Unfortunately, I did not win in the ColdFusion weekly podcast (congratulations Dan Vega), but I think I had a cool answer that ya'll might be interested in seeing. Here is their question (as taken from the ColdFusion weekly website):
Programming exercise! In CF (obviously) write a script that loops from 1 to 100 and outputs the numbers. When a number is a multiple of 3, output "ColdFusion" and a line break. When a number is a multiple of 5, output "Rocks" and a line break. When a number is a multiple of 3 and 5, output "ColdFusion Rocks" and a line break. Slickest solution wins!
I took a two pronged approach to this answer. The first is a simple index loop using CFLoop (just to satisfy the question). The second approach is a sweet-ass ColdFusion custom tag that actually utilizes the CFExit method="LOOP" attribute (heck yeah!).
Ok, so here's the simple answer:
<!--- Loop from 1 to 100. ---> <cfloop index="intI" from="1" to="100" step="1"> <!--- Output the line number. ---> #intI#. <!--- Check to see if this is a multiple of 3. ---> <cfif NOT (intI MOD 3)> ColdFusion </cfif> <!--- Check to see if this is a multilple of 5. ---> <cfif NOT (intI MOD 5)> Rocks! </cfif> <!--- ASSERT: The above to CFIF statements will handle cases were the number is BOTH a multiple of 3 and of 5. No need to handle those seperately (ie. MOD 15 is already being handled). ---> <br /> </cfloop>
Ok, that's pretty basic. But, it's not that flexible. I then created a ColdFusion custom tag to make this more open ended and seriously upped the "cool" factor. Before we get into how it's done, let's look at how it is called:
!--- This can be run as a self-closing tag. ---> <cfmodule template="cfweeklyloop.cfm" from="1" to="100" step="1" mod3="ColdFusion" mod5="Rocks!" /> <!--- Or it can be run as a tag that allows custom output inbetween each line item. ---> <cfmodule template="cfweeklyloop.cfm" from="1" to="100" step="1" mod3="ColdFusion" mod5="Rocks!"> <hr /> </cfmodule>
As you can see above, the custom tag (executed via CFModule) uses the attributes "mod3" and "mod5" to accomplish what was accomplished in the first CFLoop tag. Ok, so now, let's look at the code:
<!--- Kill extra output. ---> <cfsilent> <!--- Check to see which version of the tag we are executing. We only care about validating the tag attributes on the start tag, not on the end tag. ---> <cfswitch expression="#THISTAG.ExecutionMode#"> <cfcase value="START"> <!--- Param tag attributes. ---> <cfparam name="ATTRIBUTES.From" type="numeric" /> <cfparam name="ATTRIBUTES.To" type="numeric" /> <cfparam name="ATTRIBUTES.Step" type="numeric" default="1" /> <!--- Validate the step value to make sure an infinite loop will never take place. ---> <cfif (ATTRIBUTES.Step EQ 0)> <!--- This tag loop will never end. ---> <cfthrow type="EXCEPTION" message="Invalid Loop Parameters" detail="The FROM value #ATTRIBUTES.From#, TO value #ATTRIBUTES.To#, and STEP value #ATTRIBUTES.Step# will result in an infinite loop." /> </cfif> <!--- Create a struct of mod value to check. ---> <cfset THISTAG.ModValues = StructNew() /> <!--- Loop over the tag attributes to find the mod values. Remember, at the time of the tag execution, we are not sure yet which MOD attribute are actually being passed in. We have to find them manually. ---> <cfloop item="strKey" collection="#ATTRIBUTES#"> <!--- Check to see if this key matches the MOD patterns. ---> <cfif strKey.Matches( JavaCast( "string", "(?i)MOD[\d]+" ) )> <!--- This is a MOD value. We have to store both the mod value and the resultant output value into the struct. ---> <cfset THISTAG.ModValues[ strKey.ReplaceFirst( "(?i)^MOD", "" ) ] = ATTRIBUTES[ strKey ] /> </cfif> </cfloop> <!--- Now that we have a structure that contains keys and output values, we have to get the array of keys. We want this key to be in smallest-value first as these will be most likely to be output. ---> <cfset THISTAG.ModKeys = StructKeyArray( THISTAG.ModValues ) /> <!--- Sort the keys. ---> <cfset ArraySort( THISTAG.ModKeys, "numeric", "ASC" ) /> <!--- Initialize the tag to have the index equal to the FROM attribute. This is the index that will keep track of our loop from iteration to iteration. ---> <cfset THISTAG.Index = ATTRIBUTES.From /> </cfcase> <cfcase value="END"> <!--- If this is the first iteration, check to see if we should even execute it. ---> <cfif ( (THISTAG.Index EQ ATTRIBUTES.From) AND ( ( (ATTRIBUTES.Step GT 0) AND (THISTAG.Index GT ATTRIBUTES.To) ) OR ( (ATTRIBUTES.Step LT 0) AND (THISTAG.Index LT ATTRIBUTES.To) ) ) )> <!--- This tag is starting out of bounds. Exit out of the tag. Try to kill any generated output. ---> <cfset THISTAG.GeneratedContent = "" /> <!--- Exit tag. ---> <cfexit method="EXITTAG" /> </cfif> </cfcase> </cfswitch> <!--- ASSERT: If we have reached this point then we are either in the START mode of the tag or we have reached the END mode of the tag and we are definitely going to execute the tag at least once (for the given iteration). ---> </cfsilent> <!--- We only want the output stuff to happen in the end tag. ---> <cfif (THISTAG.ExecutionMode EQ "End")> <cfoutput> <!--- Output the index. ---> #THISTAG.Index#. <!--- Loop over the possible MOD values that we collected earlier in the tag. ---> <cfloop index="intMod" from="1" to="#ArrayLen( THISTAG.ModKeys )#" step="1"> <!--- Check to see if this key MODs evenly into the current iteration index. ---> <cfif NOT (THISTAG.Index MOD THISTAG.ModKeys[ intMod ])> <!--- We have a match. Output the value stored at this mod key. ---> #THISTAG.ModValues[ THISTAG.ModKeys[ intMod ] ]# </cfif> </cfloop> <!--- Line break. ---> <br /> </cfoutput> <!--- Kill extra output. ---> <cfsilent> <!--- Increment the tag index. ---> <cfset THISTAG.Index = (THISTAG.Index + ATTRIBUTES.Step) /> <!--- Check to see which direction we are going in in the loop and if we can increment. If we can, then loop to the beginning of the tag. ---> <cfif ( ( (ATTRIBUTES.Step GT 0) AND (THISTAG.Index LTE ATTRIBUTES.To) ) OR ( (ATTRIBUTES.Step LT 0) AND (THISTAG.Index GTE ATTRIBUTES.To) ) )> <!--- We still have more interations to perform. This will break out of the current tag execution an re-execute the tag keeping the same tag variables in place. ---> <cfexit method="LOOP" /> <cfelse> <!--- We must end the loop. ---> <cfexit method="EXITTAG" /> </cfif> </cfsilent> </cfif>
So there you go. It was a lot of fun to write this and I was totally excited to finally get to use the LOOP directive for the CFExit tag - it's not often that that is useful. Plus, you can add any MODX attributes to the tag you want (where X is some integer).
I have been a long time listener to the ColdFusion weekly podcast and now, I am finally a participant. I may have lost this battle, but the next one is mine!
Want to use code from this post? Check out the license.