bzr branch
/bzr/ld26
1
by Josh C
zoetrope 1.4 |
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-- Class: Class
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-- This is a simple OOP single-inheritance implementation based
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-- on the one suggested by <Programming in Lua at http://www.lua.org/pil/16.html>.
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-- One big difference from what you may be expecting is that there are no
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-- constructors per se; all subclasses share the same constructor method,
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-- which takes a table of properties that are mixed into the instance.
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-- e.g. Code like this:
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--
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-- (begin code)
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-- MyClass = Class:extend{ color = 'red', name = 'robin' }
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-- myObject = MyClass:new{ color = 'blue' }
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-- (end code)
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--
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-- Would set myObject to have a color of 'blue' and a name of 'robin'. There is a
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-- <onNew> event handler you can use to perform initialization based on these values.
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--
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-- Event: onNew
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-- Called once, when a new object is created via <new()>.
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Class = |
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{
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-- Method: extend
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-- Creates a subclass of a class object, replacing any class properties
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-- with those in the object passed. It also sets the subclass's prototype
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-- property to this class. This alters the passed table in-place.
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--
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-- Arguments:
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-- obj - table of properties
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--
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-- Returns:
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-- subclassed table
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extend = function (self, obj) |
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obj = obj or {} |
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assert(type(obj) == 'table', 'must extend a table, received a ' .. type(obj)) |
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-- copy any table properties into the subclass, so that
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-- it does not accidentally overwrite them
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for key, value in pairs(self) do |
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if key ~= '__index' and not obj[key] and type(value) == 'table' then |
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obj[key] = copyTable(self[key]) |
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end
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end
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-- __index work to set up inheritance and getters/setters
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obj = obj or {} |
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setmetatable(obj, self) |
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self.__index = self |
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obj.prototype = self |
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return obj |
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end, |
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-- Method: new
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-- Extends an object and calls its onNew() handler if it is defined.
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-- This handler is meant for object-specific initialization,
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-- not class-wide work.
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--
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-- Arguments:
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-- obj - table of properties that the new object starts with,
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-- overriding anything set in the class
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--
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-- Returns:
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-- new instance
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new = function (self, obj) |
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obj = self:extend(obj) |
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if obj.onNew then obj:onNew() end |
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return obj |
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end, |
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-- Method: mixin
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-- Mixes all properties passed into the current object, overwriting any
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-- pre-existing values.
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--
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-- Arguments:
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-- obj - table of properties to mix into the object
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--
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-- Returns:
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-- current object
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mixin = function (self, obj) |
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assert(type(obj) == 'table', 'must mix in a table, received a ' .. type(obj)) |
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for key, value in pairs(obj) do |
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self[key] = obj[key] |
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end
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end, |
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-- Function: instanceOf
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-- Checks whether a certain object is anywhere in its inheritance chain.
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--
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-- Arguments:
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-- class - table to check against
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--
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-- Returns:
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-- boolean
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instanceOf = function (self, class) |
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local proto = self.prototype |
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while proto do |
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if proto == class then |
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return true |
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end
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proto = proto.prototype |
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end
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return false |
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end
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}
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