Xcode 6'类'ViewController'的重复接口定义错误 [英] error with Xcode 6 'Duplicate interface definition for class 'ViewController'

问题描述

我正在使用 Xcode 6 按照 2012 年的基本教程编写应用程序.该教程是使用 Xcode 4.3 制作的，我确信我完全按照我通过观察问题区域进行的仔细检查来遵循它.我对这种类型的编程很陌生，因为我通常处理游戏开发和机器人，但之前做过一些.

I'm programming an app following a basic tutorial from 2012 using Xcode 6. The tutorial was made using Xcode 4.3 and I'm sure I have followed it exactly as I have double checked by watching through the problem areas. I'm quite new to this type of programming as I usually deal with game development and robots but have done a little before.

错误:

类ViewController"的重复接口定义

Duplicate interface definition for class 'ViewController'

这是代码:

 #import "ViewController.h"

 @interface ViewController // First error here.

 @end

 @implementation ViewController

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

   -(void) presentMessage:(NSString *)message {
       UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"My Title"         message: message delegate: nil cancelButtonTitle:@"Ok" otherButtonTitles: nil ];

[alert show];
[alert release]; // second error.
}

-(void) scheduleLocalNotificationWithDate:(NSDate *)fireDate {
UILocalNotification *notification = [[UILocalNotification alloc] init];

...    

[notification release]; // third error
}

-(IBAction) buttonTapped:(id)sender {

    dateFormatter...

[dateFormatter release]; // fourth error
 }
   @end

对于奇怪的格式很抱歉，但我无法将其格式化为代码.

Sorry about the weird formatting but I couldn't get this to format into code.

提前致谢

推荐答案

您需要将 () 添加到您的 @interface ViewController 行.

You need to add () to your @interface ViewController line.

@interface ViewController()

这在 iOS 中称为私有类别，用于在您的实现文件中定义私有方法和属性.

This is called a private category in iOS, and it's used to define private methods and properties in your implementation file.

在您的 .h 文件中，您会发现接口声明为 @interface ViewController，这就是编译器认为您声明它两次的原因.使用私有类别(@interface ViewController())告诉编译器您实际上是在扩展已经定义的接口(称为 ViewController)的功能，添加私有方法和属性.

In your .h file, you'll find the interface declared as @interface ViewController, and that's why the compiler thinks you're declaring it twice. Using a private category (@interface ViewController()) tells the compiler that you're actually extending the functionality of your already defined interface (called ViewController), adding private methods and properties.

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