Living On The Edge Of DataMapper

DataMapper is organized into multiple gems that reside within 3 git repositories. At the very least you will need to clone the extlib and dm-core gems. If you plan to develop with a relational database, you will also need to install do. The dm-more project contains further optional gems that will make developing applications with DataMapper even easier.

Step 0 - Prerequisites

First, a couple of basic requirements before we begin. You will need to have an up-to-date installation of rubygems, the ruby package management system. To check what version you have, issue the following command:

gem --version

If that doesn’t give at least version 1.3.5, update your rubygems installation by running:

sudo gem update --system

Next, you’ll need git. It’s the source code management tool DataMapper uses. Its installation is left up to the reader, but here’s a few good resources to go to for help:

• Git - Fast Version Control System - Homepage
• Installing GIT on MAC OSX 10.5 Leopard
• Git On Windows
• Installing Git on Ubuntu

Step 1 - Gem dependencies

Once you have rubygems and git installed, you’ll need a few gems that datamapper depends on. To install them, run the following commands. Note that depending on your setup, you will possibly have to prepend sudo to some of the following commands (this applies to all the commands in this article).

gem install gemcutter
gem tumble
gem install rake rspec jeweler addressable

Step 2 - Install dm-core

Now that you have everything you need in place, it’s time to install the extlib and dm-core gems. To do that, prepare a directory where you will keep the sources, clone the git repositories, and install the contained gems with the provided rake tasks.

Prepare a directory where you will keep the git clones

mkdir -p ~/src/github/vendor

Change into that directory, clone the repositories and install the gems with the provided rake task.

cd ~/src/github/vendor
git clone git://github.com/datamapper/extlib.git
git clone git://github.com/datamapper/dm-core.git
cd extlib/
rake install
cd ..
cd dm-core/
rake install

Step 3 - Install do and dm-more (Optional)

With dm-core properly installed, you’re ready to install do and dm-more. The do project provides support for various relational databases and dm-more contains various gems that help you with common tasks you will face when developing database backed applications.

Installing a do adapter requires you to install data_objects as a minimum requirement. Additionally, you will need to install one or more specific database adapters that are provided within the project. The following shows you how to install data_objects and the do_mysql adapter. Replace do_mysql with whatever provided database adapter you need to work with.

cd ~/src/github/vendor
git clone git://github.com/datamapper/do.git
cd do/data_objects
rake install
cd ..
cd do_mysql
rake install

The dm-more project provides various gems that help you with common database development tasks. Clone the git repository, cd into the subdirectories that contain the gems you want to use, and rake install them from there. There is also a rake install task at the dm-more root directory which installs all of dm-more's gems. Unless you help with developing dm-more itself, you probably shouldn’t need to install all the gems that dm-more provides. The following instructions show how to clone the dm-more project and install the dm-validations gem.

cd ~/src/github/vendor
git clone git://github.com/datamapper/dm-more.git
cd dm-more/dm-validations
rake install

Keeping up with changes

Changes happen to DataMapper and it’s buddies all the time. To refresh your installation issue the following commands:

cd ~/src/github/vendor
cd extlib
git pull origin master
rake install
cd ../dm-core
git pull origin master
rake install
cd ../do
git pull origin master
cd data_objects
rake install
# cd into the desired adapter subdirectory and rake install from there
cd ../dm-more
git pull origin master
# cd into the desired gem subdirectory and rake install from there

Uninstall dm-core and friends

Should you ever have the need to uninstall datamapper completely, Dan Kubb has prepared a bash command that does the trick. Have a look at this gist for a oneliner that gets rid of datamapper completely.