Why passing custom object in @Input doesn't work?

I am trying to pass a custom object through @Input. But, I'm getting null as output.

This is my child component class:

import { Component, OnInit, Input } from '@angular/core';
import { Element } from '../app.element';

@Component({
  selector: 'app-server-element',
  templateUrl: './server-element.component.html',
  styleUrls: ['./server-element.component.css']
})
export class ServerElementComponent implements OnInit {
//  @Input('srvElement') element: {type: string, name: string, content: string};    <--- This works

  @Input('srvElement') ele:Element;   <--- This doesn't work

  constructor() { }

  ngOnInit() { }

}        

This is my element class:

export class Element{
  type: string;
  name: string;
  content: string;
  constructor(type: string="", name: string="", content: string=""){
    this.type = type;
    this.name = name;
    this.content = content;
  }
}           

In parent class's html ie app.component.html, I have this(to communicate to child class):

<div class="container">
  <app-cockpit (notify)="onNotifyClicked($event)"></app-cockpit>
  <hr>
  <div class="row">
    <div class="col-xs-12">
      <app-server-element *ngFor="let serverElement of serverElements"
      [srvElement]="serverElement"></app-server-element>
    </div>
  </div>
</div>

Parent class ie app.component.ts:

import { Component } from '@angular/core';
import { Element } from './app.element';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  serverElements = [{type: 'server', name: 'Testserver', content: 'Just a test'}];
  element: {type: string, name: string, content: string};

  onNotifyClicked(e: Element){
    if(e.type==='server'){
        this.serverElements.push({
        type: 'server',
        name: e.name,
        content: e.content
      });
    } else {
        this.serverElements.push({
        type: 'blueprint',
        name: e.name,
        content: e.content
      });
    }
  }
}  

Can any one please explain to me why @Input('srvElement') ele:Element; doesn't work nor does @Input('srvElement') let ele=new Element(); (Passing my own custom object) but @Input('srvElement') element: {type: string, name: string, content: string}; just works fine??

I just found out that doing either of these two option works:

• @Input('srvElement') element=new Element();
• @Input('srvElement') element:Element;

NOTE: Object's name must be element as it has been used in child class's html ie server-element.component.html.