概念
浅拷贝：指针拷贝，不会创建一个新的对象。浅拷贝简单点说就是对内存地址的复制，让目标对象指针和源对象指针指向同一片内存空间。
深拷贝: 内容拷贝，会创建一个新的对象。深拷贝就是拷贝地址中的内容，让目标对象产生新的内存区域，且将源内存区域中的内容复制到目标内存区域中。
copy：使用copy生成一个不可变副本，无论是对可变对象拷贝还是对不可变对象拷贝。
mutableCopy：使用mutableCopy生成一个可变副本，无论是对可变对象拷贝还是对不可变对象拷贝。
对非集合类对象的copy与mutableCopy：
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
NSString*immutableString =@"origin";
NSLog(@"%p",immutableString);
NSString*copyString = [immutableStringcopy];
NSLog(@"%p",copyString);
NSMutableString*mutableCopyString = [immutableStringmutableCopy];
NSLog(@"%p",mutableCopyString);
NSMutableString *mutableString = [NSMutableString stringWithString:@"origin"];
NSLog(@"%p",mutableString);
NSString*aCopyString = [mutableStringcopy];
NSLog(@"%p",aCopyString);
NSMutableString*aMutableCopyString = [mutableStringmutableCopy];
NSLog(@"%p",aMutableCopyString);
}
输出结果：
2018-11-09 16:03:51.223209+0800 OC-Swift[5527:194392] 0x10ab7c068
2018-11-09 16:03:51.223402+0800 OC-Swift[5527:194392] 0x10ab7c068
2018-11-09 16:03:51.223547+0800 OC-Swift[5527:194392] 0x600000b679f0
2018-11-09 16:03:51.223668+0800 OC-Swift[5527:194392] 0x600000b61440
2018-11-09 16:03:51.223760+0800 OC-Swift[5527:194392] 0xf995fba58d33f6fa
2018-11-09 16:03:51.223864+0800 OC-Swift[5527:194392] 0x600000b61650
可见， 在非集合类对象中，对 immutable（不可变） 对象进行 copy 操作，是指针复制，mutableCopy 操作时内容复制；对 mutable（可变） 对象进行 copy 和 mutableCopy 都是内容复制
对集合类对象的copy与mutableCopy：
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
NSArray*immutableArray = @[@"a",@"b",@"c",@"d"];
NSLog(@"%p",immutableArray);
NSString*copyArray = [immutableArraycopy];
NSLog(@"%p",copyArray);
NSMutableString*mutableCopyArray = [immutableArraymutableCopy];
NSLog(@"%p",mutableCopyArray);
NSMutableArray *mutableArray = [NSMutableArray arrayWithObject:[NSMutableArray arrayWithObject:@"abcd"]];
NSLog(@"%p",mutableArray);
NSArray*aCopyArray = [mutableArraycopy];
NSLog(@"%p",aCopyArray);
NSMutableArray*aMutableCopyArray = [mutableArraymutableCopy];
NSLog(@"%p",aMutableCopyArray);
}
输出结果：
2018-11-09 16:13:13.706506+0800 OC-Swift[5638:198595] 0x600001a3c630
2018-11-09 16:13:15.574032+0800 OC-Swift[5638:198595] 0x600001a3c630
2018-11-09 16:13:16.775059+0800 OC-Swift[5638:198595] 0x600001a3c6f0
2018-11-09 16:13:18.946782+0800 OC-Swift[5638:198595] 0x600001a30ea0
2018-11-09 16:13:23.310313+0800 OC-Swift[5638:198595] 0x60000167afc0
2018-11-09 16:13:25.532082+0800 OC-Swift[5638:198595] 0x600001a3c690
在集合类对象中，对 immutable （不可变）对象进行 copy，是指针复制， mutableCopy 是内容复制；对 mutable（可变） 对象进行 copy 和 mutableCopy 都是内容复制。
但是：
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
NSMutableArray *mutableArray = [NSMutableArray arrayWithObject:[NSMutableArray arrayWithObject:@"abcd"]];
NSArray*aCopyArray = [mutableArraycopy];
NSMutableArray*aMutableCopyArray = [mutableArraymutableCopy];
NSMutableArray*firstArray = mutableArray.firstObject;
[firstArrayaddObject:@"efg"];
NSLog(@"mutableArray = %@\n aCopyArray = %@\n aMutableCopyArray = %@\n",mutableArray,aCopyArray,aMutableCopyArray);
}
输出结果：
2018-11-09 16:19:32.247795+0800 OC-Swift[5700:201553] mutableArray = (
(
abcd, efg
)
)
aCopyArray = (
(
abcd, efg
)
)
aMutableCopyArray = (
(
abcd, efg
)
)
可见，集合对象的内容复制仅限于对象本身，对象元素仍然是指针复制。就是：
[immutableObject copy]// 浅复制
[immutableObject mutableCopy]//单层深复制
[mutableObject copy]//单层深复制
[mutableObject mutableCopy]//单层深复制
后记：
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
NSMutableArray *mutableArray = [NSMutableArray arrayWithObject:[NSMutableArray arrayWithObject:@"abcd"]];
NSMutableArray*aMutableCopyArray = [[NSMutableArray alloc] initWithArray:mutableArray copyItems:YES];
NSMutableArray*firstArray = mutableArray.firstObject;
[firstArray addObject:@"efg"];
NSLog(@"mutableArray = %@\n aMutableCopyArray = %@\n",mutableArray,aMutableCopyArray);
}
输出结果：
2018-11-09 16:36:23.086028+0800 OC-Swift[5879:208849] mutableArray = (
(
abcd, efg
)
)
aMutableCopyArray = (
(
abcd
)
)
可以用NSArray的这个- (instancetype)initWithArray:(NSArray *)array copyItems:(BOOL)flag方法进行深层次的复制。
NSDictionary的这个- (instancetype)initWithDictionary:(NSDictionary *)otherDictionary copyItems:(BOOL)flag方法进行深层次的复制。
NSSet的这个- (instancetype)initWithSet:(NSSet *)set copyItems:(BOOL)flag方法进行深层次的复制。
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