代表如何在目标 c 中工作？

Question

我正在尝试找出代表，因为我确实需要他们来完成我正在从事的项目，但对于我的一生，我无法弄清楚他们。无论我如何调整代码，都没有任何效果

ViewController.h：

#import <UIKit/UIKit.h>

@class ViewController;

@protocol testDelegate
-(void)sayHi;
@end

@interface ViewController : UIViewController 

- (IBAction)button:(id)sender;
@property (weak, nonatomic)id <testDelegate> delegate;

@end

ViewController.m：

#import "ViewController.h"
#import "DelegateController.h"


@interface ViewController ()

@end

@implementation ViewController

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

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

- (IBAction)button:(id)sender {
[self.delegate sayHi];
}
@end

DelegateController.h：

#import "ViewController.h"

@interface DelegateController : UIViewController <testDelegate>

@end

DelegateController.m：

#import "DelegateController.h"

@interface DelegateController ()

@end

@implementation DelegateController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        NSLog(@"init");
        ViewController *vc = [[ViewController alloc] init];
        [vc setDelegate:self];
}
    return self;
}
-(void)viewDidLoad
{
    [super viewDidLoad];
}

-(void)sayHi
{
    NSLog(@"hi");
}


@end

- (IBAction)button:(id)sender 方法是连接到一个按钮，但是当我点击时没有输出。我做错了什么？

Answer 1

ViewController.h：

#import <UIKit/UIKit.h>

@protocol testDelegate
    -(void)sayHi;
@end

@interface ViewController : UIViewController 

@end

ViewController.m：

#import "ViewController.h"
#import "DelegateController.h"

@interface ViewController () <testDelegate>

@end

@implementation ViewController

- (IBAction)pushNewViewController:(id)sender
{
    DelegateController *dc = [[DelegateController alloc] init];
    dc.delegate = self;
    [self.navigationController pushViewController:dc animated:YES];
}

- (void)sayHi
{
    NSLog(@"It works!");
}
@end

DelegateController.h：

#import "ViewController.h"

@interface DelegateController : UIViewController

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

@end

DelegateController.m：

#import "DelegateController.h"

@implementation DelegateController

- (IBAction)button:(id)sender
{
    if([_delegate respondsToSelector:@selector(sayHi)]) {
        [_delegate performSelector:@selector(sayHi)];
    }
}

@end

Answer 2

试试这个：

ViewController.h

#import <UIKit/UIKit.h>

@class ViewController;

@protocol testDelegate
-(void)sayHi;
@end

@interface ViewController : UIViewController 

- (IBAction)button:(id)sender;
@property (weak, nonatomic)id <testDelegate> delegate;

@end

ViewController.m

#import "ViewController.h"
#import "DelegateController.h"


@interface ViewController ()
@property (nonatomic, strong) DelegateController *dc;
@end

@implementation ViewController

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

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

- (IBAction)button:(id)sender
{
   [self.delegate sayHi];
}
@end

DelegateController.h

@interface DelegateController : UIViewController <testDelegate>

@end

DelegateController.m

#import "DelegateController.h"

@interface DelegateController ()

@end

@implementation DelegateController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self)
    {
        NSLog(@"init");
    }
    return self;
}
-(void)viewDidLoad
{
    [super viewDidLoad];
}

-(void)sayHi
{
    NSLog(@"hi");
}

@end

Answer 3

您的问题是 ViewController 创建了 DelegateController，然后在 DelegateController 中创建了一个新的、不同的 ViewController 实例，并将自己设置为该实例的委托。通常，您设置委托的方式是，DelegateController 会创建一个 ViewController 实例并将自己设置为委托。这假设首先创建了 DelegateController，但具体如何执行取决于您的应用结构，以及您如何从一个控制器移动到另一个控制器。

Answer 4

用下面的方法替换你的按钮点击方法

- (IBAction)button:(id)sender {
    // Check whether your Delegate method is implemeted or not
    if([delegate respondsToSelector:@selector(sayHi)])
    {
        // Call Delegate Method
        [delegate performSelector:@selector(sayHi)];
    }
}