User Guide

Working with arguments and variables in functions 185
Function-only variables
In addition to the Arguments scope, each function can have a number of variables that exist only
inside the function, and are not saved between times the function gets called. As soon as the
function exits, all the variables in this scope are removed.
In CFScript, you create function-only variables with the
var statement. Unlike other variables,
you never prefix function-only variables with a scope name.
Using function-only variables
Make sure to use the
var statement in CFScript UDFs to declare all function-specific variables,
such as loop indexes and temporary variables that are required only for the duration of the
function call. Doing this ensures that these variables are available inside the function only, and
makes sure that the variable names do not conflict with the names of variables in other scopes. If
the calling page has variables of the same name, the two variables are independent and do not
affect each other.
For example, if a ColdFusion page has a
cfloop tag with an index variable i, and the tag body
calls a CFScript UDF that also has a loop with a function-only index variable i, the UDF does not
change the value of the calling page loop index, and the calling page does not change the UDF
index. So you can safely call the function inside the
cfloop tag body.
In general, use the
var statement to declare all UDF variables, other than the function arguments
or shared-scope variables, that you use only inside CFScript functions. Use another scope,
however, if the value of the variable must persist between function calls; for example, for a counter
that the function increments each time it is called.
Referencing caller variables
A function can use and change any variable that is available in the calling page, including variables
in the caller’s Variables (local) scope, as if the function was part of the calling page. For example, if
you know that the calling page has a local variable called Customer_name (and there is no
function scope variable named Customer_name) the function can read and change the variable by
referring to it as Customer_name or (using better coding practice) Variables.Customer_name.
Similarly, you can create a local variable inside a function and then refer to it anywhere in the
calling page after the function call. You cannot refer to the variable before you call the function.
However, you should generally avoid using the caller’s variables directly inside a function. Using
the caller’s variables creates a dependency on the caller. You must always ensure that the code
outside the function uses the same variable names as the function. This can become difficult if
you call the function from many pages.
You can avoid these problems by using only the function arguments and the return value to pass
data between the caller and the function. Do not reference calling page variables directly in the
function. As a result, you can use the function anywhere in an application (or even in multiple
applications), without concern for the calling code’s variables.