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Archive for ‘Programming’

FXRuby – How to capture close on the main window

I wrote a small FXRuby program which allows the user to do some simple file manipulation, then upload the altered files via FTP to a web server.

I ran into a small problem in that when the user clicked the “Close” button (the X in the upper right-hand corner) of the main window, the application closed straight away.

Normally, this would be the desired behaviour, but in this case I wanted to intercept this message and do some application cleanup first (delete temporary files, make sure the user had saved their work etc).

Here’s how I did it.

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How to install rbenv on Linux Mint 16

Last year I switched from Windows to Linux Mint as my main operating system and wanted to install a Ruby version manager.

I weighed up the pros and cons of what was available and eventually opted for rbenv as it seemed more lightweight, would let me compile my Rubies myself and (in contrast to RVM) didn’t come with any way of managing gems.

I searched Google and came up with a couple of tutorials to follow, such as this one and this one which described how to install rbenv, but unfortunately they didn’t work for me.

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How to persist checkbox checked state after page reload

This quick tip describes how to have your browser remember the state of checkboxes once a page has been refreshed or a user navigates away from your site to come back at a later date.

It might be useful to Persist Checkbox Checked State if, for example, you use checkboxes to allow your users to set site-specific preferences, such as opening external links in a new window or hiding certain page elements.

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Setting a fallback font in Prawn

At work, one of the applicants to our programme submitted parts of her application in Russian (despite it being an English speaking programme).

The database could handle this fine, as it stores entries using the UTF-8 character set, but the PDF generation part of our application refused to cooperate (just displaying a bunch of underscores). 

We use the Prawn library to generate our PDFs, so I set about finding a way to make Prawn play nice with the Cyrillic characters.

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Trouble installing mysql2 gem on Windows 8 with Ruby2

I recently installed the 64 bit version of Ruby 2.0 on my Windows 8 machine.

All of my old projects I tested with it ran just fine and the world was a happy place.

Then I had to install Rails, so that I could make some minor changes to an existing app … and the pain began.

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How to center an HTML Element using JavaScript

Imagine you have an element which is dynamically added to your web page (an image in a lightbox, for instance) and you want to centre it on the screen both horizontally and vertically.

You could do so with CSS (as this article explains), but if you don’t know the dimensions of the element you want to centre or you need to support older browsers, things can become quite tricky quite quickly.

That’s when you should think about doing the job with JavaScript.

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Use AJAX to filter MySQL results set

I recently helped someone with a project where they had to select a bunch of records from a database, then on the client side use AJAX to filter those records according to certain criteria.

This was a fun thing to work on and a good opportunity to demonstrate the power of AJAX, so I thought I’d write it all up in the form of a quick tutorial.

For the impatient among you, here’s a demo of what we’ll end up with.

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How to restore a previously deleted file from a GIT repository

I was recently working on a project and realised that I needed a file that I had long since deleted.

On the one hand, this wasn’t very tragic as I had the project under version control using GIT. However, finding the exact command to restore a single file from a rather old commit proved to be a little more difficult, so I thought I’d make note of it here.

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Making a jQuery plugin – 101

The other day my colleague mentioned that she’d like a simple calendar on the front page of her website. This didn’t sound too difficult, so being a nice chap I said I’d take a look.

Unfortunately, it turned out that my colleague works with this rather rigid content management system and beyond a few pre-defined widgets, she didn’t have the ability to alter much on the page.

On closer inspection however, I found that one of these widgets allowed us to create arbitrary HTML elements, as well as to include script tags. This sounded like a perfect case for a jQuery plugin … Read more…

Prevent double data submission in Rails 3

I was recently working on an application, that lets people from all over the world apply for a programme at the university I work at.

The application works well and does what it should, but we were seeing quite a lot of double submissions, that is to say, the same person applying multiple times in short succession.

Here’s how I fixed that.

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