View's dataSource property set to nil after I set it - objective-c

Question

New to iOS/Objective-C here. I've spent a lot of time trying to figure this out, but just can't manage it. Here's what's happening:
Click a 'Graph' button on my RootViewController's view
GraphViewController takes over, has a graphView property
I set the graphView's dataSource property to self
Checking self.graphView.dataSource with NSLog confirms that it does indeed point to self
When GraphView's drawRect: is called, self.dataSource is set to (null), where I expected it to point to the GraphViewController object
To summarise: I'm instantiating the graphView property in the view controller, then setting its dataSource, but by the time the view's drawRect: is called the dataSource is no longer set.
GraphViewController.m:
#import "GraphViewController.h"
#import "GraphView.h"
#implementation GraphViewController
#synthesize graphView = _graphView;
#synthesize program = _program;
- (GraphView *)graphView {
if(!_graphView) {
_graphView = [[GraphView alloc] init];
[_graphView setDataSource:(id)self];
}
return _graphView;
}
#end
GraphViewController.h:
#import <UIKit/UIKit.h>
#import "GraphView.h"
#interface GraphViewController : UIViewController
#property (strong, nonatomic) IBOutlet GraphView *graphView;
#end
GraphView.m:
#import "GraphView.h"
#implementation GraphView
#synthesize dataSource = _dataSource;
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
// Initialization code
NSLog(#"initWithFrame called, self.dataSource=%#", self.dataSource);
}
return self;
}
- (void)drawRect:(CGRect)rect
{
NSLog(#"drawRect:");
NSLog(#"\tself=%#", self);
NSLog(#"\tself.dataSource=%#", self.dataSource); // is (null), shouldn't be
[self.dataSource programToGraph];
}
#end
GraphView.h:
#import <UIKit/UIKit.h>
#class GraphView;
#protocol GraphViewDataSource
- (id)programToGraph;
#end
#interface GraphView : UIView
#property (nonatomic, weak) IBOutlet id <GraphViewDataSource> dataSource;
#end

Answer 1

So it looks like the GraphViewController instance is being deallocated, which will nil out the dataSource property.
So you should go back and look at how you are creating and managing that GraphViewController. A common mistake is to create a view controller like that, then borrow its view and throw it into some other view controller's view hierarchy, and then let the original view controller just go away.
I would look at that, and if you don't see it there, post the code where you create and present the GraphViewController.
Oh, and where are you calling initWithFrame: from?? It almost looks like you could also have two different instances of GraphView floating around. Try logging 'self' along with self.datasource to check that also.