处理空值与JSON返回

Question

我运行红宝石1.9。我有这个代码，它是从这两个/usr/sbin/storcli /c0/bbu show j & /usr/sbin/storcli /c0/cv show j命令中提取出Status和State的值。

#!/usr/bin/ruby 
require 'json' 

output_bbu = %x{/usr/sbin/storcli /c0/bbu show j} 
output_cv = %x{/usr/sbin/storcli /c0/cv show j} 

begin 
     j = JSON.parse(output_bbu) 
     k = JSON.parse(output_cv) 
     result = j["Controllers"][0]["Command Status"]["Status"] 

     ### I'm not sure how to get the value of "State" and store it in "status" variable. 

     status = k["Controllers"][0]["Response Data"]["Cachevault_Info"][0]["State"] 
     status = j["Controllers"][0]["Response Data"]["BBU_Info"][0]["State"] 

     ### 
rescue Exception => e 
     puts "CRITICAL: error reading BBU status: #{e}" 
     exit 2 
end 

if result != 'Success' 
     puts "CRITICAL: command not successful, result: #{result}" 
     exit 2 
end 

问题：

其中两个命令storcli /c0/cv show j或storcli /c0/bbu show j在 “状态” 返回空值的变量和脚本失败，错误

未定义的方法`[]”为无：NilClass

storcli /c0/cv show j co uld返回“State”的零值或storcli /c0/bbu show j可返回零。所以我想要做的是将“状态”的值存储在变量“状态”中。命令

示例输出，

$ storcli /c0/cv show j 

{ 
"Controllers":[ 
{ 
     "Command Status" : { 
       "Controller" : 0, 
       "Status" : "Success", 
       "Description" : "None" 
     }, 
     "Response Data" : { 
       "Cachevault_Info" : [ 
         { 
           "Model" : "CVPM02", 
           "State" : "Optimal", 
           "Temp" : "35C", 
           "Mode" : "-", 
           "MfgDate" : "2013/09/17" 
         } 
       ] 
     } 
} 
] 
} 

看，这里它返回“状态”为“最佳”的价值，所以我想它的值存储在变量“的地位。”

零的示例输出，

$ storcli /c0/bbu show j 

{ 
"Controllers":[ 
{ 
     "Command Status" : { 
       "Controller" : 0, 
       "Status" : "Failure", 
       "Description" : "None", 
       "Detailed Status" : [ 
         { 
           "Ctrl" : 0, 
           "Status" : "Failed", 
           "Property" : "-", 
           "ErrMsg" : "use /cx/cv", 
           "ErrCd" : 1001 
         } 
       ] 
     } 
} 
] 
} 

Answer 1

既然你不是从一个命令得到一个“响应数据”，您可以使用下面的

status = k["Controllers"][0] 
      .fetch(["Response Data"], {}) 
      .fetch(["Cachevault_Info"], {}) 
      .fetch([0], {})["Status"] 
status ||= j["Controllers"][0]["Response Data"]["BBU_Info"][0]["State"] 

随着||=，如果结果from status = k是nil它会设置为status = j