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.
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
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
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
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
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
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
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
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
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