Christian Engvall

When following the instructions to install cocoapods the following error occured:

Building native extensions.  This could take a while…

ERROR:  Error installing cocoapods: ERROR: Failed to build gem native extension.

Command line tools

The solution was to install the command line tools with this command:

xcode-select –install

and then again run: sudo gem install cocoapods

Sometimes we may need to undo a git stash apply, maybe we didn’t mean to apply it at all or we just applied it to the wrong branch.

Update: I’ve made an easy extension to git that makes this command more easy to remember, i call it gitUndo. With that extension all you need run is: git undo stash-apply.

Git stash commands

To un-apply the most recent stash this command is used:

git stash show -p | git apply -R

now to add this as an alias we run this command in the terminal:

git config --global alias.stash-unapply '!git stash show -p | git apply -R'

Now when un-applying is needed we will be able to run:

git stash-unapply

I keep forgetting how to undo a commit with git because i very rarely need it. But i figured if i aliased it to git undo i wouldn’t need to google the command every time. Now how does one do that? It turned out to be pretty simple actually.

Update: I’ve made an easy extension to git that makes this command more easy to remember, i call it gitUndo. With that extension all you need run is: git undo commit.

Git reset

The command to undo a commit and reset to the commit before HEAD and keeping the changes is:

git reset --soft HEAD^

And to add this as an alias to the .gitconfig file use this command:

git config --global alias.undo 'reset --soft HEAD^'

Now when running git undo in the terminal your commit will be reset.

When using a default namespaced xml an xpath-expression need to look a bit different than when the xml uses namespace prefixes. Lets have a look at this namespaced XML:

<?xml version="1.0"?>
<bk:bookstore xmlns:bk="urn:xmlns:25hoursaday-com:bookstore">
 <bk:book>
    <bk:title>Lord of the Rings</bk:title>
    <bk:author>J.R.R. Tolkien</bk:author>
 </bk:book>
</bk:bookstore>

The xpath used to get the title of the book would look like: /bk:bookstore/bk:book/bk:title

Now lets look at this default namespaced XML, it has no prefixes so we need to take another aproach to get the title of the book this time:

<?xml version="1.0"?>
<bookstore xmlns="urn:xmlns:25hoursaday-com:bookstore">
 <book>
    <title>Lord of the Rings</title>
    <author>J.R.R. Tolkien</author>
 </book>
</bookstore>

This time the xpath would look like: _/[local-name()=’bookstore’]/[local-name()=’book’]/*[local-name()=’title’] _The xpath matches any namespace and looks for the local name bookstore and after that book and title.

PHP Example

The following code shows how to use it, and the code including the xml files can be downloaded from github.

<?php
  $xml = simplexml_load_file('namespaced.xml');
	$result = $xml->xpath('/bk:bookstore/bk:book/bk:title');
	echo $result[0];
	echo "<br />";
	$xml = simplexml_load_file('default-namespaced.xml');
	$result_from_default_namespace = $xml->xpath("/*[local-name()='bookstore']/*[local-name()='book']/*[local-name()='title']");
	echo $result_from_default_namespace[0];

I recently released Husvisningar.se with my friends Simon and Jacob. It has been, and is continuing to be a really fun project. We decided to use Ruby on rails for this, just to learn something new.

Ruby on rails is an open source mvc-framework that is used to build web applications with, some famous sites using it are Github and Twitter. According to it’s creator, David Heinemeier Hansson, the framework is optimized for programmer happiness and beautiful code. But this wasn’t the only good thing about it. There are tons of gems out there making it faster to create a site, and in almost every case there is someone else who has solved what you are trying to implement and shared the code. So I thought i’d share some good gems that we’ve used on our site.

Gems used on Husvisningar

Asset sync This gem syncs images, css and javascript assets to S3. This helps to load assets faster when serving them from a cookieless domain. 

Chronic Chronic is a natural language date/time parser. So to get the date for next tuesday at 5 you can use Chronic this way:

Chronic.parse(‘this tuesday 5:00’) #=> Tue Aug 29 17:00:00

Stringex Stringex adds some useful extensions to the string class of ruby. For example it helps to remove unwanted chars when converting a string to use in a url.

“simple English”.to_url => “simple-english”

aws-sdk This gem is the official gem for amazon web services. Can be used for example if asset sync doesn’t fit your needs all the way.

MiniMagick A lightweight alternative to RMagick to scale images with ImageMagick. Using it is as simple as this:

image = MiniMagick::Image.open(“input.jpg”) image.resize “100x100” image.write “output.jpg”

RailsConfig RailsConfig helps you easily manage environment specific Rails settings in an easy and usable manner.

time_diff Gem which calculates the difference between two dates and returns a hash of time difference in terms of years, month, week, day, hour, minute and second.

Dalli Dalli is a high performance pure Ruby client for accessing memcached servers.