Lua类的实现

旧城等待， 2022-07-13 13:56 170阅读 0赞

详细参见：[lua class wiki][]和[lua class github][]

-- class.lua
    -- Compatible with Lua 5.1 (not 5.0).
    function class(base, init)
       local c = {}    -- a new class instance
       if not init and type(base) == 'function' then
          init = base
          base = nil
       elseif type(base) == 'table' then
        -- our new class is a shallow copy of the base class!
          for i,v in pairs(base) do
             c[i] = v
          end
          c._base = base
       end
       -- the class will be the metatable for all its objects,
       -- and they will look up their methods in it.
       c.__index = c
    
       -- expose a constructor which can be called by <classname>(<args>)
       local mt = {}
       mt.__call = function(class_tbl, ...)
       local obj = {}
       setmetatable(obj,c)
       if init then
          init(obj,...)
       else 
          -- make sure that any stuff from the base class is initialized!
          if base and base.init then
          base.init(obj, ...)
          end
       end
       return obj
       end
       c.init = init
       c.is_a = function(self, klass)
          local m = getmetatable(self)
          while m do 
             if m == klass then return true end
             m = m._base
          end
          return false
       end
       setmetatable(c, mt)
       return c
    end

require 'class'
    
    Animal = class(function(a,name)
       a.name = name
    end)
    
    function Animal:__tostring()
      return self.name..': '..self:speak()
    end
    
    Dog = class(Animal)
    
    function Dog:speak()
      return 'bark'
    end
    
    Cat = class(Animal, function(c,name,breed)
             Animal.init(c,name)  -- must init base!
             c.breed = breed
          end)
    
    function Cat:speak()
      return 'meow'
    end
    
    Lion = class(Cat)
    
    function Lion:speak()
      return 'roar'
    end
    
    fido = Dog('Fido')
    felix = Cat('Felix','Tabby')
    leo = Lion('Leo','African')
    D:\Downloads\func>lua -i animal.lua
    > = fido,felix,leo
    Fido: bark      Felix: meow     Leo: roar
    > = leo:is_a(Animal)
    true
    > = leo:is_a(Dog)
    false
    > = leo:is_a(Cat)
    true

[lua class wiki]: http://lua-users.org/wiki/SimpleLuaClasses
[lua class github]: https://github.com/goulu/GLua/blob/master/src/class.lua