了解Gemfile（Rails）：如果已经包含“宝石'mongo'”，则不需要“需要mongo”吗？

Question

This is our Gemfile.

Is the line require mongo redundant since gem 'mongo' is already included?

If not, what is the purpose of require mongo ?

We're on Rails 3.

Thanks!

source 'http://rubygems.org'

require 'rubygems'
require 'mongo'

gem 'rails', '3.0.6'
gem 'mongo'
gem 'mongo_mapper'
gem 'fastercsv'

# Bundle edge Rails instead:
# gem 'rails', :git => 'git://github.com/rails/rails.git'

#gem 'sqlite3'
gem 'mysql'
gem 'whois'

Answer 1

You shouldn't put require statements in your Gemfile. This is also true for the require 'rubygems' on the line before.

What require does, is what it always does: load the gem. The Gemfile is loaded when you run bundle install . If you try to load a gem before bundle install has run, the gem might not be installed yet.

Gems specified in your Gemfile are required by Rails by default too, by the way.