先来看一段简单的代码:
local Animal = {} function Animal:Eat( food ) print("Animal:Eat", self, food) end function Animal.Sleep( time ) print("Animal.Sleep", self, time) end Animal:Eat("grass") Animal.Eat("grass") Animal:Sleep(1) Animal.Sleep(1)
输出结果为:
Animal:Eat table: 0x7f8421c07540 grass Animal:Eat grass nil Animal.Sleep nil table: 0x7f8421c07540 Animal.Sleep nil 1
由此可见,
定义:
在Eat(冒号函数)内部有一个参数self,在Sleep(点函数)内部没有参数self;
调用:
用冒号(:)调用函数时,会默认传一个值(调用者自身)作为第一个参数;
用点(.)调用函数时,则没有;
-- 如果要使结果一致,则:
Animal:Eat("grass") Animal.Eat(Animal,"grass") Animal:Sleep() Animal.Sleep(Animal)
输出结果:
Animal:Eat table: 0x7f8421c07540 grass Animal:Eat table: 0x7f8421c07540 grass Animal.Sleep nil table: 0x7f8421c07540 Animal.Sleep nil table: 0x7f8421c07540
-- 我们为什么可以用.和:来定义函数
function Animal.Sleep( time ) end
-- 这种写法是一种语法糖(syntactic sugar),它的原型是:
Animal.Sleep = function ( time ) end
用双冒号(:)时,也是一种语法糖,实际上默认传递一个self(Animal)参数:
function Animal:Eat( food ) end
等价于
function Animal.Eat( self, food ) end
可参考Lua函数定义:
http://www.lua.org/manual/5.2/manual.html#pdf-next
3.4.10 – Function Definitions
The syntax for function definition is
functiondef ::= function funcbody funcbody ::= ‘(’ [parlist] ‘)’ block endThe following syntactic sugar simplifies function definitions:
stat ::= function funcname funcbody stat ::= local function Name funcbody funcname ::= Name {‘.’ Name} [‘:’ Name]The statement
function f () body endtranslates to
f = function () body endThe statement
function t.a.b.c.f () body endtranslates to
t.a.b.c.f = function () body endThe statement
local function f () body endtranslates to
local f; f = function () body endnot to
local f = function () body end
时间: 2024-11-05 11:33:53