0x102904260 class = __NSArrayM ======== 元素是String ======== obj0 = 0x100008220 class = __NSCFConstantString obj0 = 0x100008220 class = __NSCFConstantString obj0 = 0x100008220 class = __NSCFConstantString ======== 元素是mutableString ======== obj1 = 0x1028719b0 class = __NSCFString obj1 = 0x1028719b0 class = __NSCFString obj1 = 0x1028719b0 class = __NSCFString
由打印可得：
- 集合类不可变对象的copy为浅拷贝
- mutableCopy为深拷贝
- 无论copy还是mutableCopy集合内元素都是浅拷贝
集合类可变对象
NSString *str1 = @"hello world"; NSMutableString *str2 = [NSMutableString stringWithString:@"hello world"]; NSMutableArray *array1 = [NSMutableArray arrayWithObjects: str1, str2, nil]; NSMutableArray *array2 = [array1 copy]; NSMutableArray *array3 = [array1 mutableCopy]; NSLog(@"\n array1 = %p class = %@ \n", array1, [array1 class]); NSLog(@"\n array2 = %p class = %@ \n", array2, [array2 class]); NSLog(@"\n array3 = %p class = %@ \n", array3, [array3 class]); NSLog(@"\n\n======== 元素是mutableString ========"); NSLog(@"\n obj0 = %p class = %@ \n", array1[0], [array1[0] class]); NSLog(@"\n obj0 = %p class = %@ \n", array2[0], [array2[0] class]); NSLog(@"\n obj0 = %p class = %@ \n", array3[0], [array3[0] class]); NSLog(@"\n\n======== 元素是String ======== "); NSLog(@"\n obj1 = %p class = %@ \n", array1[1], [array1[1] class]); NSLog(@"\n obj1 = %p class = %@ \n", array2[1], [array2[1] class]); NSLog(@"\n obj1 = %p class = %@ \n", array3[1], [array3[1] class]);
输出:
2021-05-08 17:40:01.757406+0800 AlgorithmDemo[40202:14563979] array1 = 0x1006046e0 class = __NSArrayM array2 = 0x100604860 class = __NSArrayI array3 = 0x100604890 class = __NSArrayM ======== 元素是mutableString ======== obj0 = 0x100008220 class = __NSCFConstantString obj0 = 0x100008220 class = __NSCFConstantString obj0 = 0x100008220 class = __NSCFConstantString ======== 元素是String ======== obj1 = 0x100604510 class = __NSCFString obj1 = 0x100604510 class = __NSCFString obj1 = 0x100604510 class = __NSCFString
结论:
集合类可变对象的mutableCopy和copy都是深拷贝，但集合内元素是浅拷贝
总结
列个表看看
非集合类
| _ | copy | mutableCopy |
| NSString | 浅拷贝返回原对象 |
深拷贝返回新的NSString |
| NSMutableString | 深拷贝返回新NSMutableString |
深拷贝返回新NSMutableString |
一句话总结:非集合类对象只有不可变对象的copy是浅拷贝,其它都是深拷贝
集合类
| _ | copy | mutableCopy |
| NSArray | 浅拷贝元素浅拷贝 |
深拷贝元素浅拷贝 |
| NSMutableArray | 深拷贝元素浅拷贝 |
深拷贝元素浅拷贝 |
一句话总结：集合类对象只有不可变对象的copy是浅拷贝，其它都是深拷贝，且集合内元素都是浅拷贝
也可换个方式总结：
- copy：对不可变对象是浅拷贝，可变对象是深拷贝
- mutableCopy：始终是深拷贝
- 无论深浅拷贝，集合对象内元素都是浅拷贝
