objective-c – Obj-C：委托方法未被调用

GraphViewController.h：

@interface GraphViewController : UIViewController <GraphViewDelegate> {
    GraphView *graphView;
    float scale;
}

@property (retain) IBOutlet GraphView *graphView;
@property float scale;

- (IBAction)zoomIn;
- (IBAction)zoomOut;

@end

GraphViewController.m：

@implementation GraphViewController

@synthesize graphView,scale;

- (NSString *)functionForGraph:(GraphView *)requestor {
    NSLog(@"%@",@"culo peluo");
    return @"lol";
}

- (float)scaleForGraph:(GraphView *)requestor {
    return self.scale;
}

- (IBAction)zoomIn {

}

- (IBAction)zoomOut {

}

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {

    }
    return self;
}

- (void)dealloc
{
    [super dealloc];
}

- (void)didReceiveMemoryWarning
{
    // Releases the view if it doesn't have a superview.
    [super didReceiveMemoryWarning];

    // Release any cached data,images,etc that aren't in use.
}

#pragma mark - View lifecycle

- (void)viewDidLoad
{
    [super viewDidLoad];
    self.graphView.delegate = self;
    self.scale = 20;
    [self.graphView setNeedsDisplay];
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    // Return YES for supported orientations
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

@end

GraphView.h：

@class GraphView;

@protocol GraphViewDelegate 
- (NSString *)functionForGraph:(GraphView *)requestor;
- (float)scaleForGraph:(GraphView *)requestor;
@end

@interface GraphView : UIView {
    id <GraphViewDelegate> delegate;
}

@property (assign) id <GraphViewDelegate> delegate;

@end

GraphView.m：

@implementation GraphView

@synthesize delegate;

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
    }
    return self;
}

- (void)drawRect:(CGRect)rect
{
    CGFloat cgScale = [self.delegate scaleForGraph:self];
    [AxesDrawer drawAxesInRect:self.bounds originAtPoint:self.center scale:cgScale]; 
}


- (void)dealloc
{
    [super dealloc];
}

@end