copy 与mutableCopy

很多人都有这样的误会：copy== 浅拷贝？ mutableCopy == 深拷贝
NO！ NO！ NO！
是深拷贝还是浅拷贝不能仅仅根据copy和mutableCopy来判断，还要看被拷贝的对象

对象

对象	类	遵守协议
不可变对象	`NSString` `NSArray` `NSSet` `NSDictionary` `NSAttributedString`	`NSCopying` `NSMutableCopying`
可变对象	`NSMutableString` `NSMutableString` `NSMutableSet` `NSMutableDictionary` `NSMutableAttributedString`	`NSCopying` `NSMutableCopying`
标量对象	`NSNumber` `NSValue`	`NSCopying`

操作

操作	不可变对象(NS*)	可变的对象(NSMutable*)	标量对象
copy	浅拷贝	深拷贝	同assign
mutableCopy	深拷贝	深拷贝	cash

拷贝

名称	描述	占用内存	旧对象引用计数	拷贝后的对象	对象中包含的对象
浅拷贝	拷贝指针	不会改变	+1	为不可变对象	地址不变
深拷贝	拷贝对象	*2	+0	为可变对象	地址不变
赋值(=)	拷贝指针	不会改变	+1	和原对象保持一致	地址不变

代码

NSLog(@"NSArray");
    RCTest * test = [[RCTest alloc] init];
    NSArray * arr = [NSArray arrayWithObject:test];
    NSLog(@"init :%p,%@",arr,arr);
    id arrE = arr;
    NSLog(@"equal :%@:%p,%@",[arrE class],arrE,arrE);
    id arrCopy = [arr copy];
    NSLog(@"copy :%@:%p,%@",[arrCopy class],arrCopy,arrCopy);
    id  arrMutableCopy = [arr mutableCopy];
    NSLog(@"mutableCopy:%@:%p,%@",[arrMutableCopy class],arrMutableCopy,arrMutableCopy);
    
    NSLog(@"NSMutableArray");
    RCTest * test1 = [[RCTest alloc] init];
    NSMutableArray * marr = [NSMutableArray arrayWithObject:test1];
    NSLog(@"init :%p,%@",marr,marr);
    id marrE = marr;
    NSLog(@"equal :%@:%p,%@",[marrE class],marrE,marrE);
    id  marrCopy = [marr copy];
    NSLog(@"copy :%@:%p,%@",[marrCopy class],marrCopy,marrCopy);
    id  marrMutableCopy = [marr mutableCopy];
    NSLog(@"mutableCopy:%@:%p,%@",[marrMutableCopy class],marrMutableCopy,marrMutableCopy);
    
    NSLog(@"NSNumber");
    NSNumber * number = [NSNumber numberWithBool:YES];
    NSLog(@"init :%p,%@,%@",number,number,[number valueForKey:@"retainCount"]);
    id numberCopy = [number copy];
    NSLog(@"copy :%p,%@,%@ - %@",numberCopy,numberCopy,[number valueForKey:@"retainCount"],[numberCopy valueForKey:@"retainCount"]);
    id numberMutableCopy = [number mutableCopy];
    NSLog(@"copy :%p,%@,%@ - %@",numberMutableCopy,numberMutableCopy,[number valueForKey:@"retainCount"],[numberMutableCopy valueForKey:@"retainCount"]);

日志

2018-12-01 18:07:56.838444+0800 TestApp[3527:165370] NSArray
2018-12-01 18:07:56.839175+0800 TestApp[3527:165370] init :0x600000017440,(
    "<RCTest: 0x6000000171f0>"
)
2018-12-01 18:07:56.839629+0800 TestApp[3527:165370] equal :__NSSingleObjectArrayI:0x600000017440,(
    "<RCTest: 0x6000000171f0>"
)
2018-12-01 18:07:56.840314+0800 TestApp[3527:165370] copy :__NSSingleObjectArrayI:0x600000017440,(
    "<RCTest: 0x6000000171f0>"
)
2018-12-01 18:07:56.840764+0800 TestApp[3527:165370] mutableCopy:__NSArrayM:0x6040000504a0,(
    "<RCTest: 0x6000000171f0>"
)
2018-12-01 18:07:56.841474+0800 TestApp[3527:165370] NSMutableArray
2018-12-01 18:07:56.841731+0800 TestApp[3527:165370] init :0x60000025c350,(
    "<RCTest: 0x600000017540>"
)
2018-12-01 18:07:56.841941+0800 TestApp[3527:165370] equal :__NSArrayM:0x60000025c350,(
    "<RCTest: 0x600000017540>"
)
2018-12-01 18:07:56.842167+0800 TestApp[3527:165370] copy :__NSSingleObjectArrayI:0x600000017580,(
    "<RCTest: 0x600000017540>"
)
2018-12-01 18:07:56.842431+0800 TestApp[3527:165370] mutableCopy:__NSArrayM:0x60000025c4d0,(
    "<RCTest: 0x600000017540>"
)
2018-12-01 18:07:56.842616+0800 TestApp[3527:165370] NSNumber
2018-12-01 18:07:56.842882+0800 TestApp[3527:165370] init :0x109062390,1,1152921504606846975
2018-12-01 18:07:56.843076+0800 TestApp[3527:165370] copy :0x109062390,1,1152921504606846975 - 1152921504606846975
2018-12-01 18:07:56.843364+0800 TestApp[3527:165370] -[__NSCFBoolean mutableCopyWithZone:]: unrecognized selector sent to instance 0x109062390
2018-12-01 18:07:57.124815+0800 TestApp[3527:165370] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFBoolean mutableCopyWithZone:]: unrecognized selector sent to instance 0x109062390'
*** First throw call stack: