Cocoa and Objective-C: Up and Running by Scott Stevenson

Author:Scott Stevenson
Language: eng
Format: mobi, epub, pdf
Tags: COMPUTERS / Programming / Apple Programming
Publisher: O'Reilly Media
Published: 2010-04-15T16:00:00+00:00

Figure 8-5. A control sending an action message to a target

Setting an action for a button is, literally, telling it which method to call when it’s clicked. It’s the Cocoa equivalent of “Call me at this number when you hear anything.” When that method is called, you can react by running other code in your app to actually perform the task the user is requesting.

Buttons

Buttons are a convenient starting place for learning about actions, because the flow is very easy to understand. The user clicks on the button and the action is sent to another object, called the target. There are more complex buttons with toggle states and other variations, but the most common version is the standard push button.

Almost all push buttons are instances of the NSButton class,[7] which inherits from NSControl. Although there are many built-in visual styles for buttons in AppKit, most of them are not subclasses. Instead, the visual styles are defined through properties on the base NSButton class. All of the items in Figure 8-6 are stock NSButton instances with different styles applied.

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