Let’s get back to RGBWell and add a control – an NSSlider – to your interface.
A slider allows a user to select a value from some range. In the object library, search for a slider and drag a Horizontal Slider onto the top righthand side of the window (Figure 5.11).
Figure 5.11 Dragging a slider onto the window
Next, find a label in the object library and drag it onto the canvas to the left of the slider and change its text to R. Figure 5.12 shows what the interface should look like at this point.
Figure 5.12 RGBWell with one label and one slider
Cocoa controls tend to be very versatile. ...