As promised, here is part 2 to my introduction to complex objects. This post will focus on arrays and query objects. Arrays Important Links: Adobe Livedocs - Array Functions Adobe Livedocs - About Arrays Arrays can be a more difficult concept to grasp than structures or lists. They are a more complex 'container' than structs or lists, but as such they can be more powerful. Unlike structures, the index of an array is always numeric. Arrays can have multiple 'dimensions' which can lead to some confusion early on when trying to comprehend these objects. I'll borrow some text from the Livedocs which gives a good intro to Arrays:

The following terms will help you understand subsequent discussions of ColdFusion arrays: * Array dimension The relative complexity of the array structure. * Index The position of an element in a dimension, ordinarily surrounded by square brackets: my1Darray[1], my2Darray[1][1], my3Darray[1][1][1]. * Array element Data stored at an array index. The simplest array is a one-dimensional array, similar to a row in a table. A one-dimensional array has a name (the variable name) and a numerical index. The index number references a single entry, or cell, in the array, as the following figure shows:

To understand arrays, it is easier to look at some sample code. Here is a simple one dimensional array: The visual representation that a dump gives us will help in understanding the concept of this 'container':

As stated above, arrays will sometimes be multi-dimensional. Though this can seem intimidating, it really isn't that bad. A 2d array is nothing more than a 1d array that contains another 1d array within each element. Which looks like this -

A 3d Array just builds on the previous concepts. Which looks like this -

This is a very simple overview of Arrays, but breaking it down to this level will hopefully give you a good understanding of the concepts surrounding the array 'container'. The more you work with them, the more comfortable you will become. Soon you will be iterating over an array dynamically to access the elements within them. Again, like the other 'containers', it's a good idea to read the documentation and become comfortable with the functions that are used to work with them. You will often see arrays containing structures (an arrayOfStructs), which really is not a difficult concept if you build on these concepts. A quick example:

To access the struct within each element: Queries Important Links: Adobe Livedocs - Query Functions I'm not sure if the query object fits the official definition of a 'complex object', however it is certainly a 'container' and should be understood as one. When I first started working with CF, for some reason I could not grasp the concept of a query being anything other than what was returned when you used the tag. However, many of the tags in CF return a query object (cfpop, cfdirectory just to name a few) and query objects can be created totally independent of the tag. It may help to think of the query object as a 'record set,' or a 'container' that looks exactly how you would expect data to look as it would in your database. That is, a single row of column headers followed by rows of data aligning with those headers. The query functions can be used to manipulate the query object (like adding a row or a column). Here's a quick example of creating a query object using query functions.

<!---
create a quick query object
--->
<cfset theQuery = QueryNew("userName, address, zipCode, phoneNumber")>
<!--- add a row --->
<cfset queryAddRow(theQuery, 1)>
<cfset querySetCell(theQuery, "userName", "bob smith", 1)>
<cfset querySetCell(theQuery, "address", "123 main st", 1)>
<cfset querySetCell(theQuery, "zipCode", "12345-1234", 1)>
<cfset querySetCell(theQuery, "phoneNumber", "123-456-7890", 1)>

<!--- if we had to break out the first section
of the zip code and create a new column for
some reason, here's how we'd do it --->

<!--- create a new one dimensional array for the new column --->
<cfset zipFirst = ArrayNew(1)>
<cfset queryAddColumn(theQuery, "zipWithoutLastFour", "integer", zipFirst)>

<cfloop from="1" to="#theQuery.recordCount#" index="i">
    <cfset theNewZip = listFirst(theQuery.zipCode, "-")>
    <cfset querySetCell(theQuery, "zipWithoutLastFour", theNewZip, i)>
</cfloop>

<cfdump var="#theQuery#">

That pretty much wraps up my overview of complex objects or as I like to call them 'containers.' I hope it has been helpful to someone out there. These are very critical building blocks. Many of the advanced techniques you may employ some day will no doubt demand an understanding of them. I was going to include an overview of XML objects in CF, but I think I'll hold off on that for now. Anyways, if you made it this far, thank you for reading! Other References ColdFusion Cookbook - Data Structures