Memoization

---

Rectangle

require 'Coat'

class 'Rectangle'
has.x               = { is = 'rw', isa = 'number', required = true }
has.y               = { is = 'rw', isa = 'number', required = true }

function overload:__tostring ()
    return self._CLASS .. ':' .. self.x .. 'x' .. self.y
end

function method:_get_area ()
    return self.x * self.y
end

function method:getWeight (density)
    return self.x * self.y * density
end
memoize 'getWeight'

A method could become memoized after its definition.

The memoization is not reversable.

require 'Rectangle'

Rectangle.memoize '_get_area'

All values are memoized in an uniq table Coat.Meta.Class._CACHE. This table uses weak reference.

The key is composed of the name of the method and the concatenation of stringified parameter (self is the first one). It is important to define the appropriate __tostring for each not basic type.

Special case : ImmutableRectangle

Computed attribute of immutable object could be implemented with lazy_build.

require 'Coat'

class 'ImmutableRectangle'
extends 'Rectangle'
has.x               = { '+', is = 'ro' }
has.y               = { '+', is = 'ro' }
has.area            = { is = 'ro', lazy_build = true }

function method:_build_area ()
    return self.x * self.y
end