Question

我正在构建一个图形应用程序，我有一个视图和一个视图控制器，它充当视图的委托（检索信息）。虽然我还没有开始实际绘图，但我目前正在尝试将值存储在字典中;但是，我在视图控制器中有条理地放置了某些NSLog，我注意到我从视图调用的委托方法根本没有被调用。例如，我调用scaleForGraph函数，但它不执行。对此我不熟悉，我不确定是否有我遗漏的东西。仅供参考：我没有错误，它编译并执行。我试图尽可能减少代码。谢谢你的帮助！

这是我的观点的.h，我定义了协议：

//  GraphView.h

#import <UIKit/UIKit.h>

@class GraphView;

@protocol GraphViewDelegate <NSObject>
- (float)scaleForGraph:(GraphView *)requestor;
-(NSMutableDictionary*) valuesForGraph:(GraphView *)requestor withWidth:(float) width;

@end

@interface GraphView : UIView
@property (nonatomic) id <GraphViewDelegate> delegate;
@property (nonatomic) id expressionCopy;

@end

这是.m：

#import "GraphView.h"

@implementation GraphView
@synthesize expressionCopy = _expressionCopy;

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

- (void)awakeFromNib
{
    self.contentMode = UIViewContentModeRedraw;
}

// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
    CGContextRef c = UIGraphicsGetCurrentContext();
    CGRect screenBound = [[UIScreen mainScreen] bounds];
    CGSize screenSize = screenBound.size;
    CGFloat width = screenSize.width;
    CGFloat height = screenSize.height;
    float scale = [self.delegate scaleForGraph:self];
    NSLog([NSString stringWithFormat:@"My Scale: %f",scale]); //always returns 0
    NSMutableDictionary *graphValues = [self.delegate valuesForGraph:self withWidth:width];
}
@end

这是我的视图控制器.h：

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

@interface GraphingViewController : UIViewController <GraphViewDelegate>
@property (weak, nonatomic) IBOutlet GraphView *graphView;
@property (strong, nonatomic) IBOutlet UIStepper *stepper;
- (IBAction) changedScale:(UIStepper *)stepper;
@property (nonatomic) int scale;
@property (nonatomic) id expressionCopy;
@end

这是控制器的.m：

#import "GraphingViewController.h"
@interface GraphingViewController ()

@end

@implementation GraphingViewController
@synthesize expressionCopy = _expressionCopy;

- (void)updateUI
{
    self.stepper.value = self.scale;
    [self.graphView setNeedsDisplay];
}

- (void)setScale:(int)scale
{
    if (scale < 0) scale = 0;
    if (scale > 100) scale = 100;
    _scale = scale;
    [self updateUI];
}

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

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

-(IBAction)changedScale:(UIStepper *)stepper {
    self.scale = stepper.value; //this function works fine, but is not delegate/does not get called by view
}

-(float) scaleForGraph:(GraphView *)requestor {
    NSLog(@"HI"); //never gets here
}

-(NSMutableDictionary*) valuesForGraph:(GraphView *)requestor withWidth:(float) width {
    NSLog(@"Hello2"); //never gets here
    }
    return xyVals;
}

@end

Answer 1

您发布的代码中没有任何地方告诉您GraphView GraphingViewController是否是代表。因此，您要向nil发送消息。

你会想做类似的事情：

self.graphView.delegate = self;

在GraphingViewController设置代码中。

Answer 2

让您的控制器成为GraphView的实际代表。你可以在界面构建器中通过Ctrl-从GraphView拖动到对象（底部的橙色圆圈）而不是选择“委托”来完成它

查看代表未被调用

2 个答案: