Quote of the Day

You should see over these lines the result of my last project: a Quote of the Day implementation for Blogger It should be a piece of cake to port to other blogging platforms: the only requirement for the code to work is to have a recent version of the JQuery Javascript library loaded. Rewriting the code to eliminate that dependency should also be easy. Quips are published on Google Spreadsheets.

[Warning! Buzzword-enabled text ahead!] GData APIs implement an Atom extension that enables remote document querying and editing. What’s more, query results can be obtained as evaluated JSON objects; this technique allows to bypass most cross-site scripting security constraints, so Ajax widgets can be implemented without control over the server side.

We will need a published spreadsheet sporting quips and authors in two columns.

A tiny little script will get us the sheet’s contents. We only have to look for these pieces of information in order to make it work:

  • Publishing key.
  • Unique identifier for the desired sheet (a spreadsheet is organized as a book, so it can contain several sheets).
  • Desired cell range.

These can be obtained from the feed publishing URL that appears in Publish/More publishing options in the Google Spreadsheets interface. There goes the script:

var CiteSpreadsheet = {
    'rows': 159,
    'getJsonUrl': function(idx) {
        var baseSpreadsheet = 'http://spreadsheets.google.com/feeds/';
        var feedType = 'cells/';
        var key = 'o06661241339204957995.1659223542184495700/';
        var sheetId = 'od6/';
        var feedAccess = 'public/basic?';
        var range = 'range=A' + idx + ":B" + idx;
        var output = '&alt=json-in-script';
        var callback = '&callback=CiteSpreadsheet.processJsonResponse';
        return baseSpreadsheet + feedType + key + sheetId + feedAccess + range + output + callback;
    },
    'createScriptElem': function(url) {
        var html = '<script type="text/javascript" src="' + url + '"></script>';
        $(html).appendTo('body');
    },
    'getIndex': function() {
        var today = new Date();
        var startDate = new Date(today.getYear(), 0, 1);
        var delta = today.getTime() - startDate.getTime();
        var dayOfYear = Math.ceil(delta / 86400000);
        return dayOfYear % CiteSpreadsheet.rows;
    },
    'processJsonResponse': function(jsonData) {
        var retrievedContent = "<span>" + jsonData.feed.entry[0].content.$t +
            " <cite>" + jsonData.feed.entry[1].content.$t + "</cite></span>";
        $(".cite").append(retrievedContent);
    }
};

CiteSpreadsheet.createScriptElem(
    CiteSpreadsheet.getJsonUrl(
        CiteSpreadsheet.getIndex()));

What the code does, in short, is dynamically inserting a <script> tag in the document, with its src attribute pointing to a specific query URL for the spreadsheet. Output format should be json-in-script; this returns a ready-to-execute script that wraps data in a Javascript object. Its general format is described in the previous link, but Firefox, Firebug and a judicious break point go all the way to get a hold on the gory details.

We’ve got a feed with information about certain cells (range An:Bn, where n is a row index). As the sheet contains 159 quotations, in order to provide a different one daily we compute that row index as the current day in year modulus total number of rows.

Last but not least, we need a hook; someplace in the blog template to anchor the newly retrieved content. We do so by adding to the template an HTML/Javascript module where we want our quip to appear. Its contents should be, at the very least,

<span class="cite"/>

(a <div> would also work —in fact, any container element with class cite). For other blogging platforms the same effect could be achieved by directly editing the template, or by some other means which I leave as exercise for the reader.

Publicado por

Iván Rivera

Another instance of Homo sapiens.