ColdFusion Loops (cfloop)

A ColdFusion loop is a block of code that executes continuously either a secified number of times, once for each element in an object, or while a condition is true.

In ColdFusion, you use the cfloop tag to perform a loop. The cfloop tag has a number of different attributes. The attributes used depends on the type of loop you're performing.

Syntax

<cfloop attribute1="" attribute2="">
  Do something for each iteration of the loop.
</cfloop>

The Index Loop

An index loop is a loop that continues for a specified number of times.

You use the from and to attributes to specify how many iterations should occur. The index attribute holds the counter - it starts with the value of the to attribute and is incremented for each iteration of the loop (until it reaches the value of the from attribute).

ColdFusion code:

<cfloop from="1" to="5" index="i">
  <cfoutput>
  #i#<br />
  </cfoutput>
</cfloop>

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The (optional) step attribute allows you to determine how big the increments will be.

ColdFusion code:

<cfloop from="1" to="10" index="i" step="2">
  <cfoutput>
  #i#<br />
  </cfoutput>
</cfloop>

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The Conditional Loop

A conditional loop is a loop that executes while a condition is true.

You use the condition attribute to specify the condtion to use.

The following example uses a variable to determine whether to reiterate the loop or not. If the value of the variable is equal to false, the loop will continue to iterate. If it is set to true, it will exit the loop and continue the rest of the code.

In this example, we use ColdFusion's RandRange() function to pick a random number between 1 and 10. If the number is 10, the myVar variable is set to true.

ColdFusion code:

<cfset myVar=false>
<cfloop condition="myVar eq false">
  <cfoutput>
  myVar = <b>#myVar#</b>  (still in loop)<br />
 </cfoutput>
  <cfif RandRange(1,10) eq 10>
    <cfset myVar="true">
  </cfif>
</cfloop>
<cfoutput>
myVar = <b>#myVar#</b> (loop has finished)
</cfoutput>

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Tip: Refresh this page a few times and you should see the number of lines change (due to a different random number being generated within the loop).

The Query Loop

You can loop over the results of a ColdFusion query (i.e. using the cfquery tag). Don't worry - if you don't know what I mean by that, we will be learning about ColdFusion queries soon.

ColdFusion code:

<cfquery name="getMovies" datasource="Entertainment">
  select top 4 movieName
  from Movies
</cfquery>
<cfloop query="getMovies">
   #movieName#
</cfloop>

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The List Loop

You can loop over a list.

You can use the (optional) "delimter" attribute to specify which characters are used as separators in the list.

<cfloop list="ColdFusion,HTML;XML" index="ListItem" delimiters=",;">
  <cfoutput>
   #ListItem#<br />
 </cfoutput>
</cfloop>

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The File Loop

You can loop over a file. To do this, you use the same attributes as you would for a list.

<cfloop list="#myFile#" index="FileItem" delimiters="#chr(10)##chr(13)#">
  <cfoutput>
   #FileItem#<br />
 </cfoutput>
</cfloop>

COM Collection/Structure Loops

You can loop over a Structure or COM collection.

<cfset myBooks = StructNew()>
<cfset myVariable = StructInsert(myBooks,"ColdFusion","ColdFusion MX Bible")>
<cfset myVariable = StructInsert(myBooks,"HTML","HTML Visual QuickStart")>
<cfset myVariable = StructInsert(myBooks,"XML","Inside XML")>
<cfloop collection="#myBooks#" item="subject">
  <cfoutput>
 <b>#subject#:</b> #StructFind(myBooks,subject)#<br />
 </cfoutput>
</cfloop>

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