polymer - Iron-ajax Data binding -

how data bind in new polymer v1.0?

i saw answer in polymer iron-ajax : how bind data input element iron-ajax's body attribute

but did not me , here 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 correct log in console json string, when value being returned, value taken literally (same problem told in link provided above) , not value.

i error in console bad request code 400. highly appreciated.

the property params of type object. unlike in linked example, can return native object.

processparams: function(part1, qry, maxresults1, key1) {     return {         part: part1,         q: qry,         maxresults: maxresults1,         key:key1     }; }