尾随冒号在Rake任务名称中的含义是什么？

Question

In the custom Rake task example:

desc "I am short, but comprehensive description for my cool task"
task task_name: [:prerequisite_task, :another_task_we_depend_on] do
  # All your magic here
  # Any valid Ruby code is allowed
end

What does the colon suffix after task_name indicate? Normally, the task name is a symbol - what's different about this if you have prerequisites?

Answer 1

The literal {task_name: [:symbol]} is a shorthand notation for {:task_name => [:symbol]} , this notation was introduced with Ruby 1.9:

{task_name: [:symbol]}
# => {:task_name=>[:symbol]}

Your example is actually equivalent to:

task :task_name => [:prerequisite_task, :another_task_we_depend_on] do
  ...

If you have no prerequisites you have to use the usual symbol notaion:

task :task_name do
  ...

The Ruby Style Guide suggests to prefer the newer, "JSON style", notation.

Answer 2

Syntax something: value means exactly same as :something => value . It is just a little more readable.