Question

设置：

将PickerView（spinSelector）和标签（chosenItem）添加到ViewController中。为PickerView委托创建单独的委托类文件（SpinDelegate m＆amp; h）。创建委托的实例（SpinDelegate * mySpinDelegate）将委托属性分配给委托实例

ViewController.h

@interface ViewController : UIViewController
{
    SpinDelegate *mySpinDelegate;
}

@property (nonatomic, weak) IBOutlet UILabel *chosenItem;
@property (nonatomic, strong) IBOutlet UIPickerView *spinSelector;

ViewController.m

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

    self.spinSelector.delegate=mySpinDelegate;
    self.spinSelector.dataSource=mySpinDelegate;
}

SpinDelegate.h

@interface SpinDelegate : UIViewController <UIPickerViewDataSource, UIPickerViewDelegate>
{
    ChoiceData *choiceItems;
}

@end

SpinDelegate.m

    #pragma mark - PickerView Delegate
    - (NSString *)pickerView:(UIPickerView *)pickerView 
titleForRow:(NSInteger)row 
forComponent:(NSInteger)component{

        return [choiceItems.choiceList objectAtIndex:row];
    }

接下来是使用方法：

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component;

这是UIPickerViewDelegate协议的一部分。使用此方法，只需将ViewController中的UILabel（selectedItem）更改为行的值即可。类似于＆＃34;挑选的项目是％i＆＃34;，行

我已经通过大量关于UIViewController到UIViewController消息的帖子和问题进行了阅读和搜索，并查看了协议/代表，单身人士，NSNotificationCenter ...它只是在我看来，我缺少一个语法来解决父/超？ ViewController创建了委托的实例，委托没有范围吗？

请教育我这个。：）

Answer 1

您可以这样做：

<强> ViewController.h

#import "SpinViewController.h"
@interface ViewController : UIViewController<SpinViewControllerDelegate>
{
}

@property (nonatomic, weak) IBOutlet UILabel *chosenItem;
@property (nonatomic, strong) IBOutlet UIPickerView *spinSelector;

<强> ViewController.m

- (void)someFunction
{
    mySpinViewController=[[SpinViewController alloc]init];
    mySpinViewController.delegate=self;
    // show or present mySpinViewController
}

//implement the followed protocol's method
-(void) optionSelected:(NSString*)cellValue{

}

<强> SpinViewController.h

@protocol SpinViewControllerDelegate <NSObject>

@optional
-(void) optionSelected:(NSString*)cellValue;
@end

@interface SpinViewController : UIViewController <UIPickerViewDataSource, UIPickerViewDelegate>
{
    ChoiceData *choiceItems;
}

@property (nonatomic,retain)id <SpinViewControllerDelegate> delegate;

@end

<强> SpinViewController.m

-(void) pickerValueSelectedOrSimilarFn:(NSString*)cellValue{
  // this is how you give a callback to classes following the protocol
  [self.delegate optionSelected:cellValue];
}

委托'Parent'ViewController最佳实践

1 个答案: