andypike/rectify

Boolean Parameter is a special case of Control Couple, where a method parameter is defaulted to true or false. A Boolean Parameter effectively permits a method's caller to decide which execution path to take. This is a case of bad cohesion. You're creating a dependency between methods that is not really necessary, thus increasing coupling.

Example

Given

class Dummy
  def hit_the_switch(switch = true)
    if switch
      puts 'Hitting the switch'
      # do other things...
    else
      puts 'Not hitting the switch'
      # do other things...
    end
  end
end

Reek would emit the following warning:

test.rb -- 3 warnings:
  [1]:Dummy#hit_the_switch has boolean parameter 'switch' (BooleanParameter)
  [2]:Dummy#hit_the_switch is controlled by argument switch (ControlParameter)

Note that both smells are reported, Boolean Parameter and Control Parameter.

Getting rid of the smell

This is highly dependent on your exact architecture, but looking at the example above what you could do is:

• Move everything in the if branch into a separate method
• Move everything in the else branch into a separate method
• Get rid of the hit_the_switch method alltogether
• Make the decision what method to call in the initial caller of hit_the_switch

Reek reports a Manual Dispatch smell if it finds source code that manually checks whether an object responds to a method before that method is called. Manual dispatch is a type of Simulated Polymorphism which leads to code that is harder to reason about, debug, and refactor.

Example

class MyManualDispatcher
  attr_reader :foo

  def initialize(foo)
    @foo = foo
  end

  def call
    foo.bar if foo.respond_to?(:bar)
  end
end

Reek would emit the following warning:

test.rb -- 1 warning:
  [9]: MyManualDispatcher manually dispatches method call (ManualDispatch)

Reek reports a Manual Dispatch smell if it finds source code that manually checks whether an object responds to a method before that method is called. Manual dispatch is a type of Simulated Polymorphism which leads to code that is harder to reason about, debug, and refactor.

Example

class MyManualDispatcher
  attr_reader :foo

  def initialize(foo)
    @foo = foo
  end

  def call
    foo.bar if foo.respond_to?(:bar)
  end
end

Reek would emit the following warning:

test.rb -- 1 warning:
  [9]: MyManualDispatcher manually dispatches method call (ManualDispatch)

Classes and modules are the units of reuse and release. It is therefore considered good practice to annotate every class and module with a brief comment outlining its responsibilities.

Example

Given

class Dummy
  # Do things...
end

Reek would emit the following warning:

test.rb -- 1 warning:
  [1]:Dummy has no descriptive comment (IrresponsibleModule)

Fixing this is simple - just an explaining comment:

# The Dummy class is responsible for ...
class Dummy
  # Do things...
end