Objective c property issue

Question

In my Settings.h file I have the line

@property (nonatomic, retain) NSArray * connections;

Also in the Settings.m file there are importing:

#import "Settings.h"

and later I provide the implementation

- (NSArray*)connections 
{
    return connections;
}
- (void)setConnections:(NSArray*)_connections
{
    connections = _connections; 
    // do some more stuff
}

But both in getter and setter I get an error about use of undeclared identifier 'connections' I have no idea what do I do wrong, so any of your help would be greatly appreciated!

By the way that is not how the setter for a nonatomic retained property looks! Expect unexpected memory problems. — jrtc27, Feb 13 '12 at 12:46
Do you mean that I have to use `connections = [_connections retain];`? — Solomiya, Feb 13 '12 at 13:16

score 2 · Answer 1 · edited Dec 11 '12 at 08:33

2

in Settings.m 

@synthesize connections = _connections;

in setting.h

edited Dec 11 '12 at 08:33

talha2k

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answered Dec 11 '12 at 08:17

yuquan0821

21
4

Monolo · Accepted Answer · 2012-02-13T14:36:33.253

0

You are, quite correctly, trying to use an ivar (called connections) as a backing store for your property, also called connections;

To get it to work, you should simply declare an ivar like this:

// Settings.h

NSArray * connections;

It should go between the curly brackets of the class declaration, like this:

@interface MyClass : MySuperClass {
    NSArray *connections;
    // More ivars...
}

@property (nonatomic, assign) NSArray *connections;

@end

edited Feb 13 '12 at 14:36

answered Feb 13 '12 at 10:53

Monolo

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Yes, I've already added it and it worked :) Thank you for your help! – Solomiya Feb 13 '12 at 10:57

score -1 · Answer 3 · answered Feb 13 '12 at 10:40

-1

In Settings.h add an instance variable NSArray *connections; (if it's not there already), then in Settings.m just below @implementation add this:

@dynamic connections;

Another option is to remove you accessors and go for @synthesize connections; instead of dynamic and the accessor methods will be created for you.

answered Feb 13 '12 at 10:40

Simon

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yes, it would be reasonable to remove my own accessors, but I have to specify few more actions in setter, which I didn't mention in here. – Solomiya Feb 13 '12 at 10:49
Hmm, when I add `@dynamic connections;` the error doesn't disappear. – Solomiya Feb 13 '12 at 10:53
Oh, no-no, I made a mistake :) Now, everything works great! Thank you very much! – Solomiya Feb 13 '12 at 10:55
What is the need for `@dynamic connections`? – Monolo Feb 13 '12 at 11:02
Hmm, I don't know - I just tried to remove it and nothing changed, everything works like before – Solomiya Feb 13 '12 at 11:53
As I understand it `@dynamic` is needed in order to access `connections` as a property, e.g. in bindings or using `mySetting.connection` notation. From what I've read you use it when you want to write the property accessors yourself. As such, `[mySetting connections]` would work without the `@dynamic`, while `mySetting.connections` would not. I might be wrong on this though. – Simon Feb 13 '12 at 13:10
I thought that `@dynamic` is required if I'm going to define accessors later, e.g. in subclasses. What about notation, in my application I write `currentSettings.connections = [fields objectForKey:@"connections"];` and it works fine – Solomiya Feb 13 '12 at 13:22
Yes, I am obviously wrong here. http://stackoverflow.com/a/4621968/222245 offers a pretty good description of `@dynamic`. – Simon Feb 13 '12 at 13:43
You know, probably you're not - http://stackoverflow.com/questions/4524954/what-is-common-case-for-dynamic-usage/4524983#4524983 :) As I got, it's just a question of your programming style – Solomiya Feb 13 '12 at 15:05

Objective c property issue

3 Answers3