title: How to create a custom form component by extending BaseInput in ionic2
body: <p>I want to create a custom form input component in ionic2, by extending <code>BaseInput</code>. But it doesn't rendered, and I can't find it on the DOM.</p>
  
  <pre><code>import { Component, ElementRef, OnDestroy, Optional, Renderer, 
  ViewEncapsulation } from "@angular/core";
  import { Config, Form, Item } from "ionic-angular";
  import { BaseInput } from "ionic-angular/util/base-input";
  import { NG_VALUE_ACCESSOR } from "@angular/forms";
  
  @Component({
    selector: 'my-checkbox',
    template:
    '&lt;p&gt;aaaaa&lt;/p&gt;',
    host: {
      '[class.checkbox-disabled]': '_disabled'
    },
    providers: [ { provide: NG_VALUE_ACCESSOR, useExisting: MyCheckboxComponent, multi: true } ],
    encapsulation: ViewEncapsulation.None,
  })
  export class MyCheckboxComponent extends BaseInput&lt;any&gt; implements OnDestroy {
  
    constructor(form: Form, config: Config, elementRef: ElementRef, renderer: Renderer, @Optional() item: Item) {
      super(config, elementRef, renderer, 'my-checkbox', [], form, item, null);
    }
  
  }
  </code></pre>
  
  <p>The code is copy from <code>src/component/checkbox/checkbox.ts</code> and make a little changes.</p>