of-select 未在 Angular 2 中更新

Question

你好，我是 angular 2

的新人

我可以在 ng-select 控件中添加 formGroup 并预定义添加的值。

太好了。但是当单击按钮时，新值将推入 ng-select 但 ng-select 不会更新 .

这是我的笨蛋

https://plnkr.co/edit/Hwfk1T2stkiRcLTxuFmz

//our root app component
import {Component, OnInit, NgModule, ViewChild} from '@angular/core';
import {BrowserModule} from '@angular/platform-browser';
import {FormControl, FormGroup, ReactiveFormsModule} from '@angular/forms';
import {SelectModule} from 'ng-select';

@Component({
    selector: 'my-app',
    template: `
<h1>ng-select demo app</h1>
<form style="padding:18px;max-width:800px;"
    [formGroup]="form">

    <div style="margin:5px 0;font-weight:600;">Single select example</div>
    <ng-select
          [options]="options0"
          [multiple]="false"
          placeholder="Select one"
      formControlName="selectSingle"
     >
    </ng-select>

   <button (click)="pushValue()">Click</button>



    <div>Events:</div>
    <pre #preSingle>{{logSingleString}}</pre>

</form>`
})
export class App implements OnInit {

    form: FormGroup;

    multiple0: boolean = false;
    options0: any[] = [];
    selection: Array<string>;

    @ViewChild('preSingle') preSingle;

    logSingleString: string = '';

    constructor() {
      this.options0.push({"label":'test',"value":'Test'});
       console.log("Object:::"+JSON.stringify(this.options0));
    }

    ngOnInit() {
        this.form = new FormGroup({});
        this.form.addControl('selectSingle', new FormControl(''));
        console.log("Object:::"+JSON.stringify(this.options0));
    }

    pushValue()
    {
       console.log("pushValue call.");
       this.options0.push({"label":"test","value":"Test"});
       console.log("Object:::"+JSON.stringify(this.options0));
    }
}

@NgModule({
  imports: [
    BrowserModule,
    ReactiveFormsModule,
    SelectModule
  ],
  declarations: [ App ],
  bootstrap: [ App ]
})
export class AppModule {}

哪里错了？？？

Answer 1

查看 ng-select 源代码我注意到了

ngOnChanges(changes: any) {
  if (changes.hasOwnProperty('options')) {
     this.updateOptionsList(changes['options'].isFirstChange());
  }

因此，为了更新选项列表，您应该触发 ngOnChanges。可以通过创建对 options0

的新引用来完成

this.options0 = this.options0.concat({"label":"test","value":"Test"});

或

this.options0 = [...this.options0, {"label":"test","value":"Test"}];

Modified Plunker

Answer 2

你可以使用Array.slice()更新数组实例，让angular检测到数组的变化。

this.options0 = this.options0.slice();

Answer 3

变更检测

Ng-select 组件实现了 OnPush 变化检测，这意味着脏检查检查不可变数据类型。这意味着如果您进行对象突变，例如：

this.items.push({id: 1, name: 'New item'})

组件将不会检测到更改。相反，您需要这样做：

this.items = [...this.items, {id: 1, name: 'New item'}];

这将使组件检测到更改和更新。有些人可能担心这是一个昂贵的操作，但是，它比运行 ngDoCheck 和不断区分数组的性能要好得多。

of-select 未在 Angular 2 中更新

ng-select not updating in Angular 2

javascript

angular-ngselect

angular