Question

Working on a tutorial with a NSSlider.

What I want: Moving the slider will show slider value in NSTextField.

Tutorial explains that following method will show slider value in text field:

- (IBAction)sliderDidMove:(id)sender {
    NSSlider *slider = sender;
    double value = [slider doubleValue];
    [sliderValueLabel setDoubleValue:value];    
}

Method does not work so I tried to find the method declaration on Apples developer website
but couldn’t find it. From my understanding is the method: sliderDidMove a class method
from the class NSSlider so why I’m unable to find any documentation?

Answer 1

When slider value changes, it sends -[NSControl action] to its -[NSControl target]. So in Interface Builder you need to Ctrl-drag from the slider to the object that has sliderDidMove: (that will probably be either App Delegate or File’s Owner). The name is chosen by the tutorial’s author, it can be anything else.

Alternatively, you can set it up programmatically:

[slider setTarget:self]; // assume the handler is [self sliderDidMove:]
[slider setAction:@selector(sliderDidMove:)];

Note also that this particular task is better solved with bindings: bind both slider’s and label’s value to a double property of some object, and Cocoa will keep them synchronized.