Angular dynamic component loading

Question

I am learning Angular, I have a CMS with API that returns contents of pages. pages can have short codes for forms, I have updated the API to replace short with a component selector

Sample page contents would look like

<div>bla bla bla </div>
<app-form [id]="1"></app-form>

In angular I have created FormComponent to load form accordingly, but when I get page contents with above mentioned selector I get the error

'app-form' is not a known element:.....

I did some research and found that I need some dynamic component loader but could not found any working examples as per my scenario, can any one help on how I can fix this issue

Answer 1

Indeed you would have to create those components dynamically. See this plunkr for an example code to do that: https://plnkr.co/edit/kkM1aR4yPcIqeBhamoDW?p=info

Although you need a ViewContainer for Angular to know where to insert that dynamic component. Which would not work because you can't bind to innerHTML and then change the code of the innerHTML manually. I am not sure but I think that would mess with angulars change detection.

I had to do this a few months ago and came up with a solution. I want to mention at this point that I am not sure if there is a better solution to this problem by now. Anyway, what I did is not to create dynamic components but rather create some custom rendering with *ngIfs. Let me explain: Your content contains tags. You decide how those tags look like. In my case I had a tag that the user can insert wherever he wants: [galerie="key_of_gallery"]. So the content could look like

some normal text
 <h2>Oh what a nice heading</h2>
 [galerie="summer_gallery"]
 text again

Now how can I render this? I would have to get something like

 <div>
    some normal text
    <h2>Oh what a nice heading</h2>
 </div>
 <galerie [key]="summer_gallery"></galerie>
 <div>
     text again
 </div>

So I created a custom component which creates this:

import { Component, Input } from '@angular/core';

@Component({
    selector: 'ffam-render-key-value',
    template: `<div *ngFor="let contentToRender of contentArray">
                    <div *ngIf="contentToRender.type==='normal'" [innerHTML]="contentToRender.value">
                    </div>
                    <galerie *ngIf="contentToRender.type==='gallery'" [key]="contentToRender.key"></galerie>
                </div>`
})
export class NoeRenderKeyValueComponent{
    @Input('contentArray') contentArray: any[] = [];
}

All this component needs is an array of tags which will be rendered with an *ngFor. Depending on the type of the tag either normal HTML or a component is created.

This component can be inserted like

    <ffam-render-key-value [contentArray]="keyValues['_text'].arrayWithCustomTags">
    </ffam-render-key-value>

To get this array of tags I have created a service with a function:

public getArrayWithCustomTags(keyValue): any[] {
        let arrayWithCustomTags: any[] = [];
        //check if custom Tag exists in the innerHTML
        if (keyValue.value.indexOf('[galerie=') !== -1) {
            //replace double quotes
            keyValue.value = keyValue.value.replace(/"/g, '"');
            //it exists, get array of all tags
            //regex that matches all [galerie="SOME KEY"] or [someAttribute="some text here"] -> You have to change this regex to fit all your tags
            let pattern = /(?:(\[galerie=\"[^\"]+\"\]))+/;
            //split with regexp to get array
            let arrayOfContents: string[] = keyValue.value.split(new RegExp(pattern, 'gi'));
            for (let i = 0; i < arrayOfContents.length; i++) {
                if (typeof arrayOfContents[i] === "undefined") {
                    arrayOfContents.splice(i, 1);
                    i--;
                }
                else {
                    let customTagToBeInserted: any = {};
                    if (arrayOfContents[i].indexOf('[galerie=') !== -1) {
                        //custom tag gallery
                        customTagToBeInserted.type = "gallery";
                        //get key only
                        customTagToBeInserted.key = arrayOfContents[i].replace("[galerie=\"", "").replace("\"]", "");
                    }
                    //else if some other attribute or even create a switch () {}
                    else {
                        //insert the normalHtml sanitized
                        customTagToBeInserted.type = "normal";
                        customTagToBeInserted.value = this.sanitizer.bypassSecurityTrustHtml(arrayOfContents[i]);
                    }
                    arrayWithCustomTags.push(customTagToBeInserted);
                }
            }
        }
        else {
            arrayWithCustomTags.push({ type: "normal", value: this.sanitizer.bypassSecurityTrustHtml(keyValue.value)});
        }
        return arrayWithCustomTags;
    }

This will create an array like:

[0]: {type: "normal", value:"SecureHTML"},
[1]: {type: "gallery", key:"summer_gallery"},
[2]: {type: "normal", value:"SecureHTML"},

Well I think you get the idea. If you create a whole CMS with more tags I would recommend creating a function that easily creates this whole process (regex etc.) for a tag. This example code is just meant for one tag.

The result is that the components are rendered right where the user places them. I hope this helps you.

Btw, if you have editable key value pairs for the user you might find this helpful: https://github.com/bergben/ng2-ck-editable. It's a little module I built to make any div editable using a ck-editor.