MACROMEDIA COLFUSION MX 7-CFML, Справочник

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654 Chapter 3: ColdFusion Functions
Note: If you use number signs (#) in string_expression1 or string_expression2, ColdFusion evaluates
the part of the expression in number signs first. If you misuse the number signs, you can cause
unexpected results from the
IIf
function. For example, if you use number signs around the whole
expression in string_expression1, and if there is an undefined variable in string_expression1, the
function might fail, with the error 'Error Resolving Parameter,'
If a variable is undefined, ColdFusion throws an error when it processes this function. The
following example shows this problem:
#IIf(IsDefined("Form.Deliver"), DE(Form.Deliver), DE("no"))#
This returns "Error resolving parameter FORM.DELIVER".
To avoid this problem, use the
DE
and
Evaluate
functions in code such as the following:
#IIf(IsDefined("Form.Deliver"), Evaluate(DE("Form.Deliver")), DE("no"))#
This returns "no"; ColdFusion does not throw an error.
In the following example,
LocalVar
is undefined; however, if you omit number signs around
LocalVar
, the code works properly:
<cfoutput>
#IIf(IsDefined("LocalVar"), "LocalVar",
DE("The variable is not defined."))#
</cfoutput>
The output is:
The variable is not defined.
The number signs around
LocalVar
in the following code cause it to fail with the error message
'Error Resolving Parameter', because ColdFusion never evaluates the original condition
IsDefined("LocalVar")
.
Here is another example:
<cfoutput>
#IIf(IsDefined("LocalVar"), DE("#LocalVar#"), DE("The variable is not
defined."))#
</cfoutput>
The error message would be as follows:
Error resolving parameter LOCALVAR
The
DE
function has no effect on the evaluation of
LocalVar
, because the number signs cause it to
be evaluated immediately.
Example
<h3>IIf Function Example</h3>
<p>IIf evaluates a condition, and does an Evaluate on string
expression 1 or string expression 2 depending on the Boolean
outcome <I>(True: run expression 1; False: run expression 2)</I>.</p>
<p>The result of the expression
IIf( Hour(Now()) GTE 12,
DE("It is afternoon or evening"),
DE("It is morning"))
is:<br><b>