CODEWITHSUNDEEP
classlua
user514156
user514156

Reputation: 640

Higher order "methods" in lua

This code in lua will apply a function to a value

function Apply(f, value)
    return f(value)
end

I can then use it like this apply arbitrary functions calls on my game object like so

Apply(Draw, GameObject)
Apply(Update, GameObject)

Is it possible to instead do what I would, probably incorrectly, call a higher order method

function GameObject:Apply(f)
    return self:f()
end

What I eventually want to do is have a table of GameObjects, that I can call Methods on in batch. So using this "higher order method" concept that may not even exist I would create code that does the following.

...
--Create the batch object with three bullets in it
BatchGameObjects = BatchGameObject:new(Bullet1, Bullet2, Bullet3)


--Call equivelent to 
--Bullet1:DrawMethod() 
--Bullet2:DrawMethod()
--Bullet3:DrawMethod()

--Bullet1:UpdateMethod() 
--Bullet2:UpdateMethod()
--Bullet3:UpdateMethod()

BatchGameObjects:Apply(DrawMethod)
BatchGameObjects:Apply(UpdateMethod)

Upvotes: 2

Views: 109

Answers (2)

Oleg V. Volkov
Oleg V. Volkov

Reputation: 22481

You'll probably want to pass function NAME if you're dealing with methods on other objects, because methods with same name on different objects may resolve to very different functions.

function BatchGameObjects:Apply(function_name)
   -- ... or iterate on objects in any other way that matches how you store them ...
   for idx = 1, #self.object_list do
      local object = self.object_list[idx]
      object[function_name](object)
   end
end

Upvotes: 3

catwell
catwell

Reputation: 7020

function GameObject:Apply(f)
    return f(self)
end

Upvotes: 2

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