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<h1>Example: Request JSON using Yahoo! Pipes</h1>
<div class="yui3-g">
<div class="yui3-u-3-4">
<div id="main">
<div class="content"><style type="text/css" scoped>
#output li {margin-left:2em;}
#output { background-color:#FFFFFF; border:1px dotted #666666; padding:1em; margin-top:1em;}
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<div class="intro">
<p>In the example below, IO is employed to make a cross-domain request to <a href="http://pipes.yahoo.com">Yahoo! Pipes</a>. The output of the Pipe is an RSS-style feed formatted as JSON. We pass that output to the JSON Utility's <code>parse</code> method for sanitization and then display the contents of the Pipe in a list.</p>
<p>This example demonstrates how IO can use the Cross-Origin Resource Sharing (http://www.w3.org/TR/cors/) mechanism for making cross-domain requests.</p>
<p><strong>Please note: </strong> All the browsers listed in the Browser Test Baseline (http://developer.yahoo.com/yui/articles/gbs/) support CORS with the exception of IE 6.0 and IE 7.0, and Webkit on iOS 3. In addition to browser capability, the requested resource must respond with the proper Access-Control headers for the request to succeed.</p>
</div>
<div class="example">
<button id="pipes">Load RSS news feed from Yahoo! Pipes.</button>
<div id="output">
<ul>
<li>Content from Yahoo! Pipes feed will display here.</li>
</ul>
</div>
<script language="javascript">
YUI({ filter:'raw' }).use("io-xdr", "json-parse", "node",
function(Y) {
//Data fetched will be displayed in a UL in the
//element #output:
var output = Y.one("#output ul");
//Event handler called when the transaction begins:
var handleStart = function(id, a) {
Y.log("io:start firing.", "info", "example");
output.set("innerHTML", "<li>Loading news stories via Yahoo! Pipes feed...</li>");
}
//Event handler for the success event -- use this handler to write the fetched
//RSS items to the page.
var handleSuccess = function(id, o, a) {
//We use JSON.parse to sanitize the JSON (as opposed to simply performing an
//JavaScript eval of the data):
var oRSS = Y.JSON.parse(o.responseText);
//From here, we simply access the JSON data from where it's provided
//in the Yahoo! Pipes output:
if (oRSS && oRSS.count) {
var s = "<!--begin news stories fetched via Yahoo! Pipes-->",
//t in this case is our simple template; this is fed to
//Y.Lang.sub() as we loop through RSS items:
t = "<li><a href='{link}'>{title}</a>, {pubDate}</li>";
for (var i=0; i<oRSS.count; i++) {
s += Y.Lang.sub(t, oRSS.value.items[i]);
}
//Output the string to the page:
output.set("innerHTML", s);
output.addClass("yui-null");
} else {
//No news stories were found in the feed.
var s = "<li>The RSS feed did not return any items.</li>";
}
}
//In the event that the HTTP status returned does not resolve to,
//HTTP 2xx, a failure is reported and this function is called:
var handleFailure = function(id, o, a) {
Y.log("ERROR " + id + " " + a, "info", "example");
}
//With all the apparatus in place, we can now configure our
//IO call. The method property is defined, but if omitted,
//IO will default to HTTP GET.
var cfg = {
method: "GET",
xdr: {
use:'native'
},
on: {
//Our event handlers previously defined:
start: handleStart,
success: handleSuccess,
failure: handleFailure
}
};
//Wire the button to a click handler to fire our request each
//time the button is clicked:
var handleClick = function(o) {
Y.log("Click detected; beginning io request to Yahoo! Pipes.", "info", "example");
// Remove the default "X-Requested-With" header as this will
// prevent the request from succeeding; the Pipes
// resource will not accept user-defined HTTP headers.
Y.io.header('X-Requested-With');
var obj = Y.io(
//this is a specific Pipes feed, populated with cycling news:
"http://pipes.yahooapis.com/pipes/pipe.run?_id=giWz8Vc33BG6rQEQo_NLYQ&_render=json",
cfg
);
}
//add the click handler to the Load button.
Y.on("click", handleClick, "#pipes");
}
);
</script>
</div>
<h3 class="first">Implementing a Cross-Domain Request for JSON Data</h3>
<p>In this example, we begin with a YUI instance that loads the <code>io-xdr</code>, <code>json-parse</code>, and <code>node</code> modules. The <code>io-xdr</code> module is the key module. The other modules are used to process and output the results:</p>
<pre class="code prettyprint">//Create a YUI instance including support for IO and JSON modules:
YUI().use("io-xdr", "json-parse", "node", function(Y) {
// Y is the YUI instance.
// The rest of the following code is encapsulated in this
// anonymous function.
});</pre>
<p>We'll also get a Node reference to the container we'll be using to output the data we retrieve:</p>
<pre class="code prettyprint">//element #output:
var output = Y.one("#output ul");</pre>
<p>handleSuccess is the function responsible for handling the response data. The first thing we do is sanitize the data to ensure we have valid JSON.</p>
<pre class="code prettyprint">var oRSS = Y.JSON.parse(o.responseText);</pre>
<p>Next, we create a simple markup template and use <code>Y.Lang.sub()</code> to fill in the data, as we iterate through the JSON and output the results.</p>
<pre class="code prettyprint">//From here, we simply access the JSON data from where it's provided
//in the Yahoo! Pipes output:
if (oRSS && oRSS.count) {
var s = "<!--begin news stories fetched via Yahoo! Pipes-->",
//t in this case is our simple template; this is fed to
//Y.Lang.sub() as we loop through RSS items:
t = "<li><a href='{link}'>{title}</a>, {pubDate}</li>";
for (var i=0; i<oRSS.count; i++) {
s += Y.Lang.sub(t, oRSS.value.items[i]);
}
//Output the string to the page:
output.set("innerHTML", s);
output.addClass("yui-null");
}</pre>
<p>Create the configuration object for the cross-domain request, setting up the event handlers and instructing IO to use the browser's native cross-domain transport.</p>
<pre class="code prettyprint">var cfg = {
method: "GET", //If omitted, the default is HTTP GET.
xdr: {
use:'native'//For browsers that support CORS.
},
on: {
//Our event handlers previously defined:
start: handleStart,
success: handleSuccess,
failure: handleFailure
}
};</pre>
<p>Create an event handler that will make the IO call to Yahoo! Pipes when the Load button is clicked:</p>
<pre class="code prettyprint">//Wire the button to a click handler to fire our request each
//time the button is clicked:
var handleClick = function(o) {
Y.log("Click detected; beginning io request to Yahoo! Pipes.", "info", "example");
// Remove the default "X-Requested-With" header as this will
// prevent the request from succeeding; the Pipes
// resource will not accept user-defined HTTP headers.
Y.io.header('X-Requested-With');
var obj = Y.io(
//this is a specific Pipes feed, populated with cycling news:
"http://pipes.yahooapis.com/pipes/pipe.run?_id=giWz8Vc33BG6rQEQo_NLYQ&_render=json",
cfg
);
}
//add the click handler to the Load button.
Y.on("click", handleClick, "#pipes");</pre>
<h4>Full Script</h4>
<p>The full script source for this example is as follows:</p>
<pre class="code prettyprint"><button id="pipes">Load RSS news feed from Yahoo! Pipes.</button>
<div id="output">
<ul>
<li>Content from Yahoo! Pipes feed will display here.</li>
</ul>
</div>
<script language="javascript">
YUI({ filter:'raw' }).use("io-xdr", "json-parse", "node",
function(Y) {
//Data fetched will be displayed in a UL in the
//element #output:
var output = Y.one("#output ul");
//Event handler called when the transaction begins:
var handleStart = function(id, a) {
Y.log("io:start firing.", "info", "example");
output.set("innerHTML", "<li>Loading news stories via Yahoo! Pipes feed...</li>");
}
//Event handler for the success event -- use this handler to write the fetched
//RSS items to the page.
var handleSuccess = function(id, o, a) {
//We use JSON.parse to sanitize the JSON (as opposed to simply performing an
//JavaScript eval of the data):
var oRSS = Y.JSON.parse(o.responseText);
//From here, we simply access the JSON data from where it's provided
//in the Yahoo! Pipes output:
if (oRSS && oRSS.count) {
var s = "<!--begin news stories fetched via Yahoo! Pipes-->",
//t in this case is our simple template; this is fed to
//Y.Lang.sub() as we loop through RSS items:
t = "<li><a href='{link}'>{title}</a>, {pubDate}</li>";
for (var i=0; i<oRSS.count; i++) {
s += Y.Lang.sub(t, oRSS.value.items[i]);
}
//Output the string to the page:
output.set("innerHTML", s);
output.addClass("yui-null");
} else {
//No news stories were found in the feed.
var s = "<li>The RSS feed did not return any items.</li>";
}
}
//In the event that the HTTP status returned does not resolve to,
//HTTP 2xx, a failure is reported and this function is called:
var handleFailure = function(id, o, a) {
Y.log("ERROR " + id + " " + a, "info", "example");
}
//With all the apparatus in place, we can now configure our
//IO call. The method property is defined, but if omitted,
//IO will default to HTTP GET.
var cfg = {
method: "GET",
xdr: {
use:'native'
},
on: {
//Our event handlers previously defined:
start: handleStart,
success: handleSuccess,
failure: handleFailure
}
};
//Wire the button to a click handler to fire our request each
//time the button is clicked:
var handleClick = function(o) {
Y.log("Click detected; beginning io request to Yahoo! Pipes.", "info", "example");
// Remove the default "X-Requested-With" header as this will
// prevent the request from succeeding; the Pipes
// resource will not accept user-defined HTTP headers.
Y.io.header('X-Requested-With');
var obj = Y.io(
//this is a specific Pipes feed, populated with cycling news:
"http://pipes.yahooapis.com/pipes/pipe.run?_id=giWz8Vc33BG6rQEQo_NLYQ&_render=json",
cfg
);
}
//add the click handler to the Load button.
Y.on("click", handleClick, "#pipes");
}
);
</script></pre>
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<div class="hd">
<h2 class="no-toc">Examples</h2>
</div>
<div class="bd">
<ul class="examples">
<li data-description="Use IO to request data over HTTP.">
<a href="get.html">HTTP GET to request data</a>
</li>
<li data-description="Use IO to request XML data from a remote web service.">
<a href="weather.html">Request XML data from Yahoo! Weather</a>
</li>
<li data-description="Use IO to make a cross-domain request to Yahoo! Pipes, returning data from disparate sources.">
<a href="xdr.html">Request JSON using Yahoo! Pipes</a>
</li>
</ul>
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<h2 class="no-toc">Examples That Use This Component</h2>
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<ul class="examples">
<li data-description="Shows how to create a simple plugin to retrieve content for the Overlay using the io utility.">
<a href="../overlay/overlay-io-plugin.html">IO Plugin</a>
</li>
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