先说结论

• 可变对象的copy和mutableCopy都是深拷贝，mutableCopy是单层深拷贝
• 不可变对象的copy是浅拷贝，mutableCopy是深拷贝
• copy出来的是不可变对象，mutableCopy出来的是可变对象
• 如果需要容器类完全深拷贝，容器内元素需要实现NSCopying和NSMutableCopying协议，并且使用带有copyItems的方法

测试

不可变对象

- (void)testInmutable{
    NSLog(@"================================");
    NSLog(@"         不可变对象测试");
    NSLog(@"================================\n");
    Person *obj = [[Person alloc]init];
    NSArray *array = [NSArray arrayWithObject:obj];
    NSMutableArray *mutableArray = [array mutableCopy];
    NSArray *copyArray = [array copy];
    NSLog(@"-------------容器类-------------");
    NSLog(@"array:          %p-%@ class:%@",array,array,NSStringFromClass([array class]));
    NSLog(@"copyArray:      %p-%@ class:%@",copyArray,copyArray,NSStringFromClass([copyArray class]));
    NSLog(@"mutableArray:   %p-%@ class:%@\n",mutableArray,mutableArray,NSStringFromClass([mutableArray class]));
    NSString *str = @"123";
    NSString *copyStr = [str copy];
    NSString *mutableStr = [str mutableCopy];
    NSLog(@"-------------非容器类-------------");
    NSLog(@"str:        %p---%@ class:%@",str,str,NSStringFromClass([str class]));
    NSLog(@"copyStr:    %p---%@ class:%@",copyStr,copyStr,NSStringFromClass([copyStr class]));
    NSLog(@"mutableStr: %p---%@ class:%@\n",mutableStr,mutableStr,NSStringFromClass([mutableStr class]));
}

打印结果

可变对象

- (void)testMutable{
    NSLog(@"================================");
    NSLog(@"         可变对象测试");
    NSLog(@"================================\n");
    Person *obj= [[Person alloc]init];
    obj.mName = @"name";
    NSMutableArray *array = [NSMutableArray arrayWithObject:obj];
    NSArray *copyArray = [array copy];
    NSMutableArray *mutableArray = [array mutableCopy];
    NSMutableArray *mutableArray1 = [NSMutableArray arrayWithArray:array];
    NSMutableArray *mutableArray2 = [[NSMutableArray alloc]initWithArray:array copyItems:YES];
    obj.mName = @"newName";
    NSLog(@"-------------容器类-------------");
    NSLog(@"array:          %p-%@ class:%@ name:%@",array,array,NSStringFromClass([array class]),((Person *)[array firstObject]).mName);
    NSLog(@"copyArray:      %p-%@ class:%@ name:%@",copyArray,copyArray,NSStringFromClass([copyArray class]),((Person *)[copyArray firstObject]).mName);
    NSLog(@"mutableArray:   %p-%@ class:%@ name:%@",mutableArray,mutableArray,NSStringFromClass([mutableArray class]),((Person *)[mutableArray firstObject]).mName);
    NSLog(@"mutableArray1:  %p-%@ class:%@ name:%@",mutableArray1,mutableArray1,NSStringFromClass([mutableArray1 class]),((Person *)[mutableArray1 firstObject]).mName);
    NSLog(@"mutableArray2:  %p-%@ class:%@ name:%@\n",mutableArray2,mutableArray2,NSStringFromClass([mutableArray2 class]),((Person *)[mutableArray2 firstObject]).mName);
    NSMutableString *str = [NSMutableString stringWithString:@"123"];
    NSString *copyStr = [str copy];
    NSString *mutableStr = [str mutableCopy];
    NSLog(@"-------------非容器类-------------");
    NSLog(@"str:        %p---%@ class:%@",str,str,NSStringFromClass([str class]));
    NSLog(@"copyStr:    %p---%@ class:%@",copyStr,copyStr,NSStringFromClass([copyStr class]));
    NSLog(@"mutableStr: %p---%@ class:%@\n",mutableStr,mutableStr,NSStringFromClass([mutableStr class]));
}

打印结果

开发时需要注意的

• NSString,NSArray,NSDictionary类型的属性需要用copy修饰
  • 因为如果从mutable对象赋值后，copy会深拷贝mutable对象，并且变成不可变类型，这样在mutable对象再有增删操作时不会对copy修饰的属性造成影响，如果是strong修饰的属性就会跟着改变了。但是容器类因为是单层深拷贝，所以如果对元素的某个属性进行修改，copy后的对象也会被修改