Provides a set of helper methods for evaluating methods within the context of an object.
Evaluates one of several different types of methods within the context of the given object. Methods can be one of the following types:
Symbol
Method / Proc
String
Below are examples of the various ways that a method can be evaluated on an object:
class Person def initialize(name) @name = name end def name @name end end class PersonCallback def self.run(person) person.name end end person = Person.new('John Smith') evaluate_method(person, :name) # => "John Smith" evaluate_method(person, PersonCallback.method(:run)) # => "John Smith" evaluate_method(person, Proc.new {|person| person.name}) # => "John Smith" evaluate_method(person, lambda {|person| person.name}) # => "John Smith" evaluate_method(person, '@name') # => "John Smith"
Additional arguments can be passed to the methods being evaluated. If the method defines additional arguments other than the object context, then all arguments are required.
For example,
person = Person.new('John Smith') evaluate_method(person, lambda {|person| person.name}, 21) # => "John Smith" evaluate_method(person, lambda {|person, age| "#{person.name} is #{age}"}, 21) # => "John Smith is 21" evaluate_method(person, lambda {|person, age| "#{person.name} is #{age}"}, 21, 'male') # => ArgumentError: wrong number of arguments (3 for 2)
# File lib/state_machine/eval_helpers.rb, line 53 def evaluate_method(object, method, *args, &block) case method when Symbol object.method(method).arity == 0 ? object.send(method, &block) : object.send(method, *args, &block) when Proc, Method args.unshift(object) arity = method.arity # Procs don't support blocks in < Ruby 1.9, so it's tacked on as an # argument for consistency across versions of Ruby if block_given? && Proc === method && arity != 0 if [1, 2].include?(arity) # Force the block to be either the only argument or the 2nd one # after the object (may mean additional arguments get discarded) args = args[0, arity - 1] + [block] else # Tack the block to the end of the args args << block end else # These method types are only called with 0, 1, or n arguments args = args[0, arity] if [0, 1].include?(arity) end method.call(*args, &block) when String eval(method, object.instance_eval {binding}, &block) else raise ArgumentError, 'Methods must be a symbol denoting the method to call, a block to be invoked, or a string to be evaluated' end end