將一個NSString複製到另一個

Question

如何將一個NSString複製到另一個NSString？

@interface MyData : NSObject 
{ 
    @private 

    //user's private info 
    NSInteger uID; 
    NSString *name; 
    NSString *surname; 
    NSString *email; 
    NSString *telephone; 

    //user's picture 
    UIImage *image; 
} 

@property (nonatomic, assign) int uID; 
@property (nonatomic, retain) NSString *name; 
@property (nonatomic, retain) NSString *surname; 
@property (nonatomic, retain) NSString *email; 
@property (nonatomic, retain) NSString *telephone; 
@property (nonatomic, retain) UIImage *image; 
@end 

我有這種類型的兩個對象。 MyData * obj1，obj2;

首先被初始化。其次，我想先初始化。

obj2 = [obj1 copy]; //crashes 

    newData.surname = data.surname; //crashes to 
    newData.email = data.email; 
    newData.telephone = data.telephone; 

我neeeeed的第二個對象不保留一個COPY！請幫助！感謝名單！

Answer 1

你的對象也許應該實現自身拷貝：

@implementation MyData 

-(id)copyWithZone:(NSZone *)zone 
{ 
    MyData *obj = [[[self class] alloc] init]; 
    obj.uID = self.uId; 
    obj.name = self.name 
    ... 
    return obj; 
} 

.... 
@end 

Answer 2

可以使用的NSString方法stringWithString。

請參閱also stringwithstring, what's the point?瞭解何時可能會優先考慮簡單地給它一個相同的字符串。

Answer 3

更改@財產的使用副本，而不是保留：

@property (nonatomic) int uID; 
@property (nonatomic, copy) NSString *name; 
@property (nonatomic, copy) NSString *surname; 
@property (nonatomic, copy) NSString *email; 
@property (nonatomic, copy) NSString *telephone; 
@property (nonatomic, copy) UIImage *image; 

請注意，您也不必爲UID的分配。只要把那部分放開。然後你可以很容易地通過alloc創建一個副本，並啓動第二個MyData對象並分配屬性：

MyData data = [[MyData alloc] init]; 
newData.surname = data.surname; 
newData.email = data.email; 
newData.telephone = data.telephone;