1.当strong与copy用在NSArray对于对象来说没有太大的区别
@interface ViewController () @property (nonatomic, strong) NSArray *arrayS; @property (nonatomic, copy) NSArray *arrayC; @property (nonatomic, strong) NSMutableArray *arrayMS; @property (nonatomic, strong) NSString *str; @end @implementation ViewController - (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. NSArray *a = [[NSArray alloc] initWithObjects:@"hello", nil]; self.arrayC = a; self.arrayS = a; NSLog(@"数组a ---%p -- %@", a,a); NSLog(@"arraryC ---%p -- %@", self.arrayC,self.arrayC); NSLog(@"arraryS ---%p -- %@", self.arrayS,self.arrayS); }
结果：
2016-08-15 16:28:18.571 copydemo[64461:12400898] 数组a ---0x7fe140518c10 -- ( hello ) 2016-08-15 16:28:18.571 copydemo[64461:12400898] arraryC ---0x7fe140518c10 -- ( hello ) 2016-08-15 16:28:18.571 copydemo[64461:12400898] arraryS ---0x7fe140518c10 -- ( hello )由结果可知都是指向同一个对象地址a，此刻a的retainCount＝3
2.在指向NSMutableArray
@interface ViewController () @property (nonatomic, strong) NSArray *arrayS; @property (nonatomic, copy) NSArray *arrayC; @property (nonatomic, strong) NSMutableArray *arrayMS; @property (nonatomic, strong) NSString *str; @end @implementation ViewController - (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. NSMutableArray *a = [[NSMutableArray alloc] initWithObjects:@"hello", nil]; self.arrayC = a; self.arrayS = a; NSLog(@"数组a ---%p -- %@", a, a); NSLog(@"arraryC ---%p -- %@", self.arrayC,self.arrayC); NSLog(@"arraryS ---%p -- %@", self.arrayS,self.arrayS); [a addObject:@"world"]; NSLog(@"数组a ---%p -- %@", a, a); NSLog(@"arraryC ---%p -- %@", self.arrayC,self.arrayC); //copy 深复制， a变化不会影响arrayC
执行结果：
2016-08-15 16:31:35.410 copydemo[64478:12421035] 数组a ---0x7feda1619fc0 -- ( hello ) 2016-08-15 16:31:35.410 copydemo[64478:12421035] arraryC ---0x7feda161ab60 -- ( hello ) 2016-08-15 16:31:35.410 copydemo[64478:12421035] arraryS ---0x7feda1619fc0 -- ( hello ) 2016-08-15 16:31:35.410 copydemo[64478:12421035] 数组a ---0x7feda1619fc0 -- ( hello, world ) 2016-08-15 16:31:35.410 copydemo[64478:12421035] arraryC ---0x7feda161ab60 -- ( hello ) 2016-08-15 16:31:35.410 copydemo[64478:12421035] arraryS ---0x7feda1619fc0 -- ( hello, world )
有结果可知：
copy是进行了一次深复制对这次引用，而strong还是指向原来的对象浅复制
3.对于 ［a copy］［a mutableCopy］区别
如果a是NSArray 则［a copy］是浅复制，［a mutableCopy］是深复制
如果a是NSMutableArray 则［a copy］［a mutableCopy］都是深复制
