class StateMachines::State

A state defines a value that an attribute can be in after being transitioned 0 or more times. States can represent a value of any type in Ruby, though the most common (and default) type is String.

In addition to defining the machine's value, a state can also define a behavioral context for an object when that object is in the state. See StateMachines::Machine#state for more information about how state-driven behavior can be utilized.

Attributes

cache[RW]

Whether this state's value should be cached after being evaluated

human_name[W]

The human-readable name for the state

initial[RW]

Whether or not this state is the initial state to use for new objects

initial?[RW]

Whether or not this state is the initial state to use for new objects

machine[RW]

The state machine for which this state is defined

matcher[RW]

A custom lambda block for determining whether a given value matches this state

name[R]

The unique identifier for the state used in event and callback definitions

qualified_name[R]

The fully-qualified identifier for the state, scoped by the machine's namespace

value[W]

The value that is written to a machine's attribute when an object transitions into this state

Public Instance Methods

call(object, method, *args, &block) click to toggle source

Calls a method defined in this state's context on the given object. All arguments and any block will be passed into the method defined.

If the method has never been defined for this state, then a NoMethodError will be raised.

# File lib/state_machines/state.rb, line 214
def call(object, method, *args, &block)
  options = args.last.is_a?(Hash) ? args.pop : {}
  options = {:method_name => method}.merge(options)
  state = machine.states.match!(object)

  if state == self && object.respond_to?(method)
    object.send(method, *args, &block)
  elsif method_missing = options[:method_missing]
    # Dispatch to the superclass since the object either isn't in this state
    # or this state doesn't handle the method
    begin
      method_missing.call
    rescue NoMethodError => ex
      if ex.name.to_s == options[:method_name].to_s && ex.args == args
        # No valid context for this method
        raise InvalidContext.new(object, "State #{state.name.inspect} for #{machine.name.inspect} is not a valid context for calling ##{options[:method_name]}")
      else
        raise
      end
    end
  end
end
context(&block) click to toggle source

Defines a context for the state which will be enabled on instances of the owner class when the machine is in this state.

This can be called multiple times. Each time a new context is created, a new module will be included in the owner class.

# File lib/state_machines/state.rb, line 176
    def context(&block)
      # Include the context
      context = @context
      machine.owner_class.class_eval { include context }

      # Evaluate the method definitions and track which ones were added
      old_methods = context_methods
      context.class_eval(&block)
      new_methods = context_methods.to_a.select { |(name, method)| old_methods[name] != method }

      # Alias new methods so that the only execute when the object is in this state
      new_methods.each do |(method_name, method)|
        context_name = context_name_for(method_name)
        context.class_eval "          alias_method :"#{context_name}", :#{method_name}
          def #{method_name}(*args, &block)
            state = self.class.state_machine(#{machine.name.inspect}).states.fetch(#{name.inspect})
            options = {:method_missing => lambda {super(*args, &block)}, :method_name => #{method_name.inspect}}
            state.call(self, :"#{context_name}", *(args + [options]), &block)
          end
", __FILE__, __LINE__ + 1
      end

      true
    end
context_methods() click to toggle source

The list of methods that have been defined in this state's context

# File lib/state_machines/state.rb, line 203
def context_methods
  @context.instance_methods.inject({}) do |methods, name|
    methods.merge(name.to_sym => @context.instance_method(name))
  end
end
description(options = {}) click to toggle source

Generates a human-readable description of this state's name / value:

For example,

State.new(machine, :parked).description                               # => "parked"
State.new(machine, :parked, :value => :parked).description            # => "parked"
State.new(machine, :parked, :value => nil).description                # => "parked (nil)"
State.new(machine, :parked, :value => 1).description                  # => "parked (1)"
State.new(machine, :parked, :value => lambda {Time.now}).description  # => "parked (*)

Configuration options:

  • :human_name - Whether to use this state's human name in the description or just the internal name

# File lib/state_machines/state.rb, line 122
def description(options = {})
  label = options[:human_name] ? human_name : name
  description = label ? label.to_s : label.inspect
  description << " (#{@value.is_a?(Proc) ? '*' : @value.inspect})" unless name.to_s == @value.to_s
  description
end
draw(graph, options = {}) click to toggle source
# File lib/state_machines/state.rb, line 237
def draw(graph, options = {})
  fail NotImplementedError
end
final?() click to toggle source

Determines whether there are any states that can be transitioned to from this state. If there are none, then this state is considered final. Any objects in a final state will remain so forever given the current machine's definition.

# File lib/state_machines/state.rb, line 93
def final?
  !machine.events.any? do |event|
    event.branches.any? do |branch|
      branch.state_requirements.any? do |requirement|
        requirement[:from].matches?(name) && !requirement[:to].matches?(name, :from => name)
      end
    end
  end
end
human_name(klass = @machine.owner_class) click to toggle source

Transforms the state name into a more human-readable format, such as “first gear” instead of “first_gear”

# File lib/state_machines/state.rb, line 105
def human_name(klass = @machine.owner_class)
  @human_name.is_a?(Proc) ? @human_name.call(self, klass) : @human_name
end
inspect() click to toggle source

Generates a nicely formatted description of this state's contents.

For example,

state = StateMachines::State.new(machine, :parked, :value => 1, :initial => true)
state   # => #<StateMachines::State name=:parked value=1 initial=true context=[]>
# File lib/state_machines/state.rb, line 247
def inspect
  attributes = [[:name, name], [:value, @value], [:initial, initial?]]
  "#<#{self.class} #{attributes.map { |attr, value| "#{attr}=#{value.inspect}" } * ' '}>"
end
matches?(other_value) click to toggle source

Determines whether this state matches the given value. If no matcher is configured, then this will check whether the values are equivalent. Otherwise, the matcher will determine the result.

For example,

# Without a matcher
state = State.new(machine, :parked, :value => 1)
state.matches?(1)           # => true
state.matches?(2)           # => false

# With a matcher
state = State.new(machine, :parked, :value => lambda {Time.now}, :if => lambda {|value| !value.nil?})
state.matches?(nil)         # => false
state.matches?(Time.now)    # => true
# File lib/state_machines/state.rb, line 167
def matches?(other_value)
  matcher ? matcher.call(other_value) : other_value == value
end
value(eval = true) click to toggle source

The value that represents this state. This will optionally evaluate the original block if it's a lambda block. Otherwise, the static value is returned.

For example,

State.new(machine, :parked, :value => 1).value                        # => 1
State.new(machine, :parked, :value => lambda {Time.now}).value        # => Tue Jan 01 00:00:00 UTC 2008
State.new(machine, :parked, :value => lambda {Time.now}).value(false) # => <Proc:0xb6ea7ca0@...>
# File lib/state_machines/state.rb, line 138
def value(eval = true)
  if @value.is_a?(Proc) && eval
    if cache_value?
      @value = @value.call
      machine.states.update(self)
      @value
    else
      @value.call
    end
  else
    @value
  end
end

Private Instance Methods

add_predicate() click to toggle source

Adds a predicate method to the owner class so long as a name has actually been configured for the state

# File lib/state_machines/state.rb, line 260
def add_predicate
  # Checks whether the current value matches this state
  machine.define_helper(:instance, "#{qualified_name}?") do |machine, object|
    machine.states.matches?(object, name)
  end
end
cache_value?() click to toggle source

Should the value be cached after it's evaluated for the first time?

# File lib/state_machines/state.rb, line 254
def cache_value?
  @cache
end
context_name_for(method) click to toggle source

Generates the name of the method containing the actual implementation

# File lib/state_machines/state.rb, line 268
def context_name_for(method)
  :"__#{machine.name}_#{name}_#{method}_#{@context.object_id}__"
end