1. Using Objects and Properties
Chapter 5
Using Objects and Properties

2. Chapter Objectives
Define and explain the roles of objects and properties in an Access database
Describe the difference between Microsoft Access objects, Data Access Objects (DAO), and ActiveX Data Objects (ADO)
Write dot and bang notation that retrieves and updates object properties in a macro and module
Create a query with a criterion that references a control on a form

3. Chapter Objectives
Modify the properties of a form through a macro or VBA statement
Modify the properties of a linked table
Create recordsets in a VBA procedure
Find and describe properties related to many objects, including forms, reports, tables, commands, controls, fields, databases, and recordsets

4. The World According to Objects
Each object has properties
Data items that describe the objects
Object characteristics:
Can contain other objects
Have methods
Capabilities or procedures that the object can perform
Related objects can be grouped

5. The World According to Objects
A group of objects, called a subclass, is a subset of another group of objects, called a superclass
Class inheritance
Process when a new subclass is placed inside a superclass, objects within that subclass inherit the properties of the superclass

6. The World According to Objects
Object-oriented development environment
Uses objects that have the features just described
Object-based development environment
Supports object properties, object methods, collections, and objects that contain other objects

7. Objects and Collections in Access
Three major categories of objects exist:
Microsoft Access objects
Created and maintained by Access programming environment
Primarily relate to the user interface and modules
DAO objects
Created and managed by the Jet database engine
Primarily involve objects related to data storage and retrieval
TableDef and QueryDef objects are examples of DAO objects

8. Objects and Collections in Access
Three major categories of objects exist (continued):
ADO objects
Similar to DAO objects
Table object replaces the TableDef object used in DAO and the Command object replaces the QueryDef DAO object

9. Objects and Collections in Access
An object that contains related objects
Tables collection
Contains definitions of all Table objects
Forms collection
Contains all open forms; all forms that are loaded

10. Objects and Collections in Access
Each TableDef object owns a Fields collection that in turn contains the Fields objects in the table
Each Form object owns a Controls collection that contains all of the controls in the form
Count property of a collection
Indicates the number of objects in the collection

11. Objects and Collections in Access
Figure 5-1 Some of the relationships among Microsoft Access objects

12. Objects and Collections in Access
Figure 5-2 Relationships among DAO objects

13. Objects and Collections in Access
Figure 5-3 Relationships among ADO objects

14. Objects and Properties in Access
Dot notation
Syntax used by VBA, macros, and queries
Uses the dot (.) operator to indicate that what follows is an item defined by Microsoft Access
Bang notation
Notation using the exclamation point (!)
Can be used in place of dot notation when the collection referenced by an object is the default collection

15. Objects and Collections in Access
Keywords can be used to shorten object property paths
VBA can use the word Me inside a form or report class module to refer to the form or report that contains the module
A form or report class module can use the word Parent to refer to a form or report that contains another form or report

16. Changing Property Values
VBA can change the value of a property by using the assignment statement in a VBA procedure
VBA supports several data types:
Integer is a relatively small integer
Long is a larger integer
Single is a real number

17. Changing Property Values
VBA supports several data types (cont.):
Double is a real number that offers twice as much storage space and precision as a Single
String is a series of characters or numbers
Boolean is True or False
Variant can contain anything

18. Changing Property Values
Table 5-1 Microsoft Access objects

19. Changing Property Values
The SetValue action requires two action arguments:
Item argument
Contains the dot or bang notation that identifies the property
Expression argument
Contains the new value

20. Changing Property Values
Figure 5-5 Macro action that shows a form’s Form Header

21. The Application Object and Properties
Represents the Access application that is currently running
MenuBar
Identified the default menu that will be displayed when the application opens
Intrinsic constant
Name used by Access to represent a particular integer

22. The Application Object and Properties
Table 5-2 Some Application object properties

23. The Screen Object and Properties
Refers to the form, report, or control that is currently active on the screen
Some screen properties are read-only
Macros and VBA statements can read the current value but cannot change it

24. The Screen Object and Properties
Table 5-3 Important Screen properties

25. Objects and Properties Related to Forms, Reports, and Controls
Table 5-4 Commonly used properties associated with format or appearance

26. Objects and Properties Related to Forms, Reports, and Controls
Table 5-5 Commonly used properties associated with updating data

27. Objects and Properties Related to Forms, Reports, and Controls
Table 5-5 Commonly used properties associated with updating data (continued)

28. Objects and Properties Related to Forms, Reports, and Controls
Caption property
Displays text in the title bar of the form
AllowAdditions
A False setting prohibits the entry of new records
Filter property
When the FilterOn property equals True, the Filter property restricts the rows that the form displays to those rows that meet the criteria

29. Manipulating Record Sources and Row Sources
Specifies a table or query that contains the values listed in combo or list box
Record source
Identifies table or query that supplies data to the entire form, page, or report
Changing the value of a record source or row source in a module or macro changes the data displayed by the form, page, report, combo box, or list box

30. Nuances of Forms, Reports, and Controls Notation
When the Modal property of a form is True, a user cannot perform an operation on any other form until the current, or modal, form is closed
When the PopUp property of a form property is True, Access places the current form in front of all other open forms

31. Nuances of Forms, Reports, and Controls Notation
Figure 5-6 Creating a hierarchical sequence of combo boxes

32. Data Access Objects and Their Properties
Table 5-6 Commonly used DAO objects

33. Data Access Objects and Their Properties
Table 5-6 Commonly used DAO objects (continued)

34. DBEngine, Workspace, and the Database Objects
Represents an open database and is managed within the context of a Workspace
Workspace object
Defines how an application interacts with data
Database engine (DBEngine object)
Manages workspaces
Compromises the built-in procedures that retrieve and update data in response to a user’s request

35. ActiveX Data Objects and Properties
ActiveX Data Objects model (ADO)
Not hierarchical like the DAO model
Figure 5-7 ActiveX Data Objects Database Data Model (ADODB)

36. ActiveX Data Objects and Properties
Figure 5-8 ActiveX Data Objects Extensions for DDL and Security Data Model (ADOX)

37. ActiveX Data Objects and Properties
Figure 5-9 ActiveX Data Objects Jet Replication Objects Data Model (JRO)

38. Libraries
The libraries needed to support ADOX and JRO are not automatically loaded by Access
If using both DAO and ADO objects in an Access project:
Specify which library to use when declaring objects
DAO and ADO include several objects with the same names

39. Connection Object Connection object
Establishes a connection to the database and defines a session in which a user interacts with the data
Table 5-7 Commonly used ADODB Connection object properties

40. Connection Object
Table 5-7 Commonly used ADODB Connection object properties (continued)

41. Catalog and Table Objects
Catalog object
Represents a database
Table object
Contains the definitions that define the table structures in the database
Used to access properties of the table’s design

42. Catalog and Table Objects
Table 5-8 Commonly used Table object properties

43. Catalog and Table Objects
Some properties are optional
Managed by the database engine only when they are created in VBA code or set by the system developer through Design or Datasheet view of an object
Description property
Created by Microsoft Access (not the database engine) through the Table property sheet

44. Field Objects and Properties
Every Table object owns a Columns collection
As you append columns to the Columns collection
Specify the information needed for the Data Type

45. Index Objects and Properties
Indexes are fields used to find and sort records in a table
Keys are either primary keys or foreign keys
Table 5-9 Commonly used ADOX Index properties

46. Table 5-10 Commonly used ADODB Command properties
Command Object
Command Object
Can contain information needed to define a query
Table Commonly used ADODB Command properties

47. Recordset Objects and Properties
Provide access to the actual data stored in and retrieved from the database
ADO recognizes four general types of recordsets, which are determined by the CursorType property setting
Dynamic cursors
Fully scrollable

48. Recordset Objects and Properties
Four general types of recordsets (cont.):
KeySet cursors
Fully scrollable, but do not offer the capability of seeing changes made by other users
Forward Only cursors
Not scrollable
Static cursors
Fully scrollable, yet do not offer the option of seeing changes made by anyone in a Static cursor

49. Recordset Objects and Properties
Table Allowed CursorType/LockType combinations in ADO

50. Recordset Objects and Properties
Figure Prospect processing module section

51. Recordset Objects and Properties
Procedure-level (or local variable)
A variable used only in the current procedure
Table Commonly used Recordset properties

52. Recordset Objects and Properties
Bookmark property of a recordset
Points to the current record
EOF property
Equals True when a previously executed Find method does not find a record that matches a specified criterion
Equals True when the bookmark advances past the last record in the recordset

53. Objects Defined by Other Applications
An Access application can use objects managed by other applications
To write code that uses objects from another application:
Microsoft Access References collection must contain an object that identifies the other application

54. Chapter Summary Access is an object-based database environment
Tables, queries, forms, reports, and even database are objects
Other objects that support data access activities are recordsets and workspaces

55. Chapter Summary
Access maintains hundreds of data items, called properties, that describe the objects in an Access database
Objects are grouped into collections
Collections are associated with the user interface or with the database engine

56. Chapter Summary
Generally, properties can be examined and changed by opening the property sheet associated with the object
Most properties can be manipulated through VBA
Macros and VBA allow programmers to change object properties while the program is running