我被困在Angular 5
中的学习Crud操作的阶段我已经尝试了几个小时,但无济于事,看来我无法解决错误。
当我订阅来自服务的数据并尝试使用推送插入数据时。它说不确定。
addtasks.component.ts
import { Component } from '@angular/core';
import { AddTaskService } from '../../services/add-task.service';
import { Tasks } from '../../../Tasks/Tasks';
@Component({
selector: 'app-addtasks',
templateUrl: './addtasks.component.html',
styleUrls: ['./addtasks.component.css']
})
export class AddtasksComponent {
tasks: Tasks[];
title: string;
constructor(private addTaskService: AddTaskService) {
console.log("Add tasks page has been accessed...");
}
addTasks(event){
event.preventDefault();
var newTask = {
title: this.title,
isDone: false
};
this.addTaskService.addTask(newTask).subscribe(task => {
this.tasks.push(task);
this.title = '';
});
}
}
add-task.service.ts
import { Injectable } from '@angular/core';
import { Http, Headers } from '@angular/http';
import 'rxjs/add/operator/map';
@Injectable()
export class AddTaskService {
constructor(private http: Http) { console.log("Add Task service initialized..."); }
addTask(newTask){
var headers = new Headers();
headers.append('Content-Type', 'application/json');
console.log(newTask);
return this.http.post('http://localhost:2200/api/tasks', JSON.stringify(newTask), {headers: headers})
.map(res => res.json());
}
}
模型
tasks.ts
export class Tasks {
title: string;
isDone: boolean;
}
我的控制台中显示的错误
TypeError columnnumber:13文件名: " http://localhost:2200/main.bundle.js"亚麻布:193消息: " _this.tasks不确定"堆栈: " ../../../../../../../../src/app/app/components/addtasks/addtasks.component.ts/addtasks.component.prototype.addtasks.addtasks/<@http;@http://localhost:2200/main.bundle。n ../../../../rxjs/_esm5/subscriber.js/subscriber.protype.__next@http://localhost:2200/vendor.bundle.js:1585:1585:9 n ../。./../../../../rxjs/_esm5/subscriber.js/subscriber.protype.next@http://localhost:2200/vendor.bundle.js:1549:1549:1549:13 n../../../rxjs/_esm5/operators/map.js/mapsubscriber.prototype.__next@http://localhost:2200/vendor.bundle.js:4978:4978:9 n../../../rxjs/_esm5/subscriber.js/subscriber.prototype.next@http://localHost:2200/vendor.bundle.js:1549:13 nonload@http://http://localhost:2200/vendor.bundle.js:756626:756626:756626:756626:756626:756626:756626:21 n ../../../../ZONE.JS/dist/dist/dist.js/http://localhost:2200/polyfills.bundle.js:2504:17 nonInvoketask@http://http://localhost:2200/vendor.bundle.js:53623:24 n ../../../../../ZONE.JS/DIST/DIST/ZONE.JS/http://http://localhost:2200/polyfills.bundle.js:2503:17 n ../../../../ZONE.JS/DIST/ZONE.JS/http://localhost:2200/polyfills.bundle.js:2271:28 n ../。./../../../../zone.js/dist/zone.js/http://localhost:2200/polyfills.bundle.js:2578:24 ninvoketask@http://localhost:2200/polyfills.bundle。JS:3619:9 nglobalzoneawarecallback@http://localhost:2200/polyfills.bundle.js:3645:17 n __proto :object {stack:",…}
您应该在使用它之前初始化tasks
变量。在构造函数函数中初始化它。
constructor(private addTaskService: AddTaskService) {
console.log("Add tasks page has been accessed...");
this.tasks = [];
}
这就是为什么您有错误说它不确定的原因。