module Aquarium::Extras::DesignByContract

A simple Design by Contract module. Adds advice to test that the contract, which is specified with a block passes. Note that it doesn't attempt to handle the correct behavior under contract inheritance. A usage example is included in the Examples as part of the distribution and it is also shown on the web site. Normally, you want to disable the contracts in production runs, so you avoid the overhead. To do this effectively, call DesignByContract.disable_all before any contracts are created. That will prevent all of the aspects from being created along with their overhead. Warning: This module automatically includes Aquarium::DSL into the class with the contract and it adds the :precondition, :postcondition, and the :invariant methods to Object!

Public Class Methods

disable_all() click to toggle source

Disable creation of any subsequent contracts and disable execution of existing contracts. That is, while contracts are disabled, it no existing contracts will be executed and any attempts to define new contracts will be ignored.

   # File lib/aquarium/extras/design_by_contract.rb
36 def self.disable_all
37   @@enabled = false
38 end

enable_all() click to toggle source

Enable creation and execution of contracts

   # File lib/aquarium/extras/design_by_contract.rb
29 def self.enable_all
30   @@enabled = true
31 end

Public Instance Methods

invariant(*args, &contract_block) click to toggle source

   # File lib/aquarium/extras/design_by_contract.rb
52 def invariant *args, &contract_block
53   return unless @@enabled
54   message = handle_message_arg args
55   Aspect.new make_args(:around, *args) do |jp, obj, *params|
56     DesignByContract.test_condition "invariant failure (before invocation): #{message}", jp, obj, *params, &contract_block
57     result = jp.proceed
58     DesignByContract.test_condition "invariant failure (after invocation): #{message}", jp, obj, *params, &contract_block
59     result
60   end
61 end

postcondition(*args, &contract_block) click to toggle source

   # File lib/aquarium/extras/design_by_contract.rb
46 def postcondition *args, &contract_block
47   return unless @@enabled
48   message = handle_message_arg args
49   add_advice :after_returning, "postcondition", message, *args, &contract_block
50 end

precondition(*args, &contract_block) click to toggle source

   # File lib/aquarium/extras/design_by_contract.rb
40 def precondition *args, &contract_block
41   return unless @@enabled
42   message = handle_message_arg args
43   add_advice :before, "precondition", message, *args, &contract_block
44 end