Angular 6: Update NG Style with function - css

Question

I'm here today because I'm wondering something about the NG Style with Angular (my version being the 6). How can i update [ngStyle] when I use a function to return a value.
As always, here is a simplified example of my problem:
I generate div from an array of objects.
For each section, there are two div: one on the left and one on the right.
The size of the left div changes depending on the content, so it can do both 50px and 125px.
I want the right div to fit the size of the one on his left, always half that size (2 in getLeftDivHeight).
Obviously, this will be done in each section (Container).
How can I make the ngStyle update when the div's height to the left changes (due to resizing, adding content, or page display time)? )
Here is the code:
HTML
<section class = "Container" *ngFor="let oneContent of allContent">
<div id = "{{oneContent.id}}" style="float: left">
<p> {{oneContent.Content}} </ p>
</div>
<div style="float: right" [ngStyle]="height: getLeftDivHeight(oneContent.id, 2)">
</div>
</div>
Typescript (only the related function)
getLeftDivHeight(id: string, divisionNumber: number): string {
height = document.GetElementById(id).getBoundingClientRect().height /
divisionNumber;
return height + 'px';
}
Note that I am not looking for an HTML solution, but an Angular one, the code above is just an example to explain my problem.
Thank you in advance

Answer 1

You could return the whole style string, for example height: 100px, from the getLeftDivHeight method
getLeftDivHeight(id: string, divisionNumber: number): string {
height = document.GetElementById(id).getBoundingClientRect().height / divisionNumber;
return `height: ${height}px`;
}
or you could use the below syntax in the template
[style.height.px]="getLeftDivHeight(parameters)"
return only numerical height value from the method.

Answer 2

So, I finally manage to do it, using a directive.
I used ElementRef to access the HTML Object of my right div.
import {ElementRef,Renderer} from '#angular/core';
constructor(private el: ElementRef,public renderer: Renderer) {}
Then, I used Dom to access the left div height
this.el.nativeElement.parentElement.childElement[0].clientHeight;
Then I use this.renderer.setElementStyle() to apply style
I also learn that use offscrollheight to do the math is not a good idea !