There is no visible ivar for property named "image"?

Question

Suppose dummy VC has a private property "image"

dummyVC.h

@interface dummyVC : UIViewController
@end

dummyVC.m

@interface dummyVC ()
@property (nonatomic, strong) UIImage *image;
@end


- (void)setImage:(UIImage *)image
{
    if(!_image) { // compiler tells me _image is a 'undeclared indentifier'
        //do something
    }
}

If I try to use _image in its setter, the compiler tells me I am using undeclared identifier.

However, if I change the property name to image1 or anotherImage. There is no problem using _image1 and _anotherImage.

Can anybody explain why this happened?

You're adding a property to the `UIViewController` class itself, in a category? Or you're creating a subclass? — jscs, Mar 02 '14 at 01:53
sorry for the confusion, it is a subclass of `UIViewController`. — David Liu, Mar 02 '14 at 02:38
Can you post a [sample that demonstrates the problem](http://stackoverflow.com/help/mcve)? — jscs, Mar 02 '14 at 02:40

score 1 · Accepted Answer · answered Mar 02 '14 at 03:44

1

I'm going to guess that the problem is either

You are saying
```
@synthesize image;
```
without telling us about it, or
you are supplying a getter method image without telling us about it.

When you say do either of those things and you supply a setter as you are doing here (setImage:), then the synthesized instance variable is named image, not _image. But if you do not supply both a setter and a getter, or you do not say @synthesize, the synthesized instance variable is named _image.

I'm betting that this is the difference between your cases.

answered Mar 02 '14 at 03:44

matt

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Ah, forgot about I supplied a getter for image after a all-day long programming. Thanks! – David Liu Mar 02 '14 at 03:58
2

But you learned the wrong lesson. The lesson is, show your code. Your real code. – matt Mar 02 '14 at 04:07
Or at least code that actually demonstrates the problem. – jscs Mar 02 '14 at 05:15
@JoshCaswell I agree with you, I should post the code at first place. – David Liu Mar 02 '14 at 19:07

There is no visible ivar for property named "image"?

1 Answers1