README.md

Rude.rb

Rude.rb is a Ruby implementation of the rule-based dispatcher control-flow pattern Rude.

Usage

Creating an instance

require_relative "rude.rb"
rude = Rude.new()

Adding a rule

inst = SomeClass.new()
rude.add_rule(inst.method(:methodname1), inst.method(:methodname2), inst.method(:methodname3))

add_rule accepts three arguments: the condition to check, the function to call when the result is true, and the function to call when it is false. Each argument is a function reference or nil.

The return value of conditions must be true for proceeding with the yes callback and false with the no branch. When a condition returns nil, Rude exits the condition chain. In this case, the yes and no callbacks are not necessary. These conditions are usually exit points.

Checking conditions

Checking conditions based on the applied rules is triggered by calling rude.check().

rude.check(inst.method(:methodname1))

This specifies the entry point in the condition chain and can be set to any valid rule condition.

Example

The example provided is a subprocess launcher. It shows how to encapsulate the control flow logic for determining how to launch a subprocess in Ruby. It is based on the flow chart at https://stackoverflow.com/a/30463900

Benefits

• Rude allows for an on-demand execution of a chain of dynamic if-then-else statements - hereinafter referred to as rules.
• The control flow is easy to manage and the logic can be modified by simply changing the callbacks in the rules.
• The chain of condition checking can be exited or paused at any given point.
• The position in the rule hierarchy can be stored and the execution resumed at a later stage by setting the entry point.
• Each rule is seen as a separate and independent logical unit.
• Individual rules and groups of rules can be easily moved around.
• Rules can be generated dynamically or loaded from a datasource.
• The dispatcher makes it possible to ditch the rigid static conditional model in favour of a considerably more flexible one.