Module: Insist::Predicates

Includes:
Assert
Included in:
Insist
Defined in:
lib/insist/predicates.rb

Constant Summary collapse

PREDICATE_METHOD_RE = 
/\?$/

Instance Method Summary collapse

Methods included from Assert

#assert

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(m, *args) ⇒ Object

Pass through any ‘foo?’ style method calls to the ‘value’ and fail if the the return is false.



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# File 'lib/insist/predicates.rb', line 25

def method_missing(m, *args)
  # If this is a predicate method (ends in question mark)
  # call it on the value and assert truthiness.
  if PREDICATE_METHOD_RE.match(m.to_s)
    insist { value }.respond_to?(m)

    # call the method, like .empty?, result must be truthy.
    result = value.send(m, *args)
    assert(result, 
           "#{value.class}{#{value.inspect}}##{m}(#{args.join(",")}) " \
           "expected to return a truthy value, but returned #{result}")
    return result
  else
    return super(m, *args)
  end
end

Instance Method Details

#is_a?(klass) ⇒ Boolean

Fails if the value.is_a?(klass) returns false.

insist { “hurray” }.is_a?(Number)

Returns:

  • (Boolean) 


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# File 'lib/insist/predicates.rb', line 19

def is_a?(klass)
  assert(value.is_a?(klass), "#{value.class} is not a #{klass}")
end

#respond_to?(method) ⇒ Boolean

Fails if the value does not respond to a method.

insist { “hurray” }.respond_to?(:size)

Returns:

  • (Boolean) 


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# File 'lib/insist/predicates.rb', line 11

def respond_to?(method)
  assert(value.respond_to?(method),
         "#{value.class} does not respond to the '#{method}' method")
end