Don't forget to use 'break' in switch/case statements
ColdFusionI was recently attempting to broaden my skillset a bit by reading a simple introductory book that is more or less the equivalent of "Java for Dummies". In a section that talked about conditional logic, it made the statement that you should always remember to add a "break;" at the end of each case within a switch statement or the remaining conditions would be processed in after the matching one.
I was thinking at the time that I knew this was not how ColdFusion processed code using cfscript/cfcase, but I realized that I wasn't entirely sure how this was handled in cfscript.
I decided to run a quick test and found that it behaves identically to Java. To set up a baseline for my test, I made a quick switch/case in tags like this:
As expected when I ran this, the string "second" appeared on the screen. In atempt to do the exact same thing in script, only excluding the "break" after each case, I ran this:
Sure enough, it behaved exactly as the Java book had described that Java would handle this as the screen displayed: "secondthird".
So, understanding this behavior, is there something useful that could be accomplished by purposefully omitting breaks?
See listing 10-16, and 10-17.
I'm currently building an app with a _very_ hierarchially driven data model. We have parent-child relationships between tables that go down about 10 or more levels (this is part of the business model, which is designed to mirror an industry standard so our code is compatible with other vendors).
In my case, I often need to delete "child data" at a certain level in my heirarchy. and the break-less "case" statements are perfect for this. Like so:
case "parent": delete_child();
case "child": delete_grandchild();
case "grand_child": delete_great_grandchild():
default: return false;
so if I pass in "parent", all of the "child records" below that will get deleted. But if I pass in "child", my "parent" stays valid, but eveyrthing below is still deleted, which is correct.
hth
Nolan
Anyhoo, JavaScript works the same way to cfscript which I often use in similar ways to Nolan's example. cfcase is a little different in that it can take in a list of values.
switch ( expression ) {
case 1:
case 2:
case 3:
/** do something if the value is 1, 2 or 3 */
break;
case 4:
/** do something if the value is 4 */
break;
}
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