xcode 委托方法协议不起作用 - 目标 C

Delegate Method Protocol Not Working - Objective C

提问by kamalbhai

I am working on a splitViewapplication for my iPad. I have implemented a UIButtoncalled as Upload. On clicking on it, a UITableViewappears inside a UIPoverController. On clicking on any of the contents, I want to display some respective site in my UIwebViewin UIDetailView. For this I have implemented a delegate method protocol. I have used the following lines of code in UploadTableViewController.hfile::

我正在splitView为我的iPad. 我已经实现了一个UIButton叫做 as Upload。单击它时， a 会UITableView出现在 a 中UIPoverController。单击任何内容时，我想在我UIwebView的UIDetailView. 为此，我实施了一个delegate method protocol. 我在UploadTableViewController.h文件中使用了以下代码行::

@protocol UploadTableViewDelegate <NSObject>
@required
- (void)selected:(NSString *)his;
@end


 @interface UploadSpaceTableViewController : UITableViewController{
id<UploadSpaceTableViewDelegate> delegate;
}

@property (retain) id delegate;
@end

In the corresponding .mfile I have used the following lines of code ::

在相应的.m文件中，我使用了以下代码行 ::

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{

if (delegate != nil) {
    NSString *hisSelected = [keys objectAtIndex:indexPath.row];
    NSLog(@"%@ lolwa", hisSelected);
    [delegate selected:hisSelected];
}

}

in the .mfile of class where I have implemented the function Selected, the code is ::

在.m我实现该函数的类文件中Selected，代码是 ::

- (void)selected:(NSString *)Key {    
  NSLog(@"hello");    
  [self.UploadSpaceTableViewPopover dismissPopoverAnimated:YES];
}


-(IBAction)uploadpressed:(id)sender{  
Upload.delegate = self;
self.Upload = [[UploadSpaceTableViewController alloc] 
                         initWithStyle:UITableViewStylePlain];
self.UploadTableViewPopover = [[UIPopoverController alloc] 
                                initWithContentViewController:UploadSpace];               

[self.UploadTableViewPopover presentPopoverFromBarButtonItem:sender 
                                permittedArrowDirections:UIPopoverArrowDirectionAny animated:YES];
 }

However, I am unable to get hello(written in the function Selected) NSLoggedin gdb. This is the first time that I am using this delegate method protocol. I am unable to sort this out. Can someone help me out ? Thanks and regards.

但是，我无法在 gdb 中获取hello（写在函数中Selected）NSLogged。这是我第一次使用这个delegate method protocol。我无法解决这个问题。有人可以帮我吗 ？感谢致敬。

回答by CodaFi

[delegate keySelected:hisKeySelected];is your first problem. You don't declare a delegate method named -keySelected:, you declare a delegate method named -Selected:.

[delegate keySelected:hisKeySelected];是你的第一个问题。您没有声明名为 的委托方法-keySelected:，而是声明了名为 的委托方法-Selected:。

Your second problem is the fact that you are most definitely not the delegate of your table view. In order for a delegate method like -didSelectRowAtIndexPath:to be called, you must be the table's delegate.

您的第二个问题是您绝对不是表视图的代表。为了-didSelectRowAtIndexPath:调用类似的委托方法，您必须是表的委托。

PS, don't begin instances, or method names, with an uppercase letter. In ObjC, uppercase letters indicate a class.

PS，不要以大写字母开头实例或方法名称。在 ObjC 中，大写字母表示一个类。

EDIT: this is what your UploadSpaceTableViewControllerheader should look like:

编辑：这是你的UploadSpaceTableViewController标题应该是什么样子：

@protocol UploadTableViewDelegate <NSObject>
@required
- (void)selected:(NSString *)his;
@end

@interface UploadSpaceTableViewController : UITableViewController<UITableViewDataSource, UITableViewDelegate>
@property (nonatomic, assign) id <UploadSpaceTableViewDelegate>delegate; //delegates are weak!!!
@end

And the .m, I will skip a lot of the unnecessary stuff:

而 .m，我会跳过很多不必要的东西：

-(void)viewDidLoad {
    [self.tableView setDelegate:self];
    [self.tableView setDataSource:self];
}
//other code

Furthermore, your delegate is declared retain, which is an absolutel No-No in ObjC. Declare is weak if using ARC, or assign if not.

此外，您的委托被声明为保留，这在 ObjC 中是绝对不可以的。如果使用 ARC，则声明是弱的，否则，如果不是，则分配。

You are also producing a nil delegate in in your -uploadPressed:method by setting it before you explicitly own or initialize the object. Here's how it should look:

-uploadPressed:通过在显式拥有或初始化对象之前设置它，您还在方法中生成了一个 nil 委托。这是它的外观：

self.Upload = [[UploadSpaceTableViewController alloc]initWithStyle:UITableViewStylePlain];
Upload.delegate = self;

回答by Pfitz

Delegation works like this

委托是这样工作的

• declare a protocol - you have done this
• declare a delegate property - you have done this

• In the class which you want to be the delegate say it conforms to the protocoll

  @interface MyClass : MySuperClass <UploadTableViewDelegate>

• set the delegate property so the delegate class can get the delegate messages

  uploadSpaceTVC.delegate = self;

• call the delegate methods in your non delegate class (UploadSpaceTableViewController)

  [self.delegate selected:@"test"];

• 声明一个协议 - 你已经完成了这个
• 声明一个委托属性 - 你已经完成了

• 在你想成为委托的类中说它符合协议

  @interface MyClass : MySuperClass <UploadTableViewDelegate>

• 设置委托属性，以便委托类可以获取委托消息

  uploadSpaceTVC.delegate = self;

• 在非委托类 ( UploadSpaceTableViewController) 中调用委托方法

  [self.delegate selected:@"test"];