Method: Object#acts_like?

Defined in:
lib/active_support/core_ext/object/acts_like.rb

#acts_like?(duck) ⇒ Boolean

Provides a way to check whether some class acts like some other class based on the existence of an appropriately-named marker method.

A class that provides the same interface as SomeClass may define a marker method named acts_like_some_class? to signal its compatibility to callers of acts_like?(:some_class).

For example, Active Support extends Date to define an acts_like_date? method, and extends Time to define acts_like_time?. As a result, developers can call x.acts_like?(:time) and x.acts_like?(:date) to test duck-type compatibility, and classes that are able to act like Time can also define an acts_like_time? method to interoperate.

Note that the marker method is only expected to exist. It isn’t called, so its body or return value are irrelevant.

Example: A class that provides the same interface as String

This class may define:

class Stringish
  def acts_like_string?
  end
end

Then client code can query for duck-type-safeness this way:

Stringish.new.acts_like?(:string) # => true

Returns:

  • (Boolean) 


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# File 'lib/active_support/core_ext/object/acts_like.rb', line 33

def acts_like?(duck)
  case duck
  when :time
    respond_to? :acts_like_time?
  when :date
    respond_to? :acts_like_date?
  when :string
    respond_to? :acts_like_string?
  else
    respond_to? :"acts_like_#{duck}?"
  end
end