MACROMEDIA COLDFUSION MX 61-DEVELOPING COLDFUSION MX, Develop Manual

Page: 104 / 860

104 Chapter 5: Using Arrays and Structures
About arrays
Traditionally, an array is a tabular structure used to hold data, much like a spreadsheet table with
clearly defined limits and dimensions.
In ColdFusion, you typically use arrays to temporarily store data. For example, if your site lets
users order goods online, you can store their shopping cart contents in an array. This lets you
make changes easily without committing the information, which the user can change before
completing the transaction, to a database.
Basic array concepts
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:
Thus, the following statement sets the value of the fifth entry in the one-dimensional array
MyArray to “Robert”:
<cfset MyArray[5] = "Robert">
A basic two-dimensional (2D) array is like a simple table. A three-dimensional (3D) array is like a
cube of data, and so on. ColdFusion lets you directly create arrays with up to three dimensions.
You can use multiple statements to create arrays with more than three dimensions.
The syntax
my2darray[1][3]="Paul"
is the same as saying 'My2dArray is a two-dimensional
array and the value of the array element index [1][3] is "Paul"'.
About ColdFusion arrays
ColdFusion arrays differ from traditional arrays, because they are dynamic. For example, in a
conventional array, array size is constant and symmetrical, whereas in a ColdFusion array, you can
have rows of differing lengths based on the data that has been added or removed.
The following figures show the differences between traditional arrays and ColdFusion arrays
using 2D arrays. The differences between traditional and ColdFusion 3D arrays are similar, but
much harder to show on a page.