On Friday, Jan 24, 2003, at 06:56 US/Pacific, Jon Gunnip wrote:
> I am writing UDF's on MX using <cffunction>, and I would like to know
> what
> the best way to create local variables for use inside my functions
> that will
> not interfere with variables in the caller's scope.
As others have said - use "var". One practice that many people seem to
like (and about which I'm still on the fence) is to declare a "local"
struct and use that throughout:
> <cffunction name="add_two_numbers">
> <cfargument name="first" required="true">
> <cfargument name="second" required="true">
<cfset var local = structNew()>
> <cfset local.sum=arguments.first + arguments.second>
> <cfreturn local.sum>
> </cffunction>
This has the nice side effect that you only need one "var" declaration
at the top of your function and all subsequent local.xxx references are
safe from "outside influence".
It has the downside that you end up doing a struct dereference for
every local variable.
Note that if you had your original code inside a CFC, the unadorned
"sum" variable would become a private (OK, 'protected') instance
variable inside the component instance and not accessible from outside.
See below:
> <!--- page that uses the function --->
> <cfinclude template="functions.cfm">
Becomes:
<cfset adder = createObject("component","adder")>
> <!--- using sum to track addition of numbers --->
> <cfset sum=12>
>
> <!--- sum is now 12 --->
> <cfset result=add_two_numbers(1, 2)>
Becomes:
<cfset result = adder.add_two_numbers(1, 2)>
> <!--- sum is now 3 (changed in function), when I want it to be 12 --->
No longer true - unadorned "sum" is protected inside CFC.
> <cfset sum=sum + result>
> <!--- sum is now 6, when I want it to be 15 --->
sum would be 15.
Sean A Corfield -- Director, Architecture
Web Technology Group -- Macromedia, Inc.
tel: (415) 252-2287 -- cell: (415) 717-8473
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