Class: StateMachines::Branch

Inherits:
Object
  • Object
show all
Includes:
EvalHelpers
Defined in:
lib/state_machines/branch.rb

Overview

Represents a set of requirements that must be met in order for a transition or callback to occur. Branches verify that the event, from state, and to state of the transition match, in addition to if/unless conditionals for an object's state.

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from EvalHelpers

#evaluate_method

Constructor Details

#initialize(options = {}) ⇒ Branch

Creates a new branch


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# File 'lib/state_machines/branch.rb', line 30

def initialize(options = {}) #:nodoc:
  # Build conditionals
  @if_condition = options.delete(:if)
  @unless_condition = options.delete(:unless)
  
  # Build event requirement
  @event_requirement = build_matcher(options, :on, :except_on)
  
  if (options.keys - [:from, :to, :on, :except_from, :except_to, :except_on]).empty?
    # Explicit from/to requirements specified
    @state_requirements = [{:from => build_matcher(options, :from, :except_from), :to => build_matcher(options, :to, :except_to)}]
  else
    # Separate out the event requirement
    options.delete(:on)
    options.delete(:except_on)
    
    # Implicit from/to requirements specified
    @state_requirements = options.collect do |from, to|
      from = WhitelistMatcher.new(from) unless from.is_a?(Matcher)
      to = WhitelistMatcher.new(to) unless to.is_a?(Matcher)
      {:from => from, :to => to}
    end
  end
  
  # Track known states.  The order that requirements are iterated is based
  # on the priority in which tracked states should be added.
  @known_states = []
  @state_requirements.each do |state_requirement|
    [:from, :to].each {|option| @known_states |= state_requirement[option].values}
  end
end

Instance Attribute Details

#event_requirementObject (readonly)

The requirement for verifying the event being matched


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# File 'lib/state_machines/branch.rb', line 17

def event_requirement
  @event_requirement
end

#if_conditionObject (readonly)

The condition that must be met on an object


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# File 'lib/state_machines/branch.rb', line 11

def if_condition
  @if_condition
end

#known_statesObject (readonly)

A list of all of the states known to this branch. This will pull states from the following options (in the same order):

  • from / except_from

  • to / except_to


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# File 'lib/state_machines/branch.rb', line 27

def known_states
  @known_states
end

#state_requirementsObject (readonly)

One or more requirements for verifying the states being matched. All requirements contain a mapping of => matcher, :to => matcher.


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# File 'lib/state_machines/branch.rb', line 21

def state_requirements
  @state_requirements
end

#unless_conditionObject (readonly)

The condition that must not be met on an object


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# File 'lib/state_machines/branch.rb', line 14

def unless_condition
  @unless_condition
end

Instance Method Details

#draw(graph, event, valid_states) ⇒ Object


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# File 'lib/state_machines/branch.rb', line 122

def draw(graph, event, valid_states)
 fail NotImplementedError
end

#match(object, query = {}) ⇒ Object

Attempts to match the given object / query against the set of requirements configured for this branch. In addition to matching the event, from state, and to state, this will also check whether the configured :if/:unless conditions pass on the given object.

If a match is found, then the event/state requirements that the query passed successfully will be returned. Otherwise, nil is returned if there was no match.

Query options:

  • :from - One or more states being transitioned from. If none are specified, then this will always match.

  • :to - One or more states being transitioned to. If none are specified, then this will always match.

  • :on - One or more events that fired the transition. If none are specified, then this will always match.

  • :guard - Whether to guard matches with the if/unless conditionals defined for this branch. Default is true.

Examples

branch = StateMachines::Branch.new(:parked => :idling, :on => :ignite)

branch.match(object, :on => :ignite)  # => {:to => ..., :from => ..., :on => ...}
branch.match(object, :on => :park)    # => nil

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# File 'lib/state_machines/branch.rb', line 114

def match(object, query = {})
  query.assert_valid_keys(:from, :to, :on, :guard)
  
  if (match = match_query(query)) && matches_conditions?(object, query)
    match
  end
end

#matches?(object, query = {}) ⇒ Boolean

Determines whether the given object / query matches the requirements configured for this branch. In addition to matching the event, from state, and to state, this will also check whether the configured :if/:unless conditions pass on the given object.

Examples

branch = StateMachines::Branch.new(:parked => :idling, :on => :ignite)

# Successful
branch.matches?(object, :on => :ignite)                                   # => true
branch.matches?(object, :from => nil)                                     # => true
branch.matches?(object, :from => :parked)                                 # => true
branch.matches?(object, :to => :idling)                                   # => true
branch.matches?(object, :from => :parked, :to => :idling)                 # => true
branch.matches?(object, :on => :ignite, :from => :parked, :to => :idling) # => true

# Unsuccessful
branch.matches?(object, :on => :park)                                     # => false
branch.matches?(object, :from => :idling)                                 # => false
branch.matches?(object, :to => :first_gear)                               # => false
branch.matches?(object, :from => :parked, :to => :first_gear)             # => false
branch.matches?(object, :on => :park, :from => :parked, :to => :idling)   # => false

Returns:

  • (Boolean)

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# File 'lib/state_machines/branch.rb', line 85

def matches?(object, query = {})
  !match(object, query).nil?
end