Why is this set? is it like cfparam for components?

[Hydrowizard]

In the docs this line is used:
<cfset var empQuery="">
which seems to be creating a cfparam like variable in case the empQuery is not defined? Is that about right?
Why is this needed(is it even needed?)
Thanks

[Newsgroup_User]

Hydrowizard wrote:
> In the docs this line is used:
> <cfset var empQuery="">
> which seems to be creating a cfparam like variable in case the empQuery is not
> defined? Is that about right?

not really, it scopes the variable to one local (the "var" bit) to that function
so it won't get mixed up w/other calls to that function/cfc which can happen
under a load. something like the query gets finished but in the span of time
before it's returned, another call is made to that function & maybe the
resultset is different (not in this case bu you see where this is going). the
first call to that function could return the 2nd call's results. scoping that
variable local prevents this from happening.

[Hydrowizard]

Thanks Paul so best practise means that I should use it. It is a bit like cfttransaction in the reasons whjy it is needed thanks again

[Newsgroup_User]

It is more like a strongly typed language where one has to initialize
ones variables before one can use them. In CF this initializes the
variable so that it is local to the function, otherwise the variable
will be global and if one does not account for the global nature, very
hard to track bugs can be introduced into the code.

The best practice is to ALWAYS initialize local variable and to ALWAYS
scope variables so that is is explicit when one is using local and one
is using global 'variables' scoped variables.


<cffunction...>
...
<cfset var myLocalVar = ...><!--- initializes a local var --->
<cfset variables.myGlobalVar = ...> <!--- initializes a global var --->

<cfsomething myLocalVar ...><!--- uses the local var --->

<cfsomethingelse variables.myGlobalVar...><!--- uses the global var --->

[Hydrowizard]

Thanks Ian for explaining that-last question what is 'initializes' in laymans terms? Cheers

this all reminds me of the complexity of learning how to do cfif equivalents in cfscript!

[Newsgroup_User]

Hydrowizard wrote:
> Thanks Ian for explaining that-last question what is 'initializes' in laymans terms? Cheers
>
> this all reminds me of the complexity of learning how to do cfif equivalents in cfscript!

In strongly typed languages like Java and C++, before one can use a
variable one must initialize it. I.E. one must name it; define the type
of variable, integer, string, float, etc., its scope, global, package,
local, etc.

ColdFusion is generally a loosely typed language and does not require
this rigid definition. But when one starts working with code that can
be used repeatedly in the same space, typing becomes more important. So
it is a best practice to type ones variables in a function to keep the
code easier to work with.

[BKBK]

One other advantage of using var: since it is local to the function, empQuery will be marked for garbage collection once the function returns.

[Hydrowizard]

Thanks for all those replies really appreciated that makes sense-now back to the docs!

[Amiable_Penguin15D5]

I've got a series on OOP with CF that addresses the questions you had and more.

Object Oriented Coldfusion : 1 : Intro to Object.cfc

Object Oriented Coldfusion : 4 : The var scope