Lua 基础

注释

-- 单行

--[[
多行
...
--]]

基本类型和类型判断

print(type("Hello world"))      --> string
print(type([[ hello world ]]))  --> string, 块字符串
print(type(10.4*3))             --> number
print(type(print))              --> function
print(type(type))               --> function
print(type(true))               --> boolean
print(type(nil))                --> nil
print(type(type(1)))            --> string
print(type({}))                 --> table


if 0 then print("then") end     --> then, 0 == true

local a = 1;
assert(type(a) == "number");
assert(type(c) == "nil" );
assert(c == nil);

string:

assert(1+1 == 2)
assert("1"+1 == 2)
assert("1"+"1" == 2)
assert("a".."b" == "ab") -- 字符串拼接
assert(#"ajanuw" == 6)  -- 长度

function:

-- 没有返回值
local function f1(name)
  print("hello "..name)
end

-- 返回一个参数
local function f2(name)
 return "hello "..name
end

-- 返回多个参数
local function f3(name)
  return "hello "..name,1,2
 end

 f1("ajanuw")
 print(f2("ajanuw"))

 local a,b,c = f3("ajanuw")
 print(a..b..c)

 -- 将函数赋值给变量
 f4 = f1
 f4("f4")

 -- 清理函数
f4 = nil
assert(f4 == nil)

-- 可变参数
local function f1(...)
 print(#{...}) -- 3

 for i,v in ipairs{...} do
   print(i, v)
 end
end

f1(1,2,3)

回调函数

local function f1(name, cb)
  cb(name)
end

f1("ajanuw", function(name)
  print("hello "..name)
end
)

循环

i = 10
while( i >= 0 )
do
   print(i)
   i = i-1
end

--  init    end  step
for i = 10, 0,   -1 
do
  print(i) -- 10 .. 0
end

if判断

a = 3
if a == nil then
  print(1)
elseif a == 1 then
  print(2)
else 
  print(3)
end

数组

-- 索引从1开始
array = {1, "string.."}

for i = 1, #array do
   print(array[i])
end

-- 迭代器
for i,v in ipairs(array) do
  print(v)
end

table

local _table = {}

-- 增
_table[1] = 1
_table['key1'] = "value1"

-- 删
_table[1] = nil

-- 改
_table['key1'] = "value11"

-- 查
print(_table['key1'])

-- 迭代
for k,v in pairs(_table) do
  print(k .. " : " .. v)
end

模块

创建

hello = {}

hello.version = '0.0.1'

function hello.echo(name) 
  print("hello " .. name)  
end

hello.echo2 = function (name) 
  print("hello " .. name)  
end

-- 导出
return hello

使用

local hello = require "hello"

print(hello.version)
hello.echo("ajanuw")
hello.echo2("ajanuw2")

文件io

-- 追加的方式读写文件，不存在自动创建
hFile = io.open ("a.ini" ,"a+")

-- 设置输出句柄，然后写入
io.output(hFile)
io.write("hello\r\n")
io.write("word\r\n")

io.close(hFile) -- 关闭


hFile = io.open ("a.ini" ,"a+")
io.input(hFile)  -- 设置输入句柄
print(io.read('*a')) -- 读取整个文件
io.close(hFile)

class

Klass = {
  name = "",
  age = 0
}

function Klass:new(name, age)
  local o = {name = name, age = age}
  setmetatable(o, {__index = Klass})
  return o
end

function Klass:hello()
  print("hello " .. self.name)
end

k = Klass:new("ajanuw",11)
print(k.name)
k:hello()

print('------------------------------------')

-- 继承 Klass
Klass2 = Klass:new()
function Klass2:new(name,age)
  local o = Klass:new(name,age)
  setmetatable(o, { __index = self })
  return o
end

function Klass2:h()
  self:hello()
end


k2 = Klass2:new("ajanuw2",11)
print(k2.name)
k2:h()