copy特性，傳入(賦值)不可變對(duì)象時(shí)是淺拷貝:

例如，當(dāng)name屬性為copy特質(zhì)時(shí)，str_1賦值操作時(shí)淺拷貝

test copy

對(duì)象地址沒有變

傳入可變字符串時(shí)是深拷貝:

##用在可變字符串時(shí)是深拷貝:##
//屬性是iOS管理變量數(shù)據(jù)存取的方法
@property (nonatomic, strong) NSString *name;

@property (nonatomic, copy) NSString *meng;

@end

@implementation ViewController

-(void)viewDidLoad {
    [super viewDidLoad];
    [self testCopyAndStrong];
    //[self testString];
}

-(void)testCopyAndStrong {
    
    NSMutableString *str = [[NSMutableString alloc] initWithString:@"meng"];
    
    self.meng = str;
    
    self.name = str;
    
    [str appendString:@"zhiqi"];
    
    
    //實(shí)際上不可變字符串能拼接是因?yàn)樗皇怯迷撟址母北緛砥唇?    NSString *str1 = [str1 stringByAppendingString:@"mmm"];
    
    //&打印指針的地址，沒有&則是打印指針?biāo)赶驅(qū)ο蟮牡刂?    NSLog(@"%p, %p", str, &str);
    
    //strong特性，指針地址不同，但是指針?biāo)赶驅(qū)ο蟮牡刂废嗤?，是淺拷貝(地址拷貝)
    NSLog(@"%p, %p", self.name, &_name);
    
    //copy特性，指針地址不同，指針?biāo)赶虻膶?duì)象的地址也不同，是深拷貝(內(nèi)容拷貝)
    NSLog(@"%p, %p", self.meng, &_meng);
    
    NSLog(@"%@", str);
    //self.name打印出mengzhiqi，可見strong特性只是把指針?biāo)赶驅(qū)ο蟮牡刂房截惲?    NSLog(@"%@", self.name);
    NSLog(@"%@", self.meng);
}

-(void)testString {
    
    NSString *str = @"meng";
    self.meng = str;
    self.name = str;
    
    //&打印指針的地址，沒有&則是打印指針?biāo)赶驅(qū)ο蟮牡刂?    NSLog(@"%p, %p", str, &str);
    
    NSLog(@"%p, %p", self.name, &_name);
    
    NSLog(@"%p, %p", self.meng, &_meng);
}