Ruby How to inherit from object given in constructor

Question

I'm new in dynamic typed programming languages, and I have problem with inheritance. In my case I had followed Ruby class:

class Vertex
  def initialize(given_object, *edges)
    @o = given_object
    @e = edges
  end
end

And I need to extend Vertex class for object class,

class Vertex < given_object

So I need to extends my object from object that is given in constructor

I know that is basic knowledge but as I mentioned earlier I'm totally new in dynamic typed languages.

@edited: Ok I understand, so lets consider this example:

class TestClass
  def initialize(object)
    @object = object
    TestClass < object.class
  end
end

#now In code I want to run each method on TestClass because it should inherit from Array
v = TestClass.new([1,2,3,4,5,6,7,8,9])    
v.each { |number| print number}

but I got interpreter error

 `<top (required)>': undefined method `each' for #<TestClass:0x00000001275960 @object=[1, 2, 3, 4, 5, 6, 7, 8, 9]> (NoMethodError)

Mazeryt, re your edit. You have not defined the method `each` for `TestClass` and `each` is not defined for any of its ancestors: `TestClass.ancestors => [TestClass, Object, PP::ObjectMixin, Kernel, BasicObject]`. Hence, the undefined error exception. You define `TestClass` with the `class` keyword. `TestClass < object.class` is here `TestClass < Array`, which tells you whether `TestClass` is a subclass of `Array`; it does not change the parentage of `TestClass`. Here it returns `nil`. See [Module#<](http://ruby-doc.org/core-2.1.0/Module.html#method-i-3C). — Cary Swoveland, Feb 12 '14 at 22:06

score 1 · Answer 1 · edited May 23 '17 at 11:50

1

Unfortunately, you can't alter an object's superclass at runtime.

See How to dynamically alter inheritance in Ruby for some alternate ideas that may work for you.

edited May 23 '17 at 11:50

Community

1
1

answered Feb 12 '14 at 19:44

score 1 · Accepted Answer · answered Feb 13 '14 at 12:53

You probably wish to use Decorator pattern, when all methods are proxied to given model:

class TestClass
  def initialize(object)
    @object = object
  end

  def method_missing(method, *args, &block)
    @object.send(method, *args, &block)
  end
end

v = TestClass.new([1,2,3,4,5,6,7,8,9])    
v.each { |number| print number}

Andrew Backes · Answer 3 · 2014-02-13T13:32:20.890

0

The def keyword is used for methods, not classes. Try using class vertex and see if your issue is resolved.

edited Feb 13 '14 at 13:32

answered Feb 12 '14 at 19:28

Andrew Backes

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Thanks I edited my question, can You look on edited? – Mazeryt Feb 12 '14 at 19:41
The `def` keyword is used for methods, not functions. – Jörg W Mittag Feb 13 '14 at 01:55
@JörgWMittag Woops, you are right. Been doing too much functional programming lately :) – Andrew Backes Feb 13 '14 at 13:33

Ruby How to inherit from object given in constructor

3 Answers3