I have seen an example, and I am trying to reproduce it. The `name` and `age` are declared inside the `class` and `services` ( Injectable ) added in the `constructor`.

I'd like to know the difference between declaring variable with `class` and `constructor` here. Any one help me to know the differences.

As well instead of declaring the `name` and `age` can't I declare inside of the `constructor` itself?

here is my code :

```
    import {Component} from 'angular2/core';
    import {CommonService} from './commonService';
    import {commonServiceIndipendent} from './commonSerivceIndipendent';

    @Component({

      selector : 'component1',

      template : `

        <h1>Component 1</h1>
        <input type="text" #message />

        <button (click)="onLog(message.value)" >Component1 - Message </button>

      `,

      providers:[commonServiceIndipendent]

    })

    export class Component1 {

      name:string; //why here?
      age:number; //why here?

//can't i add to constructor? if so how?
      constructor ( 
        private _commonService : CommonService, 
        private _commonServiceIndipendent:commonServiceIndipendent) {}

      //sending to same service. it has other instance in history
      onLog(message:string) {

        this._commonService.log( message );

        this.name = "Arif",
        this.age = 20;

        this.onData();

      }

      onData() {
        this._commonServiceIndipendent.myData(this.name,this.age);
      }

    }

```