Question

使用Angular 4和Typescript时，我定义了这个函数

     

   @Injectable()
   export class XService {
     display: (message?: string) => Promise<boolean>;    
   }

  @Component({
     templateUrl: './app/x/x.html',
     styleUrls: ['./app/x/x.component.css']
  })
  export class XEditComponent  { 
    constructor(private _xService: XService ) { }
    deleteX(): void {
         let msg = "Do you really want to delete !";
         this._xService.display(msg).then((responseOk) => {
         //.....
        });
   }
}

但我总是得到一个TypeError＆＃39;显示＆＃39;不是一个功能。

Answer 1

您实际上没有定义函数。您只定义了它的类型。现在display将是未定义的。

定义功能：

export class XService {
    display: (message?: string) => Promise<boolean> = (message) => {  
      // Do something more useful here
      return Promise.resolve(true);
    }
}

或者您可以删除类型声明并让编译器推断出类型：

export class XService {
    display = (message: string | undefined): Promise<boolean> => {
        // Do something more useful here
        return Promise.resolve(true);
    }
}

或者您可以将声明更改为方法语法而不是属性语法：

export class XService {
    display(message: string | undefined): Promise<boolean>  {
        // Do something more useful here
        return Promise.resolve(true);
    }
}

胖箭不是一个功能

1 个答案: