Building my first directive with angular2

Recently i started to play with recently released beta of angular2.
I'm totally beginner and i want to build very simple thing.
I want to build the component (component is like directive in angular 1.) that displays current time in format given as a parameter (through the attribute format).

  
  
    <now format="'h:mm:ss'"></now>
  

When rendered HTML, should look like this:

How to run angular2?

First thing you need then you want to run angular2 is environment.
You can use one of angular2 starter kits like this one Or just open plunker and select "Editor" -> "New" -> "AngularJs" -> "2.0.x TS" and viola!! you are angular2 programmer!

Component

The first basic thing in angular2 is component, so: Lets create a component:

import {Component} from 'angular2/core'

@Component({
  selector: 'now',
  template: `
{{date}}
`      
})
export class Now {
  private date;
  constructor() { 
    this.date =  new Date(); 
  } 
} 

Yoo hoo!!! The component created and running!!!
And it displays the current date!!!
But one little disturbing thing is that date appears raw , which is little bit ugly...

So lets improve the component by formatting the output.

Pipe (Filter)

Like in sngular 1. there are filters in angular2, they called pipes

import {Component} from 'angular2/core'

@Component({
  selector: 'now',
  template: `
{{date | date :'dd/MM/yyyy'}}
`      
})

Getting value from attribute (The tricky part)

As we already said the desired format should be passed through the attribute. But how to access this attribute from inside component constructor? Fortunately there is Attribute module which enables you to inject attribute into constructor parameters:

import {Component, Attribute} from 'angular2/core'
export class Now {
   private date;
   
  constructor(@Attribute("format") format) { 
    this.format = format;
    this.date =  new Date(); 

  } 

} 

Better way

After Lenin's older brother was executed because he tried(but failed) to kill king of Russia with bomb, young Lenin said "We will go different way"...
After looking at angular2 docs i found better (more angular2mish) way which says that if we want to pass attribute to component we must use square brackets :

  
  
    <now [format]="'h:mm:ss'"></now>
  

I will use @Input module instead of @attribute

import {Component,  Input} from 'angular2/core'

@Component({
  selector: 'now',
  template: `
      
{{date | date: _format}}
    `
})
export class Now {
   private date;
   @Input() set format(formatName:string){
     this._format = formatName;
   
   }   
  constructor() { 
    this.date =  new Date(); 
  } 

} 

How to update time each second?

Little nice thing to add here is ability to update the time displayed in directive each second. For achieve this i'm using ES6 fat arrow syntax

export class Now {
   private date;
   @Input() set format(formatName:string){
     this._format = formatName;
   
   }   
  constructor() { 
    this.date =  new Date(); 
    
    setInterval(() => {
        this.date =  new Date();
     }, 1000);
  } 

} 

View it on plunker: