Question

I’m getting the error on “float pos = [sender value];”…sender should be a UISlider that I set up in Interface Builder.

ButtonViewController.m

- (IBAction)slide: (id)sender {
 float pos = [sender value];
 loadValue.progress = pos;
}

ButtonViewController.h

@interface Button_Fun4ViewController : UIViewController {
 IBOutlet UIProgressView *loadValue;
}

- (IBAction)slide: (id)sender;

THANKS.

Answer 1

While sender “should” be a UISlider, the compiler doesn’t know that. All it sees is id, which it binds to the first matching method signature it can find; probably one that returns something other than a float (and as a final guess, the compiler will assume it returns an id).

You’ll need to typecast this over to UISlider in this case:

- (IBAction)slide: (id)sender {
    float pos = [(UISlider *)sender value];
    loadValue.progress = pos;
}

Using NSAssert() or an if() to double-check that this is fact a UISlider wouldn’t be a bad idea, but isn’t strictly necessary.