Iron-ajax Data binding

Question

How to data bind in the new Polymer v1.0?

I saw an answer in polymer iron-ajax : How to Bind data from input element to iron-ajax's body attribute

But it did not help me and Here is my code

<dom-element id="test-app> 
<template>
...
<iron-ajax
auto
url="https://www.googleapis.com/youtube/v3/search"
params="{{ajaxParams}}"
handleAs="json" lastResponse="{{response}}"
method='GET'>
</iron-ajax>
</template>
</dom-module>

Script

Polymer({
        is:"Test-app",

        properties: {
            qry: {
                type: String,
                value: 'Cat'
            },
            key1: {
                type: String,
                value: 'myapikey'
            },
            part1: {
                type: String,
                value: 'snippet'
            },
            maxResults1: {
                type: Number,
                value: 10
            },
            ajaxParams: {
                type: String,
                computed: 'processParams(part1, qry, maxResults1, key1)'
            }
        },
        processParams: function(part1, qry, maxResults1, key1){
            var param = JSON.stringify({part: part1, q:qry, maxResults: maxResults1, key:key1});
            console.log(param);
            return param;
        }
    });
</script>

I get the correct log in console as a JSON string, but when this value is being returned, the value is taken literally (same problem as told in the link provided above) and not as its value.

I get an error in console as bad request code 400. Any help is highly appreciated.

Answer 1

The property params is of type Object. Unlike in the linked example, you can just return a native object.

processParams: function(part1, qry, maxResults1, key1) {
    return {
        part: part1,
        q: qry,
        maxResults: maxResults1,
        key:key1
    };
}

Answer 2

 <template is="dom-bind" id="app">
  <iron-ajax auto
      url="https://www.googleapis.com/youtube/v3/search"
      params='{"part":"snippet", "q":"polymer", "key": "AIzaSyAuecFZ9xJXbGDkQYWBmYrtzOGJD-iDIgI", "type": "video"}'
      handle-as="json"
      last-response="{{ajaxResponse}}"></iron-ajax>

    <template is="dom-repeat" items="[[ajaxResponse.items]]">
      <div class="horizontal-section">
        <h2><a href="[[url(item.id.videoId)]]" target="_blank">[[item.snippet.title]]</a></h2>
        <iron-image src="[[item.snippet.thumbnails.high.url]]" width="256" height="256" sizing="cover" preload fade></iron-image>
        <p>[[item.snippet.description]]</p>
      </div>
    </template>
<script>
var app = document.querySelector('#app');

app.url = function (videoId) {
  return 'https://www.youtube.com/watch?v=' + videoId;
};
</script>

I'm sorry. the ajax query returns a json array of Youtube videos with the paramaters listed in the property "params". the one way binding "[[ajaxResponse.items]]" binds the response to the repeating template "dom-repeat". the url function just appends the videoId to the individual links. I copied the code straight from the iron-ajax demo that ships with polymer starter kit