Classes

The Lua language has by default no class construct. But the Renoises lua API has a simple OO support inbuilt -> class "MyClass". All Renoise API objects use such classes and you can use them too in your tools.

See luabind docs for more technical info and below for some simple examples

Examples

-- abstract class

class 'Animal'
  function Animal:__init(name)
    self.name = name
    self.can_fly = nil
  end  

  function Animal:__tostring()
    assert(self.can_fly ~= nil, "I don't know if I can fly or not")
    
    return ("I am a %s (%s) and I %s fly"):format(self.name, type(self), 
      (self.can_fly and "can fly" or "can not fly"))
  end


-- derived classes

-- MAMMAL
class 'Mammal' (Animal)
  function Mammal:__init(str)
    Animal.__init(self, str)
    self.can_fly = false
  end

-- BIRD
class 'Bird' (Animal)
  function Bird:__init(str)
    Animal.__init(self, str)
    self.can_fly = true
  end

-- FISH
class 'Fish' (Animal)
  function Fish:__init(str)
    Animal.__init(self, str)
    self.can_fly = false
  end


-- run

local farm = table.create()

farm:insert(Mammal("cow"))
farm:insert(Bird("sparrow"))
farm:insert(Fish("bass"))

print(("type(Mammal('cow')) -> %s"):format(type(Mammal("cow"))))
print(("type(Mammal) -> %s"):format(type(Mammal)))

for _,animal in pairs(farm) do
  print(animal)
end

Something to keep in mind:

• constructor function MyClass:__init(args) must be defined for each class, or the class can't be used to instantiate objects.

• class defs are always global, so even locally defined classes will be registered globally.

Class operators

You can overload most operators in Lua for your classes. You do this by simply declaring a member function with the same name as an operator (the name of the metamethods in Lua).

The operators you can overload are:

• __add
• __sub
• __mul
• __div
• __pow
• __lt
• __le
• __eq
• __call
• __unm
• __tostring
• __len

Note: __tostring isn't really an operator, but it's the metamethod that is called by the standard library's tostring() function.