class EnumStateMachine::Callback
Callbacks represent hooks into objects that allow logic to be triggered before, after, or around a specific set of transitions.
Attributes
Determines whether to automatically bind the callback to the object being transitioned. This only applies to callbacks that are defined as lambda blocks (or Procs). Some integrations handle callbacks by executing them bound to the object involved, while other integrations, such as ActiveRecord, pass the object as an argument to the callback. This can be configured on an application-wide basis by setting this configuration to true
or false
. The default value is false
.
Examples¶ ↑
When not bound to the object:
class Vehicle state_machine do before_transition do |vehicle| vehicle.set_alarm end end def set_alarm ... end end
When bound to the object:
EnumStateMachine::Callback.bind_to_object = true class Vehicle state_machine do before_transition do self.set_alarm end end def set_alarm ... end end
The application-wide terminator to use for callbacks when not explicitly defined. Terminators determine whether to cancel a callback chain based on the return value of the callback.
See EnumStateMachine::Callback#terminator
for more information.
The branch that determines whether or not this callback can be invoked based on the context of the transition. The event, from state, and to state must all match in order for the branch to pass.
See EnumStateMachine::Branch
for more information.
An optional block for determining whether to cancel the callback chain based on the return value of the callback. By default, the callback chain never cancels based on the return value (i.e. there is no implicit terminator). Certain integrations, such as ActiveRecord, change this default value.
Examples¶ ↑
Canceling the callback chain without a terminator:
class Vehicle state_machine do before_transition do |vehicle| throw :halt end end end
Canceling the callback chain with a terminator value of false
:
class Vehicle state_machine do before_transition do |vehicle| false end end end
The type of callback chain this callback is for. This can be one of the following:
-
before
-
after
-
around
-
failure
Public Class Methods
Creates a new callback that can get called based on the configured options.
In addition to the possible configuration options for branches, the following options can be configured:
-
:bind_to_object
- Whether to bind the callback to the object involved. If set to false, the object will be passed as a parameter instead. Default is integration-specific or set to the application default. -
:terminator
- A block/proc that determines what callback results should cause the callback chain to halt (if not using the defaultthrow :halt
technique).
More information about how those options affect the behavior of the callback can be found in their attribute definitions.
# File lib/enum_state_machine/callback.rb 119 def initialize(type, *args, &block) 120 @type = type 121 raise ArgumentError, 'Type must be :before, :after, :around, or :failure' unless [:before, :after, :around, :failure].include?(type) 122 123 options = args.last.is_a?(Hash) ? args.pop : {} 124 @methods = args 125 @methods.concat(Array(options.delete(:do))) 126 @methods << block if block_given? 127 raise ArgumentError, 'Method(s) for callback must be specified' unless @methods.any? 128 129 options = {:bind_to_object => self.class.bind_to_object, :terminator => self.class.terminator}.merge(options) 130 131 # Proxy lambda blocks so that they're bound to the object 132 bind_to_object = options.delete(:bind_to_object) 133 @methods.map! do |method| 134 bind_to_object && method.is_a?(Proc) ? bound_method(method) : method 135 end 136 137 @terminator = options.delete(:terminator) 138 @branch = Branch.new(options) 139 end
Public Instance Methods
Runs the callback as long as the transition context matches the branch requirements configured for this callback. If a block is provided, it will be called when the last method has run.
If a terminator has been configured and it matches the result from the evaluated method, then the callback chain should be halted.
# File lib/enum_state_machine/callback.rb 153 def call(object, context = {}, *args, &block) 154 if @branch.matches?(object, context) 155 run_methods(object, context, 0, *args, &block) 156 true 157 else 158 false 159 end 160 end
Gets a list of the states known to this callback by looking at the branch's known states
# File lib/enum_state_machine/callback.rb 143 def known_states 144 branch.known_states 145 end
Private Instance Methods
Generates a method that can be bound to the object being transitioned when the callback is invoked
# File lib/enum_state_machine/callback.rb 195 def bound_method(block) 196 type = self.type 197 arity = block.arity 198 arity += 1 if arity >= 0 # Make sure the object gets passed 199 arity += 1 if arity == 1 && type == :around # Make sure the block gets passed 200 201 method = if RUBY_VERSION >= '1.9' 202 lambda do |object, *args| 203 object.instance_exec(*args, &block) 204 end 205 else 206 # Generate a thread-safe unbound method that can be used on any object. 207 # This is a workaround for not having Ruby 1.9's instance_exec 208 unbound_method = Object.class_eval do 209 time = Time.now 210 method_name = "__bind_#{time.to_i}_#{time.usec}" 211 define_method(method_name, &block) 212 method = instance_method(method_name) 213 remove_method(method_name) 214 method 215 end 216 217 # Proxy calls to the method so that the method can be bound *and* 218 # the arguments are adjusted 219 lambda do |object, *args| 220 unbound_method.bind(object).call(*args) 221 end 222 end 223 224 # Proxy arity to the original block 225 (class << method; self; end).class_eval do 226 define_method(:arity) { arity } 227 end 228 229 method 230 end
Runs all of the methods configured for this callback.
When running around
callbacks, this will evaluate each method and yield when the last method has yielded. The callback will only halt if one of the methods does not yield.
For all other types of callbacks, this will evaluate each method in order. The callback will only halt if the resulting value from the method passes the terminator.
# File lib/enum_state_machine/callback.rb 172 def run_methods(object, context = {}, index = 0, *args, &block) 173 if type == :around 174 if current_method = @methods[index] 175 yielded = false 176 evaluate_method(object, current_method, *args) do 177 yielded = true 178 run_methods(object, context, index + 1, *args, &block) 179 end 180 181 throw :halt unless yielded 182 else 183 yield if block_given? 184 end 185 else 186 @methods.each do |method| 187 result = evaluate_method(object, method, *args) 188 throw :halt if @terminator && @terminator.call(result) 189 end 190 end 191 end