Question

对此感到抱歉。我想做的事：在视图的文本字段中输入一个字符串（EnterCommandViewController）并单击“保存”按钮，这将关闭当前视图并返回另一个视图（DetectionViewController）并在当前视图（DetectionViewController）中显示UILabel中的字符串。所以我在EnterCommandViewController中定义了委托协议，我的问题是为什么用于检查某人是否正在侦听的respondToSelector不起作用。

我真的是iOS的初学者，我现在正在编写一个委托，将UITextField形式的文本发送到UILabel，但我发现respondToSelector无法被调用使用NSLog进行测试。

以下是我的参考代码：

EnterCommandViewController.h

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

@protocol EnterCommandDelegate <NSObject>

-(void) commandEntered:(NSString*)command;

@end

@interface EnterCommandViewController : UIViewController <RscMgrDelegate>
{
 RscMgr* rscMgr;
 __weak IBOutlet UITextField *inputTextField;

 __unsafe_unretained id<EnterCommandDelegate> delegate;
}

-(void)sendMessage:(NSString*)message;

- (IBAction)cancelPressed;

- (IBAction)savePressed;

@property (nonatomic,assign)id delegate;

@end

EnterCommandViewController.m

#import "EnterCommandViewController.h"

@interface EnterCommandViewController () <UITextFieldDelegate>
{
    @private
    BOOL connected;
}

@end

@implementation EnterCommandViewController

@synthesize delegate;

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

inputTextField.text=@"";
[inputTextField becomeFirstResponder];
}

-(void) viewWillAppear:(BOOL)animated{
[super viewWillAppear:animated];
inputTextField.delegate = self;
}

-(void) viewWillDisappear:(BOOL)animated{
[super viewWillDisappear:animated];
inputTextField.delegate = nil;
}

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

- (IBAction)cancelPressed {
[self dismissViewControllerAnimated:YES completion:^{}];
}

- (IBAction)savePressed {
//is anyone listening

NSLog(@"the command is %@",inputTextField.text);
  NSLog(@"Checking -- SomeMethod is listening");
if([delegate respondsToSelector:@selector(commandEntered:)]){
    NSLog(@"SomeMethod is listening");
    //send delegate function with the command entered by the user
    [delegate commandEntered:inputTextField.text];
}
[self dismissViewControllerAnimated:YES completion:^{}];
}

DetectionViewController.h

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

@interface DetectionViewController : UIViewController <EnterCommandDelegate>{

__weak IBOutlet UILabel *showCommand;
}
- (IBAction)showSettings:(UIBarButtonItem *)sender;

@end

DetectionViewController.m

#import <Foundation/Foundation.h>
#import "DetectionViewController.h"

@implementation DetectionViewController


- (IBAction)showSettings:(UIBarButtonItem *)sender {

}

-(void) viewDidLoad{
[super viewDidLoad];
showCommand.text=@"";
EnterCommandViewController* enterCVC = [[EnterCommandViewController alloc] init];
    enterCVC.delegate = self;
}

#pragma mark - EnterCommandDelegate function(s)

-(void) commandEntered:(NSString *)command{
//    showCommand.text = command;
dispatch_async(dispatch_get_main_queue(), ^{
    NSLog(@"command: %@",command);
    [self->showCommand setText:command];

});
}
@end

AppDelegate.m

#import "AppDelegate.h"

@interface AppDelegate ()

@end

@implementation AppDelegate


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
// Override point for customization after application launch.
return YES;
}

Answer 1

您没有正确设置delegate。

EnterCommandViewController* enterCVC = [[EnterCommandViewController alloc] init];
    enterCVC.delegate = self;

这不是在你的情况下设置delegate的方法，因为你没有使用创建的enterCVC, instead a new instance is created from the storyboard when you are transitioning to EnterCommandViewController实例（从你的评论明确表示你正在使用故事板为此）。

那么你可以做的就是delegate来自prepareForSegue中的DetectionViewController

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
     // Get reference to the destination view controller
     EnterCommandViewController* enterCVC = [segue destinationViewController];
     enterCVC.delegate = self;
}

respondsToSelector无法调用？

1 个答案: