MACROMEDIA COLDFUSION MX 61-DEVELOPING COLDFUSION MX, Develop Manual

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About scopes 77
Using scopes
The following sections provide details on how you can create and use variables in different scopes.
Evaluating unscoped variables
If you use a variable name without a scope prefix, ColdFusion checks the scopes in the following
order to find the variable:
1
Arguments
2
Variables (local scope)
3
CGI
4
Cffile
5
URL
6
Form
7
Cookie
8
Client
Because ColdFusion must search for variables when you do not specify the scope, you can
improve performance by specifying the scope for all variables.
To access variables in all other scopes, you must prefix the variable name with the scope identifier.
Scopes and CFX tags
ColdFusion scopes do not apply to ColdFusion Extension (CFX) tags, custom tags that you write
in a programming language such as C++ or Java. The ColdFusion page that calls a CFX tag must
use tag attributes to pass data to the CFX tag. The CFX tag must use the Java Request and
Response interfaces or the C++ Request class to get and return data.
The Java
setVariable
Response interface method and C++
CCFX::SetVariable
method return
data to the Variables scope of the calling page. Therefore, they are equivalent to setting a Caller
scope variable in a custom ColdFusion tag.
Using scopes as structures
ColdFusion makes all named scopes available as structures. You cannot access the function-local
scope for user defined functions (UDFs) that you define using CFScript as a structure. (In
ColdFusion 4.5 and 5, the following scopes are
not available as structures: Variables, Caller,
Client, and Server.)
You can reference the variables in named scopes as elements of a structure. To do so, specify the
scope name as the structure name and the variable name as the key. For example, if you have a
MyVar variable in the Request scope, you can refer to it in either of the following ways:
Request.MyVar
Request["MyVar"]
Similarly, you can use CFML structure functions to manipulate the contents of the scope. For
more information on using structures, see
Chapter 5, “Using Arrays and Structures,”
on page 103 .