MACROMEDIA COLDFUSION MX 61-DEVELOPING COLDFUSION MX, Develop Manual

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48 Chapter 2: Elements of CFML
cfswitch, cfcase, and cfdefaultcase
The
cfswitch
,
cfcase
, and
cfdefaultcase
tags let you select among different code blocks
based on the value of an expression. ColdFusion processes these tags as follows:
1
The
cfswitch
tag evaluates an expression. The
cfswitch
tag body contains one or more
cfcase
tags and optionally includes
cfdefaultcase
tag.
2
Each
cfcase
tag in the
cfswitch
tag body specifies a value or set of values. If a value matches
the value determined by the expression in the
cfswitch
tag, ColdFusion runs the code in the
body of the
cfcase
tag and then exits the
cfswitch
tag. If two
cfcase
tags have the same
condition, ColdFusion generates an error.
3
If none of the
cfcase
tags match the value determined by the
cfswitch
tag, and the
cfswitch
tag body includes a
cfdefaultcase
tag, ColdFusion runs the code in the
cfdefaultcase
tag
body.
Note: Although the
cfdefaultcase
tag does not have to follow all
cfcase
tags, it is good programming
practice to put it at the end of the
cfswitch
statement.
The
cfswitch
tag provides better performance than a
cfif
tag with multiple
cfelseif
tags, and
is easier to read. Switch processing is commonly used when different actions are required based on
a a string variable such as a month or request identifier.
The following example shows switch processing:
<cfoutput query = "GetEmployees">
<cfswitch expression = #Department#>
<cfcase value = "Sales">
#FirstName# #LastName# is in <b>Sales</b><br><br>
</cfcase>
<cfcase value = "Accounting">
#FirstName# #LastName# is in <b>Accounting</b><br><br>
</cfcase>
<cfcase value = "Administration">
#FirstName# #LastName# is in <b>Administration</b><br><br>
</cfcase>
<cfdefaultcase>#FirstName# #LastName# is not in Sales,
Accounting, or Administration.<br>
</cfdefaultcase>
</cfswitch>
</cfoutput>
cfloop and cfbreak
The
cfloop
tag loops through the tag body zero or more times based on a condition specified by
the tag attributes. The
cfbreak
tag exits a
cfloop
tag.
cfloop
The
cfloop
tag provides five types of loops:
Loop type Description
Index Loops through the body of the tag and increments a counter variable by a
specified amount after each loop until the counter reaches a specified value.
Conditional Checks a condition and runs the body of the tag if the condition is True.
Query Loops through the body of the tag once for each row in a query.