为什么没有定义参数，如果我可以转储它，它在Coldfusion有一个值？ [英] Why a parameter is not defined, if I can dump it and it has a value in Coldfusion?

问题描述

只是有点无知...使用Coldfusion8，如果我转储我的会话到文件：

 < cfdump output = D：\ColdFusion8\logs\dump.txtvar =＃Session＃> 
  

这包括：

  accounttyp：whatever 
  

如果我只转储这个参数，

 < cfdump output =D：\ColdFusion8\logs\dump.txtvar =＃Session。 accounttyp＃> 
  

问题：

如果定义并转储可以检查 isDefined ：

 < cfdump output =D： \\ColdFusion8\logs\dump.txtvar =＃IsDefined（Session.accounttyp）＃> 
  

原来是否？如果它在那里应该定义，应该不是吗？

感谢您的澄清。

解决方案

< cfdump output =D：\ColdFusion8\logs\dump.txt
var =＃IsDefined （Session.accounttyp）＃>

这是因为语法不正确。 IsDefined 期望变量的名称，即字符串。通过忽略变量名引号，会话变量首先被计算，其值（whatever）被传递到 IsDefined 。所以代码实际上是检查一个名为whatever，而不是session.accounttyp的变量，即：

 < cfif IsDefined （whatever）> 
  

这就是为什么结果是 NO 。这是正确的语法。 （注意引号和缺少磅符号）。

 < cfif IsDefined（Session.accounttyp）&但是，我建议切换到 structKeyExists    。通常优先于 IsDefined ，因为它更精确。
 
Just a little clueless... using Coldfusion8, if I dump my session to file:
<cfdump output="D:\ColdFusion8\logs\dump.txt" var="#Session#">
this includes:
accounttyp: whatever
I get the same result if I only dump this parameter:
<cfdump output="D:\ColdFusion8\logs\dump.txt" var="#Session.accounttyp#">
Question:

If it's defined and dump-able, how come checking isDefined like so: 
<cfdump output="D:\ColdFusion8\logs\dump.txt" var="#IsDefined(Session.accounttyp)#"> 
turns out to be NO? If it's there it should be defined, shouldn't it?

Thanks for some clarification.
解决方案

  
<cfdump output="D:\ColdFusion8\logs\dump.txt"
  var="#IsDefined(Session.accounttyp)#">
It is because the syntax is incorrect. IsDefined expects the name of a variable ie a string. By omitting the quotes around the variable name, the session variable gets evaluated first, and its value ("whatever") is what gets passed into IsDefined. So the code is actually checking for a variable named "whatever", not "session.accounttyp" ie:
    <cfif IsDefined("whatever")>
That is why the result is NO. This is the correct syntax. (Notice the quotes and lack of pound signs).
    <cfif IsDefined("Session.accounttyp")>
However, I would suggest switching to structKeyExists. It is generally preferred over IsDefined because it is more precise.

                        
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