呼叫代表方法（iOS）

Question

Fist of all I want to show you my code/storyboard:

This is my storyboard: I have a little UISlider and a UIView. The UIView is a custom view and his class is "SquareView". This is the code:

SquareView.h

#import <UIKit/UIKit.h>

    @class SquareView;

    @protocol SquareViewDelegate <NSObject>

    -(int)giveMeTheNumbersOfSquare:(SquareView *)squareView;

    @end

    @interface SquareView : UIView

    @property (nonatomic , weak) IBOutlet id<SquareViewDelegate> delegate;

    @end

and SquareView.m

#import "SquareView.h"

@implementation SquareView
@synthesize delegate;
- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
    }
    return self;
}
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{

    int numberOfSquare = [delegate giveMeTheNumbersOfSquare:self];
    NSLog(@"Value of numberOfSquare in drawRect---> %d" ,numberOfSquare);
    //numberOfSquare = 20;
    for (int i=0; i<numberOfSquare; i++) {
        float x = arc4random() % (int)self.frame.size.width - 20;
        float y = arc4random() % (int)self.frame.size.width - 20;

        UIRectFill(CGRectMake(x, y, 20.0, 20.0));
       // NSLog(@"X---> %f" ,x);
        //NSLog(@"Y---> %f" ,y);
        [self setNeedsDisplay];
    }

    // Drawing code
}
@end

Now the ViewController... The ViewController is the SquareView's Delegate.

ViewController.h

#import <UIKit/UIKit.h>
#import "SquareView.h"

@interface TestViewController : UIViewController <SquareViewDelegate>

@property (weak) IBOutlet SquareView *squareView;
@property(weak) IBOutlet UISlider *slider;

-(IBAction)changeSquareNumbers:(id)sender;


@end

and ViewController.m

#import "TestViewController.h"

@interface TestViewController ()
{
    int _squareCount;
}

@end

@implementation TestViewController

@synthesize squareView = _squareView;
@synthesize slider = _slider;

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

-(void)awakeFromNib
{
    [_squareView setDelegate:self];
    _squareCount = 50;
    [self.squareView setNeedsDisplay];
}

/********* Delegate Method *********/
-(int)giveMeTheNumbersOfSquare:(SquareView *)squareView
{
    //return _squareCount;
    NSLog(@"Value of _squareCount in giveMeTheNumberOfSquare ---> %d" ,_squareCount);
    return _squareCount;
}

-(IBAction)changeSquareNumbers:(UISlider *)sender
{
    NSLog(@"Value of slider in changeSquareNumbers --> %f" ,[sender value]]);
    _squareCount = (int)[sender value];
    NSLog(@"Value of _sqareCount ---> %d" ,_squareCount);
    [self.squareView setNeedsDisplay];
}

Now... in the SquareView.m file, in the drawRect function I don't know why the program NEVER call the "giveMetheNumbersOfSquare function. The "numberOfSquare" in drawRect stay at 0!!! I don't understand why the program NEVER enter in the "giveMeTheNumberOfSquare" Function!!

Thanks!!

Answer 1

Make sure that the delegate is being set correctly. You might need to alloc or initialize your squareView. Also if you're using a storyboard you might not be calling awakeFromNib .