state_machine

StateMachine::Machine#define_helper

Defines a new helper method in an instance or class scope with the given
name.  If the method is already defined in the scope, then this will not
override it.

If passing in a block, there are two side effects to be aware of
1. The method cannot be chained, meaning that the block cannot call +super+
2. If the method is already defined in an ancestor, then it will not get
   overridden and a warning will be output.

Example:

  # Instance helper
  machine.define_helper(:instance, :state_name) do |machine, object|
    machine.states.match(object).name
  end
  
  # Class helper
  machine.define_helper(:class, :state_machine_name) do |machine, klass|
    "State"
  end

You can also define helpers using string evaluation like so:

  # Instance helper
  machine.define_helper :instance, <<-end_eval, __FILE__, __LINE__ + 1
    def state_name
      self.class.state_machine(:state).states.match(self).name
    end
  end_eval
  
  # Class helper
  machine.define_helper :class, <<-end_eval, __FILE__, __LINE__ + 1
    def state_machine_name
      "State"
    end
  end_eval

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