I had been wondering how that kind of Ruby magic works for some time.
MyClass.new.configure do
name "the best class"
purpose "to kick ass"
tags "ruby", "configuration", "dsl"
end
You have to be willing to use the nasty sounding instance_eval method. It’s
scary but trivial:
def MyClass
def configure &block
# The block will be called with the
# MyClass instance as self.
instance_eval &block
end
def name value
@name = value
end
def purpose value
@purpose = value
end
def tags *args
@tags = args
end
end
Note that you can also make your own DSL configuration file (like unicorn) using the same technique:
# File: /my/project/config.rb
name "my configuration"
purpose "to look prettier than YAML"
tags "ruby", "configuration", "dsl"
Add this method to the above class to load it:
class MyClass
def configure_from_file config_file
instance_eval File.read(config_file), config_file
end
end
See Ruby DSLs: instance_eval with delegation for a more complete
take on this. Take look at Ruby’s BasicObject class for
the original documentation.