Ruby Language Message Passing Interrupting Messages
Example
There are two ways to interrupt messages.
- Use
method_missingto interrupt any non defined message. - Define a method in middle of a chain to intercept the message
After interrupting messages, it is possible to:
- Reply to them.
- Send them somewhere else.
- Modify the message or its result.
Interrupting via method_missing and replying to message:
class Example
def foo
@foo
end
def method_missing name, data
return super unless name.to_s =~ /=$/
name = name.to_s.sub(/=$/, "")
instance_variable_set "@#{name}", data
end
end
e = Example.new
e.foo = :foo
e.foo # => :foo
Intercepting message and modifying it:
class Example
def initialize title, body
end
end
class SubExample < Example
end
Now let's imagine our data is "title:body" and we have to split them before calling Example. We can define initialize on SubExample.
class SubExample < Example
def initialize raw_data
processed_data = raw_data.split ":"
super processed_data[0], processed_data[1]
end
end
Intercepting message and sending it to another object:
class ObscureLogicProcessor
def process data
:ok
end
end
class NormalLogicProcessor
def process data
:not_ok
end
end
class WrapperProcessor < NormalLogicProcessor
def process data
return ObscureLogicProcessor.new.process data if data.obscure?
super
end
end
