Lua脚本和redis - 如何测试None值(Lua script and redis - how to test for None value)

 以下是我的lua脚本： 
 
     local ckid = redis.pcall('get',KEYS[1])
     local meta = redis.call('hgetall', ckid)
     return {ckid, meta}
 
 如果密钥没有退出第一个电话，我不想执行第二个。 
 
 所以......我没有什么是没有回报的价值。 在python中，返回值是None。 
 
if ckid ~= '???????' then 
    local meta = redis.call('hgetall', ckid)
else
     local meta = 'empty'
retrun {ckid, meta}
 
 所以...我怎么做这个是lua？ 
 
     local ckid = redis.pcall('get',KEYS[1])
     if ckid ~= nil then
         local meta = redis.call('hgetall', ckid)
     else
         local meta = 'none'
         local ckid = 'none'
     end

     return {ckid, meta}
 
 当使用零.. 
 
ResponseError: ERR Error running script (call to f_1400713412b0063a26eb0dc063f53a4e3be26380): user_script:12: Script attempted to access unexisting global variable 'meta'

Below is my lua script:
 
     local ckid = redis.pcall('get',KEYS[1])
     local meta = redis.call('hgetall', ckid)
     return {ckid, meta}
 
if the key does not exits for the first call I would not like to execute the second.
 
So...I don't what the return value is for None. In python the return value would be None.
 
if ckid ~= '???????' then 
    local meta = redis.call('hgetall', ckid)
else
     local meta = 'empty'
retrun {ckid, meta}
 
So...how do I do this is lua?
 
     local ckid = redis.pcall('get',KEYS[1])
     if ckid ~= nil then
         local meta = redis.call('hgetall', ckid)
     else
         local meta = 'none'
         local ckid = 'none'
     end

     return {ckid, meta}
 
When using nil..
 
ResponseError: ERR Error running script (call to f_1400713412b0063a26eb0dc063f53a4e3be26380): user_script:12: Script attempted to access unexisting global variable 'meta'

原文：https://stackoverflow.com/questions/13206613