Looking for Struct Keys in Session - coldfusion

Question

I am trying to write a session helper and facing to problem to test if a Struct key in session exists?
I am trying like
<cffunction name="Exists" access="public" output="false" returntype="boolean" >
<cfargument name="Key" required="true" type="Any" />
<cfreturn Evaluate( "StructKeyExists( Session, #Arguments.Key# )" ) />
</cffunction>
Where I am calling the function like
<cfif Exists("data.fromdate") >
...
</cfif>
How should I write it?
Thanks

Answer 1

if you are checking to see if key "Test" exists in the session struct, try something like this:
<cffunction name="Exists" access="public" output="false" returntype="boolean" >
<cfargument name="Key" required="true" type="String" />
<cfreturn StructKeyExists(session, arguments.Key) />
</cffunction>
<cfif Exists("Test") >
....
</cfif>
Another concept, or two, since you are looking for a struct within the session would be:
<cffunction name="Exists" access="public" output="false" returntype="boolean" >
<cfargument name="Key" required="true" type="String" />
<cfreturn (structKeyExists(session, listFirst(arguments.Key,"."))
AND structKeyExists(session[listFirst(arguments.Key,".")], listLast(arguments.Key, "."))) />
</cffunction>
<cfif Exists("data.Test") >
....
</cfif>
and
<cffunction name="Exists" access="public" output="false" returntype="boolean" >
<cfargument name="struct" required="true" type="String" />
<cfargument name="Key" required="true" type="String" />
<cfreturn (structKeyExists(session, arguments.struct)
AND structKeyExists(session[arguments.struct], arguments.key)) />
</cffunction>
<cfif Exists("data", "Test") >
....
</cfif>
Hope all this helps point you in the right direction, good luck!

Answer 2

The following code will check any depth struct, and also correctly locks the Session scope.
<cffunction name="Exists" access="public" output="false" returntype="boolean">
<cfargument name="Key" required="true" type="string">
<cfset local.mainKeyList = ListChangeDelims(ListDeleteAt(Arguments.Key, ListLen(Arguments.Key, "."), "."), ",", ".")>
<cfset local.StructChain = "Session">
<cfloop list="#local.mainKeyList#" index="local.CurrentKey">
<cfset local.StructChain &= '["#local.CurrentKey#"]'>
</cfloop>
<cflock scope="session" type="readonly" timeout="3">
<cftry>
<cfset local.Exists = StructKeyExists(Evaluate(local.StructChain), ListLast(Arguments.Key, "."))>
<cfcatch>
<cfset local.Exists = false>
</cfcatch>
</cftry>
</cflock>
<cfreturn local.Exists>
</cffunction>
<cflock scope="session" type="exclusive" timeout="3">
<cfset Session.data.log.deep = "I'm here!">
</cflock>
<cfoutput>#Exists("data.log.deep")#</cfoutput>
Hopefully the amount of code in this function will justify why a helper function would be useful, to those pondering your reasons. This doesn't currently, but could be enhanced to, deal with Structs inside of Arrays as well. This also doesn't deal with an empty Arguments.Key, or fail gracefully on a cflock timeout, but should get you started.
Additionally, those that want to comment that cflock isn't required, please read the ColdFusion cflock docs first.
Simplified, but may provide inaccurate results in extremely rare conditions
Doing an IsDefined inline in your code will provide the opportunity for false positives, however having the IsDefined inside a udf or cfc method reduces this risk greatly to the point it may not need be a consideration. If you're happy to take that chance then you can simplify the function using IsDefined as Peter Boughton suggests.
<cffunction name="Exists" access="public" output="false" returntype="boolean">
<cfargument name="Key" required="true" type="string">
<cflock scope="session" type="readonly" timeout="3">
<cfset local.Exists = IsDefined("Session." & Arguments.Key)>
</cflock>
<cfreturn local.Exists>
</cffunction>

Answer 3

As Al Everett mentioned above, I don't remember the last time I had an app that didn't have session enabled. I guess if you can't be sure of that, then it makes sense to see if Session exists. My code for this would include:
<!--- in the application.cfc --->
<cffunction name="onSessionStart" output="false">
<!--- default session structure, you can also add default values to the data
structure here to ensure they exist later --->
<cfset session.data = {} />
</cffunction>
<!--- then in code use structKeyExists instead of a whole new function --->
<cfif structKeyExists(session.data, myKey)>
<!--- if you really wanted the "exists" function --->
<cffunction name="dataKeyExists" returntype="boolean" output="false">
<cfargument name="key" required="true" />
<cfreturn structKeyExists(session.data, arguments.key) />
</cffunction>
Depending on what's going on, I might choose to pass in the session to maintain encapsulation. But it doesn't always make sense to be a slave to OO and introduce complexity just for the sake of maintaining a pattern. Passing in the session structure and evaluating the key is really just a big workaround to using the "structKeyExists" function.
I also dislike having a function called "exists" because it tells me nothing about what it's really evaluating. I'd assume a function like that was like "isDefined" and more generic than just testing for a key in a specific structure.

Answer 4

<cfif structkeyexists(session, "data") and structkeyexists(session["data"], key)>
...
</cfif>

Answer 5

Why not just call <cfif isNull(session.data.fromdate)>
If the key data does not exist in session it will not throw, just returns false.