Microsoft Access Illustrated

Microsoft Access 2013 - Illustrated
Unit N: Creating Modules and VBA

Objectives Understand modules and VBA Compare macros and modules
Create functions Use If statements Microsoft Office Illustrated

Objectives (cont’d.) Document procedures Build class modules
Modify sub procedures Troubleshoot modules Microsoft Office Illustrated

Understand Modules and VBA
Module: an Access object that stores Visual Basic for Applications (VBA) programming code Visual Basic Editor (VBE): program for writing VBA code Microsoft Office Illustrated

Understand Modules and VBA (cont’d.)
Two kinds of modules in an Access database Standard modules: contain global code executable from anywhere in the database Displayed as module objects in the Navigation Pane Class modules: code stored within the form or report object itself; can only be executed in that object Microsoft Office Illustrated

Module: contains VBA programming code organized in procedures Procedure: contains several lines of code; each line is a statement. Comments: text that helps explain and document the code Microsoft Office Illustrated

Procedure: a series of VBA statements Performs an operation or calculates an answer Two types of procedures: Functions Subs (sub procedure) Microsoft Office Illustrated

Function: a procedure that returns a value Sub: performs a series of VBA statements to manipulate controls and objects Arguments: constants, variables, or expressions Passed to a procedure; required in order for the procedure to execute Microsoft Office Illustrated

Object: any item that can be identified or manipulated Includes: traditional Access objects (table, query, form, etc.) as well as other items (e.g., controls, sections, and existing procedures) that have properties Method: an action that an object can perform Microsoft Office Illustrated

VBE window for a standard module Microsoft Office Illustrated

Components and text colors for the Visual Basic Editor window Microsoft Office Illustrated

Components and text colors for the Visual Basic Editor window (cont’d.) Microsoft Office Illustrated

Compare Macros and Modules
Macros: easy way to handle common, repetitive, and simple tasks Examples: open and close forms, show and hide toolbars, and print reports Macros: generally easier to create than modules Macro Design View is more structured than the VBE Microsoft Office Illustrated

Compare Macros and Modules (cont’d.)
Creating a module: requires VBA programming language knowledge Must apply correct syntax (rules) for each VBA statement Macros: simpler to create VBA: more powerful Macro: must be used to make global, shortcut key assignments Microsoft Office Illustrated

AutoExec: special macro name Automatically executes when the database first opens Use a module to: Create a unique function Detect Access error and display custom message Apply more powerful If-Then logic Microsoft Office Illustrated

Use a module to (cont’d.): Declare variables Work in conjunction with SQL (Structured Query Language) to select, update, append, and delete data Microsoft Office Illustrated

Visual Basic Editor window for a class module Microsoft Office Illustrated

Common VBA keywords Microsoft Office Illustrated

Common VBA keywords (cont’d.)
Microsoft Office Illustrated

Create Functions Access supplies hundreds of functions such as: Sum, Count, IIf, First, Last, Date, and Hour Create a custom function in a module Can be used in any query, form, or report throughout the database Microsoft Office Illustrated

Create Functions (cont’d.)
End Function statement Automatically added by VBA Required statement marking the end of a function Microsoft Office Illustrated

Common VBA programming practice: apply three-character prefixes to name objects and controls Prefix bas: short for Basic; applies to global modules Microsoft Office Illustrated

Three-Character Prefix Naming Conventions

Use If Statements If...Then...Else logic: tests logical conditions and executes statements only if the conditions are true Microsoft Office Illustrated

Document Procedures Comment lines: statements in the code that document the code; do not affect how the code runs Start with an apostrophe and are green in the VBE Microsoft Office Illustrated

Document Procedures (cont’d.)
Adding comments to a module Microsoft Office Illustrated

Document Procedures (cont’d.)
Standard toolbar buttons in the Visual Basic window Microsoft Office Illustrated

Build Class Modules Class modules: contained and executed within specific forms and reports Most commonly run in response to an event (a specific action that occurs as the result of a user action) Microsoft Office Illustrated

Build Class Modules (cont’d.)
Creating an event handler procedure Microsoft Office Illustrated

Copying the If structure to a new event-handler procedure Microsoft Office Illustrated

Branch of Service combo box is visible when the Veteran check box is checked Microsoft Office Illustrated

Modify Sub Procedures Sub procedures: can be triggered on any event identified in the Property Sheet Examples: On Got Focus (when control gets the focus), After Update (after a field is updated), or On Dbl Click (when control is double-clicked) Item’s set of event properties: depends on the type of item Microsoft Office Illustrated

Modify Sub Procedures (cont’d.)
IntelliSense technology prompts you as you write VBA statements Microsoft Office Illustrated

Troubleshoot Modules Several techniques in Access for debugging different types of VBA errors Types of errors Syntax error: cannot be read by the Visual Basic Editor Occurs immediately as VBA statement is written Microsoft Office Illustrated

Troubleshoot Modules (cont’d.)
Types of errors (cont’d.) Compile-time errors: incorrectly constructed code Detected as soon as code is run or when Compile option selected on the Debug menu Run-time errors: incorrectly constructed code; stops code execution Examples: attempting an illegal operation e.g., dividing by zero Microsoft Office Illustrated

Types of errors (cont’d.) Logic errors: code runs without obvious problems; procedure does not produce the desired result Most difficult errors to troubleshoot Microsoft Office Illustrated

Setting a breakpoint Microsoft Office Illustrated

Stopping execution at a breakpoint Microsoft Office Illustrated

Microsoft Access Illustrated

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