angular - 类型错误 : Cannot read property 'post' of undefined

Question

您好，我只想使用一个简单的功能，http post 将我的日期发布到页面上。我希望服务器能够获取我发布的日期。

import { Component, OnInit } from '@angular/core';
import { MarginServcies } from '../../services/MarginService';
import { Response } from '@angular/http';
import { Http} from '@angular/http';
//import { Ng2SmartTableModule, LocalDataSource } from 'ng2-smart-table';


@Component({
    selector: 'margin',
    template: require('./margin.component.html')
})


export class MarginComponent implements OnInit {
    public http: Http;
    public MarginList = [];
    public date: string;
    public userdate: string;
    pad(i: number) {
        return i < 10 ? '0' + i : i;
    }
    onClick($event: any, userdate) {
        userdate = this.date;
        //console.log(this.date);
        this.http.post('api/date', userdate).subscribe();
    }

    //get the current date as default
    ngOnInit() {
        const selectedDate = new Date();
        this.date = `${selectedDate.getFullYear()}-${this.pad(selectedDate.getMonth() + 1)}-${this.pad(selectedDate.getDate())}`;
    }

    public constructor(private marginService: MarginServcies) {

        //get Margindata from server
        this.marginService.getMargin().subscribe(results => {
            this.MarginList = results.json();
            //console.log(results.json());
        });


    }

}

这是我的组件。我正在使用 webpack，angular 4。我想在 onClick() 函数中使用 post 函数。单击后我可以发布日期。现在我检查 console.log() 工作正常。错误是:

MarginComponent.html:15 ERROR TypeError: Cannot read property 'post' of undefined
    at MarginComponent.onClick (margin.component.ts:25)
    at Object.eval [as handleEvent] (MarginComponent.html:15)
    at handleEvent (vendor.js?v=8G5nuphpleAMB8hDVj0v8l9es64guglhqGWIwYdey3M:22850)
    at callWithDebugContext (vendor.js?v=8G5nuphpleAMB8hDVj0v8l9es64guglhqGWIwYdey3M:24142)
    at Object.debugHandleEvent [as handleEvent] (vendor.js?v=8G5nuphpleAMB8hDVj0v8l9es64guglhqGWIwYdey3M:23730)
    at dispatchEvent (vendor.js?v=8G5nuphpleAMB8hDVj0v8l9es64guglhqGWIwYdey3M:19750)
    at vendor.js?v=8G5nuphpleAMB8hDVj0v8l9es64guglhqGWIwYdey3M:20342
    at HTMLButtonElement.<anonymous> (vendor.js?v=8G5nuphpleAMB8hDVj0v8l9es64guglhqGWIwYdey3M:27870)
    at ZoneDelegate.invokeTask (vendor.js?v=8G5nuphpleAMB8hDVj0v8l9es64guglhqGWIwYdey3M:83738)
    at Object.onInvokeTask (vendor.js?v=8G5nuphpleAMB8hDVj0v8l9es64guglhqGWIwYdey3M:15077)

有人可以帮我吗？谢谢!

Answer 1

仅通过声明 public http: Http 不会使 Http 提供程序实例在组件内可用。您必须在构造函数中注入(inject) http 服务，这将带来 http 对象。

public constructor(
    private marginService: MarginServcies, 
    private http: Http //<-- added Http service.
) {
 //your code as is
}

Remove the declaration of public http: Http(http declaration) from start of class public http: Http