Ruby Hooks

The hook execute option can also be provided Ruby code instead of a string. Here’s how it works:

  1. When the execute option is a String: Terraspace will shell out and run it as a script.
  2. When the execute option is a Ruby object: Terraspace will perform the call method on the object or class.

Ruby Class

When the Ruby object is a class with an instance method call, Terraspace creates a new instance of the class and runs its call method. Example:

config/hooks/terraspace.rb

class EnvExporter
  def call
    ENV['SECRET_FOO'] = "bar"
  end
end

before("build",
  execute: EnvExporter,
)

Terraspace will do something like this:

EnvExporter.new.call

The example sets the SECRET_FOO environment variable. It is then available from ERB in the project files.

Ruby Object

When the Ruby object, Terraspace expects it to have a call method and will run it. Example:

config/hooks/terraspace.rb

before("compile",
  execute: lambda { ENV['SECRET_FOO'] = "hi2" }
)

Terraspace will do something like this:

@hook[:execute].call

Process Context

The context in which the hook runs is worth highlighting. When the execute option is a String, Terraspace runs the script in a new child process. This the script is an independent process, and whatever is done to its environment is segregated.

When the execute option a Ruby object, then Terraspace runs the hook within the same process. It means the hook can affect the same environment. IE: Setting environment variables.