1100 words, 4 mins
load和require的区别，gems和bundler以及rails autoload机制
load vs require
| load | require |
|---|---|
| each time will execute the code | only execute once |
| need to pass extension ‘.rb’ | no need to pass the extension |
| will check the file in the current directory | only search the $LOAD_PATH |
gems
- get the gem version
gem list eth
*** LOCAL GEMS ***
eth (0.4.12)
method_source (0.9.2)
- install the specific version
gem install domain_name -v 0.5.20160826
- find the gem location
gem which eth
/Users/gnuser/.rvm/gems/ruby-2.6.5/gems/eth-0.4.12/lib/eth.rb
bundler
bundle exec rspec will use the gem version specified in Gemfile.lock
Rails load all gems flow
config/boot.rb
ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../Gemfile', __dir__)
require 'bundler/setup' # Set up gems listed in the Gemfile
setup will read Gemfile.lock to call gem method for each gem with the correct version, if the gem version mismatched will raise an exception.
application.rb
# Require the gems listed in Gemfile, including any gems
# you've limited to :test, :development, or :production.
Bundler.require(:default, Rails.env)
call kernel.require for each gem.
require: false in Gemfile meaning
by default, Bundler.require will require every gem from Gemfile. if we use require: false, you can explictly require the gem when you want to use it.