title: How to convert a promise to an observable?
body: <p>I am working on ionic 2 project. I am able to return all contacts in the device/phone. But I used the promise code which has very slow performance because of single request at a time. Now, I want change that promise code to an observable. Please help me to solve this.</p>
  
  <pre><code>findContact(searchKey){
      if(searchKey.target.value == "" || searchKey.target.value == undefined || searchKey.target.value == null){
          this.contactSelected = false;
      } else{
          this.contactSelected = true;
      }
      let options = {
          multiple: true,
          hasPhoneNumber: true,
          filter: searchKey.target.value
      }
      let cantactFields = ['displayName', 'phoneNumbers'];
      Contacts.find(cantactFields, options).then(res =&gt; {
              this.contactResults = res;
      }, (er) =&gt; {
          console.log(er);
      })
  }
  </code></pre>
  
  <p><code>Contacts.find()</code> is the method where I used the promises. And this method returns the contacts very slowly.</p>