關於iOS的深copy和淺copy 以及copy 和 strong 的區別

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之前都是靠記憶來維持copy和strong  也有問過我 。  我自己說起來才感覺都說不很清楚

通過簡單都代碼來驗證一下 。 有時候花點時間驗證一下才能讓思路更加清晰

    NSMutableString * mustr = [NSMutableString stringWithString:@"good"];

    

    self.str = mustr;

    

    self.fuzhiString = mustr;

    

    NSLog(@"self.str is (%@) ==== str,self.fuzhiString is (%@)",self.str,self.fuzhiString);

    

    NSLog(@"self.str *p is (%@) ==== str,self.fuzhiString *p is (%@)",self.str,self.fuzhiString);

 

    注釋:列印結果 == self.str is (good) ==== str,self.fuzhiString is (good)

    self.str *p is (0x600000059350) ==== str,self.fuzhiString *p is (0xa000000646f6f674)

    

    [mustr appendString:@"night"];

    

    NSLog(@"self.str is (%@) ==== str,self.fuzhiString is (%@)",self.str,self.fuzhiString);

    

    NSLog(@"self.str *p is (%@) ==== str,self.fuzhiString *p is (%@)",self.str,self.fuzhiString);

    

    注釋:列印結果 ==self.str is (goodnight) ==== str,self.fuzhiString is (good)

    self.str *p is (0x600000059350) ==== str,self.fuzhiString *p is (0xa000000646f6f674)

 

 

 

   列印結果: copy修飾的屬性為深copy(開闢一個新記憶體指向一個新的值)

                 strong修飾的屬性為淺copy(跟著mustr的值的改變而改變);

   同時表明字串為了防止不經意的修改 應該使用copy,養成好的習慣.

   當然用NSString用copy和strong是沒有什麼區別的

 

 

 

 

關於iOS的深copy和淺copy 以及copy 和 strong 的區別