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
The requirement for verifying the event being matched
The condition that must be met on an object
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
One or more requirements for verifying the states being matched. All requirements contain a mapping of {:from => matcher, :to => matcher}.
The condition that must not be met on an object
Public Instance Methods
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.
# File lib/state_machine/branch.rb, line 143 def draw(graph, event, valid_states) state_requirements.each do |state_requirement| # From states determined based on the known valid states from_states = state_requirement[:from].filter(valid_states) # If a to state is not specified, then it's a loopback and each from # state maps back to itself if state_requirement[:to].values.empty? loopback = true else to_state = state_requirement[:to].values.first to_state = to_state ? to_state.to_s : 'nil' loopback = false end # Generate an edge between each from and to state from_states.each do |from_state| from_state = from_state ? from_state.to_s : 'nil' graph.add_edges(from_state, loopback ? from_state : to_state, :label => event.to_s) end end true end
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, line 118 def match(object, query = {}) assert_valid_keys(query, :from, :to, :on, :guard) if (match = match_query(query)) && matches_conditions?(object, query) match end end
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, line 89 def matches?(object, query = {}) !match(object, query).nil? end
Protected Instance Methods
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, line 172 def build_matcher(options, whitelist_option, blacklist_option) assert_exclusive_keys(options, whitelist_option, blacklist_option) if options.include?(whitelist_option) value = options[whitelist_option] value.is_a?(Matcher) ? value : WhitelistMatcher.new(options[whitelist_option]) elsif options.include?(blacklist_option) value = options[blacklist_option] raise ArgumentError, ":#{blacklist_option} option cannot use matchers; use :#{whitelist_option} instead" if value.is_a?(Matcher) BlacklistMatcher.new(value) else AllMatcher.instance end end
Verifies that the event requirement matches the given query
# File lib/state_machine/branch.rb, line 199 def match_event(query) matches_requirement?(query, :on, event_requirement) end
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, line 190 def match_query(query) query ||= {} if match_event(query) && (state_requirement = match_states(query)) state_requirement.merge(:on => event_requirement) end end
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, line 205 def match_states(query) state_requirements.detect do |state_requirement| [:from, :to].all? {|option| matches_requirement?(query, option, state_requirement[option])} end end
Verifies that the conditionals for this branch evaluate to true for the given object
# File lib/state_machine/branch.rb, line 219 def matches_conditions?(object, query) query[:guard] == false || Array(if_condition).all? {|condition| evaluate_method(object, condition)} && !Array(unless_condition).any? {|condition| evaluate_method(object, condition)} end
Verifies that an option in the given query matches the values required for that option
# File lib/state_machine/branch.rb, line 213 def matches_requirement?(query, option, requirement) !query.include?(option) || requirement.matches?(query[option], query) end