什么是angular2中的可投影节点 [英] What are projectable nodes in angular2

问题描述

在阅读 ViewContainerRef 和 ComponentFactory ，其中，例如，我们有方法

On reading the documentation of ViewContainerRef and ComponentFactory, where , for example we have the method

ViewContainerRef#createComponent ，其中包含3个参数:componentFactory，injector和projectableNodes.

ViewContainerRef#createComponent which takes 3 arguments : componentFactory , injector and projectableNodes.

我尝试查找projectableNodes的含义以及它们在博客，教程和源代码中的用法，但找不到太多.

I have tried looking up what projectableNodes mean and how they are used in blogs, tutorials and source code but could not find much.

在查找 diff以获得ngComponentOutlet指令时，我可能会收集到projectableNodes中的字符串已投影"或呈现到创建的组件视图上(例如ng-content可能是).如果是这样，那会令人困惑，因为我们有 ViewContainerRef#createEmbeddedView 相同.

On looking up the diff for for ngComponentOutlet directive, All I could gather was that the string in projectableNodes is "projected" or rendered on to the created components view ( like ng-content may be). If so that is confusing as we have ViewContainerRef#createEmbeddedView for the same.

我想知道这些projectedNodes是什么，并举例说明它们的用法.

I would like to know as to what are these projectedNodes and have an example of their usage.

推荐答案

可投影节点是节点元素(即实现ng-content上.

Projectable nodes are the node elements ( i.e elements implementing the node interface ), which are "projected" or in other words, transcluded onto the ng-content that we have in the template of our component.

例如，我们可以通过以下方式创建节点元素:

For example we can create a node element the following way :

var myNode = document.createElement('div');
var text = document.createTextNode('this is my text');
myNode.appendChild(text);

然后我们可以通过以下方式使用上述节点:

Then we can use the above node, the following way :

constructor(private vcr:ViewContainerRef ) {

}
ngAfterViewInit() {

  let cmpFactory = this.vcr.resolveComponentFactory(MyDynamicComponent);
  let injector = this.vcr.parentInjector;

  var myNode = document.createElement('div');
  var text = document.createTextNode('this is my text');
  myNode.appendChild(text);
  this.vcr.createComponent(cmpFactory,0,injector,[ [ myNode ] ])
}

投影节点可以使用二维数组，因为我们可以进行多槽包含，即多个ng-content.

A two dimensional array is accepted for projected nodes as we can have multi-slot transclusion, that is more than one ng-content.

这里是如何将可投影节点与ViewContainerRef#createComponent一起使用的完整示例.此示例动态创建一个其中包含transclsion/ng-content的组件:

Here is a full example of how to use the projectable nodes with ViewContainerRef#createComponent. This example dynamically creates a component that has transclsion/ng-content in it:

import { Component, ViewContainerRef, ComponentFactoryResolver } from '@angular/core';
import { ComponentFactory,ComponentRef, Renderer } from '@angular/core';

@Component({
    selector: 'sample',
    template: '<ng-content></ng-content><ng-content></ng-content>'
})
export class Sample { }

@Component({
    selector: 'demo',
    template: '<p>Demo</p>',
    entryComponents: [Sample]
})
export class DemoComponent {

    constructor(private vcr: ViewContainerRef, private cfr: ComponentFactoryResolver, private r: Renderer) { }

    ngAfterViewInit() {
        let cmpFactory = this.cfr.resolveComponentFactory(Sample);
        let injector = this.vcr.parentInjector;
        let demoCompEl = this.vcr.element.nativeElement;

        let projectedElA = this.r.createElement(demoCompEl,'p');
        this.r.createText(projectedElA,'projectable content A');
        this.r.detachView([projectedElA]);

        let projectedElB = this.r.createElement(demoCompEl,'p');
        this.r.createText(projectedElB,'projectable content B');
        this.r.detachView([projectedElB]);

        let projectedC = document.createElement('div');
        let text = document.createTextNode('projectable content C');
        projectedC.appendChild(text);

        let cmpRef = this.vcr.createComponent(cmpFactory,0,injector,[[projectedElA],[projectedElB,projectedC]]);

    }


}

输出:

Demo

projectable content A

projectable content B

projectable content C

要注意的另外一点是，在我们传递给可投影节点的2d数组中，每个1d数组条目都有一个特定视图的根元素，这些根元素属于/将在一个视图中一起呈现.单个ng-content块

The additonal thing to notice is that in the 2d array that we pass for projectable nodes, each 1d array entry has the root elements of a particular view that belong together/ will be rendered together in a single ng-content block

这篇关于什么是angular2中的可投影节点的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！