4

当我单击添加按钮以使用输入将数据从父级发送到子级时，我在 angular2 中构建基本的 Todo 应用程序我得到没有字符串提供者！(child->string)，并且没有显示数据只显示子类的按钮，是什么意思

这是父组件：

@Component({
selector : 'parent-component',
directives : [child],
template : `
<h1 class= "text-center">ToDo App</h1>
<div class = "form-group">
<lable>Task</lable>
<input type = "text" class = "form-control" #task>
<lable>Detail</lable>
<input type = "text" class = "form-control" #detail >
<button type = "submit" class  = "btn btn-default" 
(click) = "addtask(task,    detail)">Add Task</button>


<child-component *ngFor = "#todo of Array" [taskobject] = "todo">
Loading... </child-component>
</div>

`
})
class parent{
//taskobj : {task : string, details : string, id:  number};
Array : child[];
id : number;

constructor(){

    //i want this to initialize asa parent create
    this.Array = [];
}

addtask(task : HTMLInputElement, detail : HTMLInputElement){
    // this.taskobj.task= task.value;
    // this.taskobj.details = detail.value;
   this.id = Date.now();
    // this.array.push();

    this.Array.push(new child(task.value, detail.value, this.id ));
    console.log(Array)
    task.value = '';
    detail.value = '';

}

这是子组件：

@Component({

selector : 'child-component',
inputs : ['taskobject'],
//outputs : ['objectsend'],
template : `
  {{taskobject.task}}
  {{taskobject.details}}
  <button type = "button" class = "btn btn-default" 
  (click) = "deletetask()">Delete</button>
  <button type = "button" class = "btn btn-defualt" 
  (click) = "updatetask()">Update</button>

  `
  })
class child{

//we are creating a instance just as configured as child component 
task : string;
detals : string;
id : number;
//array : any[];

constructor(task : string, detail : string, id : number){
    this.task = task;
    this.detals = detail;
    this.id = id;
}

}
4

2 回答 2

3

child由于 Angular2自己实例化该类并尝试将您在其构造函数级别定义的参数注入其中，因此您遇到了错误。他们没有相关的提供者...

否则，如果您想从父组件引用子组件，您可以利用@ViewChild装饰器通过注入从父组件引用子组件：

import { Component, ViewChild } from 'angular2/core';  

(...)

@Component({
  selector: 'my-app',
  template: `
    <h1>My First Angular 2 App</h1>
    <child></child>
    <button (click)="submit()">Submit</button>
  `,
  directives:[App]
})
export class AppComponent { 
  @ViewChild(SearchBar) searchBar:SearchBar;

  (...)

  someOtherMethod() {
    this.searchBar.someMethod();
  }
}

这是更新的 plunkr：http ://plnkr.co/edit/mrVK2j3hJQ04n8vlXLXt?p=preview 。

您可以注意到@Query参数装饰器也可以使用：

export class AppComponent { 
  constructor(@Query(SearchBar) children:QueryList<SearchBar>) {
    this.childcmp = children.first();
  }

  (...)
}

希望它可以帮助你，蒂埃里

于 2016-02-02T08:47:40.523 回答
1

构造函数参数从指定的 DI 提供程序中解析bootstrap(AppComponent, [SomeProvider, SomeOtherProvider, ...]);

输入是自动分配的，但仅在生命周期调用之后ngOnInit()。

@Component({
  selector : 'child-component',
  inputs : ['taskobject'],
  //outputs : ['objectsend'],
  template : `
    {{taskobject?.task}}
    <!-- use the safe-navigation operator ?. to avoid errors 
      when `taskobject` is not yet set
    -->
    {{taskobject?.details}}
    <button type = "button" class = "btn btn-default" 
    (click) = "deletetask()">Delete</button>
    <button type = "button" class = "btn btn-defualt" 
    (click) = "updatetask()">Update</button>
    `
})
class child {
  //we are creating a instance just as configured as child component 
  taskobject: any;
  task : string;
  detals : string;
  id : number;
  //array : any[];

  constructor() {
  }

  // when this callback is called the 
  // `taskobject` (from `inputs : ['taskobject'],`) 
  // is initialized 
  ngOnInit() {
    this.task = taskobject.task;
    this.detals = taskobject.detail;
    this.id = taskobject.id;
  }
}
于 2016-02-02T09:12:24.850 回答