Introduction to ColdFusion Markup Language - The cfswitch tag
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ColdFusion also has another conditional logic mechanism that is usually more efficient and results in more modular and easy-to-read code: the<cfswitch>tag. We could change the series ofif ...statements in the first "thisMonth" <cfif> example into the followingswitchstatement (seecfswitch.cfmin the books downloadable code):
<cfset thisMonth = 1>
<cfswitch expression="#thisMonth#">
<cfcase value="1">
It is January.
</cfcase>
<cfcase value="2">
It is February.
</cfcase>
<cfcase value="3">
It is March.
</cfcase>
<cfdefaultcase>
It is some other month.
</cfdefaultcase>
</cfswitch>
If you replace the code from the previous example with this, then you will also seeIt is January.in the browser window.
The expression in the<cfswitch>tag is executed only once, and ColdFusion tries to match the expression to a case. If ColdFusion finds no cases that match, it executes the optional<cfdefaultcase>block if it is present. The<cfdefaultcase>acts as the<cfelse>statement did previously. Once ColdFusion finds a matching<cfcase>statement, it skips over the remaining<cfcase>and<cfdefaultcase>blocks. The case statement also accepts a list of comma-separated values, which allows us to say "If the value is X, Y, or Z, then do this."
Here's an example of this (defaultcase.cfm):
<cfset thisMonth = 1>
<cfswitch expression="#thisMonth#">
<cfcase value="1,2,3">
It is January, February or March.
</cfcase>
<cfcase value="4,5,6">
It is April, May or June.
</cfcase>
<cfdefaultcase>
It is something else.
</cfdefaultcase>
</cfswitch>
The preceding code block does the following: if#thisMonth#is 1, 2, or 3, then the first case will match and the code block will be executed. Otherwise, the<cfswitch>keeps trying to match the value of#thisMonth#to the values listed within the<cfcase>tags until it finds a match or encounters the<cfdefaultcase>tag.
There is one important difference between using a series of<cfif>statements and a<cfswitch>statement. We can test for multiple expressions by using a<cfif>statement by separating them with anANDorORkeyword.
<cfif (IsDefined("Url.Name")) AND (Url.Name EQ "Larry")>
...
<cfelseif (IsDefined("Url.Number")) AND (Url.Number EQ 7)>
...
</cfif>
This behavior isn't possible using<cfswitch, which can evaluate only a single expression and match a value or series of values, so it isn't always possible to rewrite a<cfif>block as a<cfswitch>. You can also see that, because you are comparing the value ofUrl.Nameto a string, you do need to enclose the string in a pair of quotes.
Next: The cflocation tag >>
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 This article is excerpted from chapter three of the book ColdFusion Web Development with Dreamweaver MX 2004, written by Jen and Peter deHaan et al. (Apress; ISBN: 1590592379). Check it out today at your favorite bookstore. Buy this book now.
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