Adding stuff to UIView from other class - iphone

Question

It's a very simple question, but I don't get it to work properly. I have the following setup:
iPhone app with a main controller (ViewController). I thought it would be better to export some parts of it to new files (better structure etc). So I created a new class, "ClassFile". This is what I want to do:
ViewController.m
// Launch function from other ViewController class
-(void)someWhereAtViewController {
ClassFile *Classinstance = [[ClassFile alloc] init];
UILabel *label = [Classinstance createLabel];
[Classinstance release];
}
ClassFile.m
// Do some stuff
-(UILabel *)createLabel {
// Create an UILabel "label"
[...]
// Now add the label to the main view
// Like this it clearly doesn't work, but how to do it?
[self.view addSubview:label]
// Return the label to the other class
return label
}
Thanks a lot for the input! As far as I know, everything in this dummycode works except adding the label to the main view.

Answer 1

-(UILabel *)createLabelInView: (UIView *)view {
// Create an UILabel "label"
[...]
// Now add the label to the main view
// Like this it clearly doesn't work, but how to do it?
[view addSubview:label]
// Return the label to the other class
return label
}
and then call it with:
// Launch function from other ViewController class
-(void)someWhereAtViewController {
ClassFile *Classinstance = [[ClassFile alloc] init];
UILabel *label = [Classinstance createLabelInView: self.view];
[Classinstance release];
}

Answer 2

It sounds like you want a "Category". A category is a way to add methods to existing classes, regardless of whether you have their source code or not.
So you have:
//ViewController.h
#interface ViewController : UIViewController {
}
#end
//ViewController.m
#import "ViewController.h"
#implementation ViewController
...
#end
You want another file with more methods for ViewController, correct? If so, then you'd do:
//ViewController+Extras.h
#import "ViewController.h"
#interface ViewController (Extras)
- (UILabel *)createLabel;
#end
//ViewController+Extras.m
#import "ViewController+Extras.h"
#implementation ViewController (Extras)
- (UILabel *)createLabel {
return [[[UILabel alloc] initWithFrame:CGRectMake(0,0,42,42)] autorelease];
}
#end
And then you'll be able to do:
//ViewController.m
#import "ViewController.h"
#import "ViewController+Extras.h"
#implementation ViewController
- (void)doStuff {
UILabel *newLabel = [self createLabel];
//do stuff
}
#end
For more information on Categories, check out the Documentation.