無法在打字稿中訪問全局變量

我在代碼中出現了一個奇怪的問題。我在類中聲明標記是可變的，所以它是全局的，並且可以在類內部的任何地方訪問。但問題是我可以在initMap中訪問標記，但不能在InitMap的函數中訪問它。錯誤告訴：TS2339屬性「標記」不存在類型void無法在打字稿中訪問全局變量

  export class StudentGraphicReportMapComponent implements OnInit { 
    locations: any[] = []; 
    markers:any[] = []; 
    constructor(private http: Http, private elementRef: ElementRef , private dashboardService: DashboardService) { 
    } 
    initMap() { 
    // ------ CAN ACCESS markers here 

    this.locations.forEach(function(location: Location) { 
     for (let b = 0; b < location.studentCount; b++) { 
      let marker = new google.maps.Marker({ 
      position: location, 
      label: 'A' 
      }); 
    // ----------CANNOT ACCESS markers here 
      this.markers.push(marker); //Error:Property 'markers' does not exist on type void 
     } 
    }); 

    } 
    ngOnInit() { 
    this.dashboardService.getStudentCoordinates().then(data => { 
     this.locations = data.data; 
     this.initMap(); 
    }); 
    } 

}

請幫我解決這個問題。親切的問候

來源

2017-08-17 Vugar Abdullayev

您應該檢查出**這**：https://stackoverflow.com/questions/20279484/how-to-access-the-correct-this-inside-a-callback（雙關語意：P） – Alex

您應該使用arrow functions獲得訪問this這樣的：

export class StudentGraphicReportMapComponent implements OnInit { 
    locations: any[] = []; 
    markers:any[] = []; 
    constructor(private http: Http, private elementRef: ElementRef , private dashboardService: DashboardService) { 
    } 
    initMap() { 
    this.locations.forEach((location: Location) => { 
     for (let b = 0; b < location.studentCount; b++) { 
      let marker = new google.maps.Marker({ 
      position: location, 
      label: 'A' 
      }); 
      this.markers.push(marker); //Error:Property 'markers' does not exist on type void 
     } 
    }); 

    } 
    ngOnInit() { 
    this.dashboardService.getStudentCoordinates().then(data => { 
     this.locations = data.data; 
     this.initMap(); 
    }); 
    } 

}

來源

2017-08-17 12:32:57 gilamran

謝謝，這也有幫助！ –

使本地變量指向此

initMap() { 
let _self = this; 
... 
}

，並使用_self.markers內部功能

來源

2017-08-17 12:34:42

是的，這工作很好。謝謝。 –

無法在打字稿中訪問全局變量

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