ChangeDetectorRef instance in Angular

Question

I have one component and one regular TypeScript class in an Angular project. The component extends the class. Both have an independent instance of ChangeDetectorRef. Something like this:

import { ChangeDetectorRef } from '@angular/core';

export class MySuperClass {
    private cdr: ChangeDetectorRef;
    constructor() {}
    // .. other code here
}

And in another file:

import { ChangeDetectorRef } from '@angular/core';

export class MyComponent extends {
    @Component({...})

    constructor(private cdr: ChangeDetectorRef) {
        super();
    }
    // .. other code here
}

What confuses me is that the instance of ChangeDetectorRef that is used form the super class works even though it is neither injected nor instantiated explicitly.

Is this behavior due to nature of ChangeDetectorRef or the nature of how inheritance works in TypeScript, or something completely else?

Ben Ari Kutai · Accepted Answer · 2020-02-28 10:34:03Z

1

When angular injects

private cdr: ChangeDetectorRef

into MyComponent it actually runs over the the same param his father have.

If you create an instance of MySuperClass alone or if you change MySuperClass's cdr param name they both won't hold the same ChangeDetectorRef context

answered Feb 28, 2020 at 10:34

Ben Ari Kutai

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2 Comments

dzenesiz Over a year ago

So the parent class will get the child class instance of that variable even though I've explicitly declared two variables, both private?

Ben Ari Kutai Over a year ago

The opposite. The parent instance holds the variable and because the child inherits from its parent, it uses the same variable. so the child gets the parent instance in some sort of way

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