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Diffstat (limited to 'library/lua/class.lua')
| -rw-r--r-- | library/lua/class.lua | 150 |
1 files changed, 150 insertions, 0 deletions
diff --git a/library/lua/class.lua b/library/lua/class.lua new file mode 100644 index 00000000..7b142e49 --- /dev/null +++ b/library/lua/class.lua @@ -0,0 +1,150 @@ +-- A trivial reloadable class system + +local _ENV = mkmodule('class') + +-- Metatable template for a class +class_obj = {} or class_obj + +-- Methods shared by all classes +common_methods = {} or common_methods + +-- Forbidden names for class fields and methods. +reserved_names = { super = true, ATTRS = true } + +-- Attribute table metatable +attrs_meta = {} or attrs_meta + +-- Create or updates a class; a class has metamethods and thus own metatable. +function defclass(class,parent) + class = class or {} + + local meta = getmetatable(class) + if not meta then + meta = {} + setmetatable(class, meta) + end + + for k,v in pairs(class_obj) do meta[k] = v end + + meta.__index = parent or common_methods + + local attrs = rawget(class, 'ATTRS') or {} + setmetatable(attrs, attrs_meta) + + rawset(class, 'super', parent) + rawset(class, 'ATTRS', attrs) + rawset(class, '__index', rawget(class, '__index') or class) + + return class +end + +-- An instance uses the class as metatable +function mkinstance(class,table) + table = table or {} + setmetatable(table, class) + return table +end + +-- Patch the stubs in the global environment +dfhack.BASE_G.defclass = _ENV.defclass +dfhack.BASE_G.mkinstance = _ENV.mkinstance + +-- Just verify the name, and then set. +function class_obj:__newindex(name,val) + if reserved_names[name] or common_methods[name] then + error('Method name '..name..' is reserved.') + end + rawset(self, name, val) +end + +function attrs_meta:__call(attrs) + for k,v in pairs(attrs) do + self[k] = v + end +end + +local function apply_attrs(obj, attrs, init_table) + for k,v in pairs(attrs) do + if v == DEFAULT_NIL then + v = nil + end + obj[k] = init_table[k] or v + end +end + +local function invoke_before_rec(self, class, method, ...) + local meta = getmetatable(class) + if meta then + local fun = rawget(class, method) + if fun then + fun(self, ...) + end + + invoke_before_rec(self, meta.__index, method, ...) + end +end + +local function invoke_after_rec(self, class, method, ...) + local meta = getmetatable(class) + if meta then + invoke_after_rec(self, meta.__index, method, ...) + + local fun = rawget(class, method) + if fun then + fun(self, ...) + end + end +end + +local function init_attrs_rec(obj, class, init_table) + local meta = getmetatable(class) + if meta then + init_attrs_rec(obj, meta.__index, init_table) + apply_attrs(obj, rawget(class, 'ATTRS'), init_table) + end +end + +-- Call metamethod constructs the object +function class_obj:__call(init_table) + -- The table is assumed to be a scratch temporary. + -- If it is not, copy it yourself before calling. + init_table = init_table or {} + + local obj = mkinstance(self) + + -- This initialization sequence is broadly based on how the + -- Common Lisp initialize-instance generic function works. + + -- preinit screens input arguments in subclass to superclass order + invoke_before_rec(obj, self, 'preinit', init_table) + -- initialize the instance table from init table + init_attrs_rec(obj, self, init_table) + -- init in superclass -> subclass + invoke_after_rec(obj, self, 'init', init_table) + -- postinit in superclass -> subclass + invoke_after_rec(obj, self, 'postinit', init_table) + + return obj +end + +-- Common methods for all instances: + +function common_methods:callback(method, ...) + return dfhack.curry(self[method], self, ...) +end + +function common_methods:assign(data) + for k,v in pairs(data) do + self[k] = v + end +end + +function common_methods:invoke_before(method, ...) + return invoke_before_rec(self, getmetatable(self), method, ...) +end + +function common_methods:invoke_after(method, ...) + return invoke_after_rec(self, getmetatable(self), method, ...) +end + +return _ENV |
