How does an NSView subclass communicate with the controller?

Question

I am brand spanking new to Cocoa programming, and am still kind of confused about how things wire together.

I need a pretty simple application that will fire off a singl

Answer 1

First, your view needs a reference to the controller. This can be a simple iVar set at runtime or an outlet (designated by IBOutlet) connected at design time.

Second, NSControl is a subclass of NSView, which provides the target/action mechanism machinery for free. Use that for target/action style controls. This provides a simple way of setting the reference to your controller (the target) and the method to call when fired (the action). Even if you don't use a cell, you can still use target/action easily (NSControl usually just forwards this stuff along to its instance of an NSCell subclass but doesn't have to).

Answer 2

You could either add it as an IBOutlet like Joshua said, or you could use the delegate pattern.

You would create a Protocol that describes your delegate's methods like

@protocol MyViewDelegate
    - (void)doStuff:(NSEvent *)event;
@end

then you'd make your view controller conform to the MyViewDelegate protocol

@interface MyViewController: NSViewController <MyViewDelegate> {
    // your other ivars etc would go here 
}
@end

Then you need to provide the implementation of the doStuff: in the implementation of MyViewController:

- (void)doStuff:(NSEvent *)event
{
    NSLog(@"Do stuff delegate was called");
}

then in your view you'd add a weak property for the delegate. The delegate should be weak, so that a retain loop doesn't form.

@interface MyView: NSView

@property (readwrite, weak) id<MyViewDelegate> delegate;

@end

and then in your view you'd have something like this

- (void)mouseDown:(NSEvent *)event
{
    // Do whatever you need to do

    // Check that the delegate has been set, and this it implements the doStuff: message
    if (delegate && [delegate respondsToSelector:@selector(doStuff:)]) {
        [delegate doStuff:event];
    }
 }

and finally :) whenever your view controller creates the view, you need to set the delegate

 ...
 MyView *view = [viewController view];
 [view setDelegate:viewController];
 ...

Now whenever your view is clicked, the delegate in your view controller should be called.

Answer 3

you can also use a selector calling method, define two properties in custom class:

@property id parent;
@property SEL selector;

set them in view controller:

graph.selector=@selector(onCalcRate:);
graph.parent=self;

and call as:

-(void)mouseDown:(NSEvent *)theEvent {
    [super mouseDown:theEvent];
    [_parent performSelector:_selector withObject:self];
}