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Chapter 9: Working with Arrays and Collections
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variable also has a name. VBA helps you create user-defined types of any
complexity. They can include arrays, other user-defined types, and even
objects. However, you always want to make the user-defined type as simple
as possible and document it fully so that you remember later what it does.
Knowing when to create 
your own data type
Before you create a user-defined data type, always ask whether any existing
type (including objects and collections) can fulfill your need. After you know
that you have to create a user-defined type, make sure that you think about
the purpose that the user-defined type fulfills.
A user-defined data type can save time and effort by letting you declare all
the data elements that you normally use together for a task in one place. It
can also group data so that you don’t have to perform finger gymnastics to
locate your data. However, the main reason to create a user-defined type is to
make your program easier to understand. A well-defined data type can make
your code simpler and keep the number of code lines to a minimum.
Accessing and manipulating data
The example in the earlier “Adding keyed data to the collection” section
works well because it doesn’t have to work with complex data. A program
that modifies multiple tables and 20 or 30 fields might not work so well by
using the technique shown in that section. (It would work, but it wouldn’t be
fun to program.) By using the new data type that you just created, you can
make the programming example in the “Adding keyed data to the collection”
section easier to understand.
The example in this section relies on a user-defined data type. It builds an
object on that data type and then adds the object to a collection. This exam-
ple shows how to create your own collections to make working with your
data faster and easier.
Defining an individual contact
When you decide to create your own collection, begin with the individual
object. Make sure that you know what one copy of an object looks like before
you create multiple copies of it. See Chapter 8 for a complete object creation
demonstration.
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