Class Declaration Statements

In the body of a class declaration, we can have normal expressions in addition to key/value pairs. In this context, self is equal to the class object.

Here is an alternative way to create a class variable compared to what’s described above:

MoonScript:

class Things
  @class_var = "hello world"

Lua:

local Things
do
  local _base_0 = { }
  _base_0.__index = _base_0
  local _class_0 = setmetatable({
    __init = function() end,
    __base = _base_0,
    __name = "Things"
  }, {
    __index = _base_0,
    __call = function(cls, ...)
      local _self_0 = setmetatable({}, _base_0)
      cls.__init(_self_0, ...)
      return _self_0
    end
  })
  _base_0.__class = _class_0
  local self = _class_0
  self.class_var = "hello world"
  Things = _class_0
end

These expressions are executed after all the properties have been added to the base.

All variables declared in the body of the class are local to the classes properties. This is convenient for placing private values or helper functions that only the class methods can access:

MoonScript:

class MoreThings
  secret = 123
  log = (msg) -> print "LOG:", msg

  some_method: =>
    log "hello world: " .. secret