Represents a type of module in which class-level methods are proxied to another class, injecting a custom :if condition along with method.
This is used for being able to automatically include conditionals which check the current state in class-level methods that have configuration options.
class Vehicle class << self attr_accessor :validations def validate(options, &block) validations << options end end self.validations = [] attr_accessor :state, :simulate def moving? self.class.validations.all? {|validation| validation[:if].call(self)} end end
In the above class, a simple set of validation behaviors have been defined. Each validation consists of a configuration like so:
Vehicle.validate :unless => :simulate Vehicle.validate :if => lambda {|vehicle| ...}
In order to scope conditions, a condition proxy can be created to the Vehicle class. For example,
proxy = StateMachine::ConditionProxy.new(Vehicle, lambda {|vehicle| vehicle.state == 'first_gear'}) proxy.validate(:unless => :simulate) vehicle = Vehicle.new # => #<Vehicle:0xb7ce491c @simulate=nil, @state=nil> vehicle.moving? # => false vehicle.state = 'first_gear' vehicle.moving? # => true vehicle.simulate = true vehicle.moving? # => false
Hooks in condition-merging to methods that don't exist in this module
# File lib/state_machine/condition_proxy.rb, line 60 def method_missing(*args, &block) # Get the configuration if args.last.is_a?(Hash) options = args.last else args << options = {} end # Get any existing condition that may need to be merged if_condition = options.delete(:if) unless_condition = options.delete(:unless) # Provide scope access to configuration in case the block is evaluated # within the object instance proxy = self proxy_condition = @condition # Replace the configuration condition with the one configured for this # proxy, merging together any existing conditions options[:if] = lambda do |*args| # Block may be executed within the context of the actual object, so # it'll either be the first argument or the executing context object = args.first || self proxy.evaluate_method(object, proxy_condition) && Array(if_condition).all? {|condition| proxy.evaluate_method(object, condition)} && !Array(unless_condition).any? {|condition| proxy.evaluate_method(object, condition)} end # Evaluate the method on the original class with the condition proxied # through @klass.send(*args, &block) end
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