copy one NSString to another

Question

How to copy one NSString to another?

@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

I have two objects of this type. MyData *obj1, obj2;

First is initialized. Second I want to initialize with first.

obj2 = [obj1 copy];   //crashes

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

I neeeeed a COPY of second object NOT RETAIN!!! Help please! Thanx!

I want to copy MyData, but I want that fields in different objects will have different addresses. — yozhik, Nov 17 '10 at 16:19

score 5 · Answer 1 · edited May 23 '17 at 11:43

5

you can use the NSString method stringWithString.

See also stringwithstring, what's the point? to understand when this might be preferred to simply giving it the same string.

edited May 23 '17 at 11:43

Community

1
1

answered Nov 17 '10 at 15:51

Alex Brown

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score 4 · Accepted Answer · answered Nov 17 '10 at 15:50

4

your object should probably implement the copy itself:

@implementation MyData

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

....
@end

answered Nov 17 '10 at 15:50

Romain

4,080
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Objects has defferent addresses but!!!! NSString object has EQUAL addresses. I need differrent addresses. – yozhik Nov 17 '10 at 16:07
then you should copy them, using obj.name = [self.name copy] and so on – Romain Nov 17 '10 at 16:15
if you need a different address, you must create it yourself. Allocate your NSzone zone and then use it your copy obj2 = [obj1 copyWithZone:zone], and propagate in the copy method: -(id)copyWithZone:(NSZone *)zone{ ... obj.name = [self.name copyWithZone:zone] ... } – Romain Nov 17 '10 at 16:24
@ Romain previous comment: "obj.name = [self.name copyWithZone:zone]" this is a memory leak – user102008 Feb 22 '11 at 23:01

score 2 · Answer 3 · answered Nov 17 '10 at 15:56

Change your @property's to use copy instead of retain:

@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;

Note that you also don't need the assign for the uID. Just leave that part out. Then you can easily create a copy by alloc and init-ing a second MyData object and assigning the properties :

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

This variant not recommended in my situation. – yozhik Nov 17 '10 at 15:59 — yozhik, Nov 17 '10 at 15:59

copy one NSString to another

3 Answers3