每天一剂Rails良药之Creating Your Own Rake Tasks

Ruby的Rake工具其实是模仿的Make，我们写一个简单的Rakefile看看:
[code]
desc "Rake Test"
task :main
puts "Hello, Rake!"

task :default => :main
[/code]
然后我们在Rakefile当前目录运行[b]rake[/b]或[b]rake -f Rakefile[/b]即可
其中我们定义了一个main task，并且将其设为默认task
我们再看看怎样写结合Rails的Rakefile,Rails在lib/tasks目录里查找并加载所有以.rake作为后缀名的Rakefile，如lib/tasks/load_musicians.rake:
[code]
desc "Load musicians and the instruments they play into the database."
task :load_musicians => ['musicians.csv', :environment] do |t|
before_count = Musicians.count
File.read(t.prerequisites.first).each do |line|
given_name, surname, instrument = line.split(/,/)
Musician.create(:given_name => given_name,
:surname => surname,
:instrument => instrument)
end
puts "Loaded #{Musicians.count - before_count} musicians."
end
[/code]
然后我们可以运行[b]rake load_musicians[/b]命令来调用load_musicians task
该task的dependency列表中包含:environment，这是用来初始化Rails环境以及建立数据库连接
如果我们自定义的task需要migrate，则我们可以这样写:
[code]
task :load_musicians => ['musicians.csv', :migrate] do |t|
[/code]
则我们运行该task时会先rake db:migrate，而且:migrate已经初始化了Rails环境，我们不用再写:environment了