Lua实现继承

感觉Lua用起来很奇怪，但也得慢慢适应这种变化：

-- base class
Window = {
    x = 0,
    y = 0,
    height = 0,
    width = 0,

    display = function(self)
        print('Window', x, y, height, width)
    end
}

-- structure function
function Window:new(o)
    o = o or {}
    setmetatable(o, self)
    self.__index = self;
    return o
end

-- extend
function Window:extend()
    o = {}
    setmetatable(o, self)
    self.__index = self;
    return o
end

-- MyWindow
MyWindow = Window:extend()

-- override
function MyWindow:display()
    print('MyWindow', self.x, self.y, self.height, self.width)
end

-- new MyWindow
s = MyWindow:new{x=1,y=1,height=800,width=600}
s:display()