Overhaul the concept of lua 'class' initialization yet again.
Alexander Gavrilov
parent
a7998f71a2
commit
57b72831ca
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-- A trivial reloadable class system
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local _ENV = mkmodule('class')
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-- Metatable template for a class
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class_obj = {} or class_obj
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-- Methods shared by all classes
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common_methods = {} or common_methods
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-- Forbidden names for class fields and methods.
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reserved_names = { super = true, ATTRS = true }
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-- Attribute table metatable
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attrs_meta = {} or attrs_meta
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-- Create or updates a class; a class has metamethods and thus own metatable.
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function defclass(class,parent)
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class = class or {}
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local meta = getmetatable(class)
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if not meta then
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meta = {}
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setmetatable(class, meta)
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end
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for k,v in pairs(class_obj) do meta[k] = v end
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meta.__index = parent or common_methods
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local attrs = rawget(class, 'ATTRS') or {}
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setmetatable(attrs, attrs_meta)
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rawset(class, 'super', parent)
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rawset(class, 'ATTRS', attrs)
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rawset(class, '__index', rawget(class, '__index') or class)
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return class
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end
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-- An instance uses the class as metatable
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function mkinstance(class,table)
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table = table or {}
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setmetatable(table, class)
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return table
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end
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-- Patch the stubs in the global environment
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dfhack.BASE_G.defclass = _ENV.defclass
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dfhack.BASE_G.mkinstance = _ENV.mkinstance
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-- Just verify the name, and then set.
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function class_obj:__newindex(name,val)
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if reserved_names[name] or common_methods[name] then
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error('Method name '..name..' is reserved.')
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end
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rawset(self, name, val)
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end
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function attrs_meta:__call(attrs)
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for k,v in pairs(attrs) do
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self[k] = v
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end
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end
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local function apply_attrs(obj, attrs, init_table)
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for k,v in pairs(attrs) do
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if v == DEFAULT_NIL then
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v = nil
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end
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obj[k] = init_table[k] or v
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end
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end
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local function invoke_before_rec(self, class, method, ...)
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local meta = getmetatable(class)
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if meta then
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local fun = rawget(class, method)
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if fun then
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fun(self, ...)
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end
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invoke_before_rec(self, meta.__index, method, ...)
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end
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end
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local function invoke_after_rec(self, class, method, ...)
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local meta = getmetatable(class)
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if meta then
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invoke_after_rec(self, meta.__index, method, ...)
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local fun = rawget(class, method)
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if fun then
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fun(self, ...)
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end
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end
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end
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local function init_attrs_rec(obj, class, init_table)
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local meta = getmetatable(class)
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if meta then
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init_attrs_rec(obj, meta.__index, init_table)
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apply_attrs(obj, rawget(class, 'ATTRS'), init_table)
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end
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end
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-- Call metamethod constructs the object
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function class_obj:__call(init_table)
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-- The table is assumed to be a scratch temporary.
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-- If it is not, copy it yourself before calling.
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init_table = init_table or {}
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local obj = mkinstance(self)
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-- This initialization sequence is broadly based on how the
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-- Common Lisp initialize-instance generic function works.
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-- preinit screens input arguments in subclass to superclass order
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invoke_before_rec(obj, self, 'preinit', init_table)
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-- initialize the instance table from init table
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init_attrs_rec(obj, self, init_table)
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-- init in superclass -> subclass
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invoke_after_rec(obj, self, 'init', init_table)
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-- postinit in superclass -> subclass
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invoke_after_rec(obj, self, 'postinit', init_table)
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return obj
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end
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-- Common methods for all instances:
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function common_methods:callback(method, ...)
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return dfhack.curry(self[method], self, ...)
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end
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function common_methods:assign(data)
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for k,v in pairs(data) do
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self[k] = v
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end
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end
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function common_methods:invoke_before(method, ...)
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return invoke_before_rec(self, getmetatable(self), method, ...)
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end
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function common_methods:invoke_after(method, ...)
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return invoke_after_rec(self, getmetatable(self), method, ...)
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end
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return _ENV
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