How can I use NgFor without creating arrays to generate matrix UI pattern

Question

I would like to implement UI matrix pattern, which should generate dynamically. By receiving input parameter it should decide what would be UI matrix pattern dimensions: For

Answer 1

Create custom STRUCTURAL DIRECTIVE which repeats template N times.

import {TemplateRef, ViewContainerRef, Directive, Input} from 'angular2/core';

@Directive({
   selector: '[mgRepeat]'
})
export class mgRepeatDirective {
   constructor(
       private _template: TemplateRef,
       private _viewContainer: ViewContainerRef
   ) { }

   @Input('mgRepeat')
   set times(times: number) {
       for (let i = 0; i < times; ++i)
           this._viewContainer.createEmbeddedView(this._template);
   }
}

Use as follows

<div id="game-pattern" >
  <div class="pattern-row" *mgRepeat="verticalElementLocation">
     <div class="big-circle" *mgRepeat="horizontalElementLocation"> 
        <div class="small-circle"></div>
     </div>
 </div>
</div>

Answer 2

Building arrays just to iterate over them seems lavish. Creating a Directive to replace ngFor is sort of redundant.

Instead you could use a Pipe returning an Iterable and use it like this:

<div *ngFor="let i of 30|times">{{ i }}</div>

For an implementation of such a Pipe have a look at my other answer on Repeat HTML element multiple times using ngFor based on a number.

Answer 3

After reading all answers I managed to solve it:

 public chooseGamePattern() {
    if (this.cardType === 3) {
        this.horizontalElementLocation = 9;
        this.verticalElementLocation = 3;
        this.rows = new Array(this.verticalElementLocation);
        this.elements = new Array(this.horizontalElementLocation);
    }

It works for me. Thank You all!!!

Answer 4

You can either create an helper array like shown in Repeat HTML element multiple times using ngFor based on a number using new Array(count).fill(1) and use ngFor to iterate over this array or you can implement your own structural directive like NgFor that doesn't iterate over an array but instead uses a count as input.

Answer 5

In my case i wanted to make a price rating dynamic something like this

'Price Rating : $$$' or 'Price Rating : $$' without making an array to repeat this "$"

so i knew that my rating is 5 at most and this working well for me .

   <ng-container *ngFor="let i of [1, 2, 3, 4, 5] | slice: 0:place.priceRating">
      $
   </ng-container>

priceRating maybe from 0 to 5

hope that help