How do I synthesize Objective-C string?

Question

I am trying to synthesize two strings in Objective C so the setter/getter is automatically created.

In my implementation:

#import "Song.h"

@implementation Song

@synthesize song, track;

@end

In my interface:

#import <Foundation/Foundation.h>

@interface Song : NSObject

@property string song, track;

@end

The error I am getting in my interface file is "Unknown type name string".

The error I am getting in my implementation file is "Expected a property name in @synthesize".

I am unsure what to do because I did this for int and it works.

Given your apparent newness to Objective-C, may I suggest you take some time to work with some good Objective-C tutorials or a good book. Learn the basics first. It will save you a lot of time later. — rmaddy, Feb 20 '14 at 17:04
[Good resources for learning ObjC](http://stackoverflow.com/q/1374660) — jscs, Feb 20 '14 at 19:47

score 5 · Answer 1 · edited May 23 '17 at 12:21

5

There are several problems in your code:

Cocoa does not have a type called string, you need to use NSString instead
As of Xcode 4.4 you do not need to use @synthesize.

Here is how:

@interface Song : NSObject
// Below I am using copy to avoid referencing potentially mutable strings.
// You may or may not want to use this approach.
@property (nonatomic, copy) NSString *song;
@property (nonatomic, copy) NSString *track;

@end

edited May 23 '17 at 12:21

Community

1
1

answered Feb 20 '14 at 16:56

Sergey Kalinichenko

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@matsoftware you don't need either. `strong`, `readwrite` and `atomic` are the default. – Pranav Feb 20 '14 at 17:01

JuJoDi · Answer 2 · 2014-02-20T17:30:52.863

Synthesizing is done automatically in XCode 4.4 and later.

Your actual issue, though, is the declaration of the string properties.

in your header try

@property (strong, nonatomic) NSString *song;
@property (strong, nonatomic) NSString *track;

You can then reference those properties using

self.song

or access the property directly using

_song

Please note the second method is NOT recommended unless you're accessing the instance of the property within the setter or getter

The reason why it worked for int is because int is a primitive (and objective-c is a superset of C). An NSString is an NSObject in Objective-C and you must hold a strong or weak reference to it (you must point to it). You can read Apple's reference on encapsulating data for more information on properties.

score 0 · Answer 3 · answered Feb 20 '14 at 16:56

0

@property(nonatomic,strong) NSString *song;
@property(nonatomic,strong) NSString *track;

answered Feb 20 '14 at 16:56

Abhineet Prasad

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NSString properties (or any of the classes with mutable/immutable types) should really use `copy` instead of `strong`. – Abizern Mar 07 '14 at 14:29

score 0 · Answer 4 · answered Feb 20 '14 at 17:23

In implementation:

#import "Song.h"

@implementation Song

@synthesize song, track;

@end

In interface:

#import <Foundation/Foundation.h>

@interface Song : NSObject

@property (nonatomic, strong)NSString *song;
@property (nonatomic, strong)NSString *track;

@end

How do I synthesize Objective-C string?

4 Answers4