Using nvm to manage multiple active node.js versions

Today I had to install a different version of node.js on my laptop, because the program I wanted to try required a newer version than the one I had.

After googling a bit, I found nvm developed by Tim Caswell. It is a "simple bash script to manage multiple active node.js versions", (nvm stands for Node Version Manager). It helped me to quickly solve my problem.

I followed the installion instructions and in 3 steps I had the last version of node (v0.8.18) up and running.

This is what I did:

First I show you the very old version that was installed on my laptop for a previous pet project:

$ node --version
v0.5.11-pre

I cloned nvm repository from GitHub:

$ git clone git://github.com/creationix/nvm.git ~/.nvm
Initialized empty Git repository in /home/bscuser/.nvm/.git/
remote: Counting objects: 557, done.
remote: Compressing objects: 100% (327/327), done.
remote: Total 557 (delta 290), reused 471 (delta 219)
Receiving objects: 100% (557/557), 76.33 KiB | 8 KiB/s, done.
Resolving deltas: 100% (290/290), done.

And followed Tim's instructions by, first, sourcing the nvm.sh script

$ . ~/.nvm/nvm.sh

and then using nvm to install the current version of node

$ nvm install v0.8.18
######################################################################## 100,0%
Now using node v0.8.18

Once it finished, the node version was:

$ node --version
v0.8.18

As I plan to be using the program that needed this newer version of node for a while, I added the following lines to my .bashrc file:

. ~/.nvm/nvm.sh
nvm use v0.8.18

so I have the v0.8.18 version every time I open a console.

nvm has many other useful options that I plan to use. Thank you very much Tim for sharing it.

Interesting Talk: "Chasing the Golden GOOS"

I've just watched this interesting talk by Alex Aitken and Nick Faulkner:

• Chasing the Golden GOOS

They talk about what they learned while developing a HTML5 application following the principles from Growing Object-Oriented Software Guided by Tests.

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How to access the first element of an Json::Value array

To access the first element of an Json::Value array the following code may not work:

...
double x = point[0].asDouble()
...

Instead you have to write:

...
double x = point[0u].asDouble()
...

To find out why just check the following fragment of the Json::Value documentation:

const Value & operator[] (int index) const
Access an array element (zero based index)
You may need to say 'value[0u]' to get your compiler to distinguish this from the operator[] which takes a string.

How to move files or directories in Subversion without losing their history

Sometimes we need to move files or directories in our code to a better location.

So far, we were doing it using the Move option in Eclipse.

However, this was wrong, let's see why:

Our code is under Subversion, a version control system.
The way we were moving things was interpreted by Subversion as if we had deleted them and the added new ones. That means that all the history of the moved item is lost and that's not what we intended.

To keep the history of the item when moving it, we must use Subversion to move it.

This is how it's done from the console:

$ svn move source destiny

This command moves the file/directory in your working copy or in the repository keeping its history. It's equivalent to an svn copy followed by svn delete.
The only limitation is that you can only move files within a single repository and the destiny must be a working copy, that is, it must be already included in your repository (to know more).

So from now on, anytime we want to move files or directories in our code to a new location, we'll use svn move.