class StateMachine::Branch

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.

Attributes

event_requirement[R]

The requirement for verifying the event being matched

if_condition[R]

The condition that must be met on an object

known_states[R]

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

state_requirements[R]

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

unless_condition[R]

The condition that must not be met on an object

Public Instance Methods

draw(graph, event, valid_states) click to toggle source

Draws a representation of this branch on the given graph. This will draw an edge between every state this branch matches from to either the configured to state or, if none specified, then a loopback to the from state.

For example, if the following from states are configured:

  • idling

  • first_gear

  • backing_up

…and the to state is parked, then the following edges will be created:

  • idling -> parked

  • first_gear -> parked

  • backing_up -> parked

Each edge will be labeled with the name of the event that would cause the transition.

The collection of edges generated on the graph will be returned.

    # File lib/state_machine/branch.rb
145 def draw(graph, event, valid_states)
146   state_requirements.inject([]) do |edges, state_requirement|
147     # From states determined based on the known valid states
148     from_states = state_requirement[:from].filter(valid_states)
149     
150     # If a to state is not specified, then it's a loopback and each from
151     # state maps back to itself
152     if state_requirement[:to].values.empty?
153       loopback = true
154     else
155       to_state = state_requirement[:to].values.first
156       to_state = to_state ? to_state.to_s : 'nil'
157       loopback = false
158     end
159     
160     # Generate an edge between each from and to state
161     from_states.each do |from_state|
162       from_state = from_state ? from_state.to_s : 'nil'
163       edges << graph.add_edge(from_state, loopback ? from_state : to_state, :label => event.to_s)
164     end
165     
166     edges
167   end
168 end
match(object, query = {}) click to toggle source

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

branch.match(object, :on => :ignite)  # => {:to => ..., :from => ..., :on => ...}
branch.match(object, :on => :park)    # => nil
    # File lib/state_machine/branch.rb
118 def match(object, query = {})
119   assert_valid_keys(query, :from, :to, :on, :guard)
120   
121   if (match = match_query(query)) && matches_conditions?(object, query)
122     match
123   end
124 end
matches?(object, query = {}) click to toggle source

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 = StateMachine::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
   # File lib/state_machine/branch.rb
89 def matches?(object, query = {})
90   !match(object, query).nil?
91 end

Protected Instance Methods

build_matcher(options, whitelist_option, blacklist_option) click to toggle source

Builds a matcher strategy to use for the given options. If neither a whitelist nor a blacklist option is specified, then an AllMatcher is built.

    # File lib/state_machine/branch.rb
174 def build_matcher(options, whitelist_option, blacklist_option)
175   assert_exclusive_keys(options, whitelist_option, blacklist_option)
176   
177   if options.include?(whitelist_option)
178     WhitelistMatcher.new(options[whitelist_option])
179   elsif options.include?(blacklist_option)
180     BlacklistMatcher.new(options[blacklist_option])
181   else
182     AllMatcher.instance
183   end
184 end
match_event(query) click to toggle source

Verifies that the event requirement matches the given query

    # File lib/state_machine/branch.rb
198 def match_event(query)
199   matches_requirement?(query, :on, event_requirement)
200 end
match_query(query) click to toggle source

Verifies that all configured requirements (event and state) match the given query. If a match is found, then a hash containing the event/state requirements that passed will be returned; otherwise, nil.

    # File lib/state_machine/branch.rb
189 def match_query(query)
190   query ||= {}
191   
192   if match_event(query) && (state_requirement = match_states(query))
193     state_requirement.merge(:on => event_requirement)
194   end
195 end
match_states(query) click to toggle source

Verifies that the state requirements match the given query. If a matching requirement is found, then it is returned.

    # File lib/state_machine/branch.rb
204 def match_states(query)
205   state_requirements.detect do |state_requirement|
206     [:from, :to].all? {|option| matches_requirement?(query, option, state_requirement[option])}
207   end
208 end
matches_conditions?(object, query) click to toggle source

Verifies that the conditionals for this branch evaluate to true for the given object

    # File lib/state_machine/branch.rb
218 def matches_conditions?(object, query)
219   query[:guard] == false ||
220   Array(if_condition).all? {|condition| evaluate_method(object, condition)} &&
221   !Array(unless_condition).any? {|condition| evaluate_method(object, condition)}
222 end
matches_requirement?(query, option, requirement) click to toggle source

Verifies that an option in the given query matches the values required for that option

    # File lib/state_machine/branch.rb
212 def matches_requirement?(query, option, requirement)
213   !query.include?(option) || requirement.matches?(query[option], query)
214 end