Objective-C can someone explain how to programmatically display a view - objective-c

Question

I'm just not getting this, I want to display a view in my app when a user clicks a button.
I've gotten this far:
NSView* unitMarker = [[NSView alloc] initWithFrame: NSMakeRect( 20.0, 20.0, 80.0, 50.0 ) ];
How would I display this view with a red background?
Thanks

Answer 1

#Aaron: he says he wants to do this programmatically. Also he's using NSView, not UIView, so an iPhone tutorial would be almost irrelevant.
#Mike: Your description of what you want to do is a bit vague. We have a bit of code creating, a view, but no context to tell us exactly what you are trying to do. Do you want the view to come up in a new window or the same? Do you want to replace a view that's already there? We don't even really know your skill level.
I suggest you go check out the documentation for NSView: http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/ApplicationKit/Classes/NSView_Class/Reference/NSView.html

Answer 2

I've gotten this far:
NSView* unitMarker = [[NSView alloc] initWithFrame: NSMakeRect( 20.0, 20.0, 80.0, 50.0 ) ];
How would I display this view with a red background?
You wouldn't, because a plain NSView doesn't draw anything.
First, you need to subclass NSView, implement drawRect: in that subclass to fill its bounds with red, and instantiate that subclass instead of NSView directly.
You should read the View Programming Guide.
How would I display this view …
You wouldn't. The view displays itself when it is appropriate to do so.
It won't ever be appropriate for it to draw itself until you add it to a view hierarchy. Every window has one, rooted at its content view. You need to add this view either to a content view or to some descendant view (subview, subview of a subview, etc.) of a content view.
You normally should not tell a view to display from your controller. That's the window's job. When you do change a property or properties of the view that affect what it draws, set the view as needing display, and let the window tell the view to display when it's appropriate to do that.

Answer 3

Say this out loud 10 times repeatedly:
Interface Builder is my friend.
I was able to put together a sample project doing exactly what you want to do in about 5 minutes by leveraging Interface Builder as part of the process. http://www.markdouma.com/developer/ShowWindowWithRedView.zip.
You can't show a view without placing it in a window first; by far the easiest way to do this kind of a thing is to drag out a second window in Interface Builder, set it to not be visible on launch, drag a generic NSView custom view onto the Window, set its class to be SRRedView (your red view subclass). As d11wtq posted, you override NSView's primitive drawing method like he shows (though personally I prefer NSBezierPath :-P).
In your controller class, you define IBOutlets, and then hook those up in Interface Builder. These provide you with a way to reference the important parts of your interface so that you can manipulate them programmatically.
I added one IBAction method, which the button in the main window is hooked up to call. That method simply tells the second window to show itself.
- (IBAction)showWindowWithRedView:(id)sender {
[windowWithRedView makeKeyAndOrderFront:nil];
}
In the 8 years or more that I've been doing Cocoa programming, I don't think I've ever needed to resort to manually creating windows and views. It has always been much faster to simply load another nib file that contains the windows or views I need to display. Using Interface Builder along with Xcode to create your app is quite a bit different than how other IDEs work. (Specifically, when you arrange stuff in Interface Builder you're not generating code as much as you are creating instances of UI objects and then "freeze-drying" them in their current arrangement into a .nib archive file. When you launch the app, they are brought back to life. Or at least that's the way I think about it).

Answer 4

You need to subclass NSView and implement drawRect:.
In this case you're just going to fill the entire rect with red.
#interface MyView : NSView {
}
#end
#implementation MyView
-(void)drawRect:(NSRect)dirtyRect {
[[NSColor redColor] set];
NSRectFill(dirtyRect);
}
#end
That's an extremely basic example that does what you want, but if you want to do more complex things (adding borders (strokes) or drawing curves (paths) etc), then you need to learn all the drawing classes available to you.
Scott Stevenson has written some easy to follow tutorials on this:
http://cocoadevcentral.com/d/intro_to_quartz/ and;
http://cocoadevcentral.com/d/intro_to_quartz_two/