How to use a class as a type for properties of another class in typescript?
<p>I am new to typescript. I have defined some classes. I have used them as a type for the property of another class. e.g:</p>

<p><strong>fileone.ts</strong></p>

<pre><code>export class A {
   propertyOne: string;
   propertyTwo: string;
}
</code></pre>

<p>Now i have another class B in another file:</p>

<p><strong>filetwo.ts</strong></p>

<pre><code>import { A } from './fileone';
export class B {
    myProperty: A;
    mySecondProperty: string;
}
</code></pre>

<p>I have instantiated this class B in another file. 
I have the following code:</p>

<p><strong>myapp.ts</strong></p>

<pre><code>import { B } from './filetwo';
export class C {
    let myObj: B = new B();
    myObj.myProperty.propertyOne = 'hello';
    myObj.myProperty.propertyTwo = 'world'';
    console.log(myObj);
 }
</code></pre>

<p>Now when i try to set the property of A through B, it say the following error: </p>

<p><code>Cannot set the property "propertyOne" of undefined</code></p>

<p>Can we not do this like in java? And please explain why i cannot do what i am doing right now. And what is the correct approach for this. Please do not just give me solution to my problem but also an explanation.</p>