LmÉPï C Á npï À ƵÀ ïì itech Analytic Solutions

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1 LmÉPï C Á npï À ƵÀ ïì itech Analytic Solutions No. 9, 1st Floor, 8th Main, 9th Cross, SBM Colony, Brindavan Nagar, Mathikere, Bangalore itechanalytcisolutions@gmail.com Website: Mobile:

2 Chapter 4 Understanding VBA No. 9, 1 st Floor, 8 th Main, 9 th Cross, SBM Colony, Brindavan Nagar, Mathikere, Bangalore Page: 2

3 VBA Terminology Before you plunge into my VBA coverage, here's a review of some basic VBA terminology: Keyword: A word that has special meaning in VBA. For example, in the English language, the word now simply indicates a point in time. In VBA, Now is the name of a built-in VBA function that returns the current date and time. Statement: A single VBA word or combination of words that constitutes an instruction to be performed by the VBA engine. Procedure: A collection of VBA statements that are grouped together to perform a certain task. You might, for example, write a complex procedure that extracts data from a table, combines the data in a particular way, and then displays the data on a form. Or, you might write three smaller procedures, each of which performs a single step of the overall process. There are two types of VBA procedures: subs (subroutines) and functions: o Subroutines perform a single task and then just go away. o Functions perform a task and then return a value, such as the result of a calculation. The example described earlier, where the procedure extracts data from a table, is actually a subroutine. It performs a specific task; then, when it ends, the procedure just goes away. The example where the operation is split into three smaller procedures includes a function. In this case, the first procedure that opens the database and extracts data most likely returns the data as a recordset, and the recordset is passed to the other procedures that perform the data combination and data display. Module: Procedures live in modules. If statements are like sentences and procedures are like paragraphs, modules are the chapters or documents of the VBA language. A module consists of one or more procedures and other elements combined as a single entity within the application. Variable: Variables are sometimes tricky to understand. Because Access is a database development tool, it makes sense that VBA code has to have some way of managing the data involved in the application. A variable is nothing more than a name applied to represent a data value. In virtually all VBA programs, you create and use variables to hold values such as customer names, dates, and numeric values manipulated by the VBA code Understanding Objects Visual Basic is an (OO) object-oriented language. Performing a task in Visual Basic (VB) or Visual Basic for Applications (VBA) involves manipulating various types of objects, each of which may have several different properties and methods. To perform a task using VBA you return an object that represents the appropriate Excel element and then manipulate it using the objects methods and properties. Objects A simple statement Range( A1 ).Select illustrates an important characteristic of VB. The syntax of many statements first specifies an object, Range( A1 ), and an action upon it, Select. An object is a special type of variable that contains both data and code and represents an element of Excel. Objects exist only in the computer s memory; they don t appear in your code. There are many types of objects in VB, and even more in Excel VBA. Excel objects that you will encounter include the Application object which No. 9, 1 st Floor, 8 th Main, 9 th Cross, SBM Colony, Brindavan Nagar, Mathikere, Bangalore Page: 3

4 represents the Excel application itself, the Worksheet object representing a worksheet, and the Range object representing an individual cell or a rectangular range of cells (e.g. cells A2:C9 of the currently active worksheet). Objects have types just as variables have data types.. Object types are called classes. Workbook, Worksheet and Range are just a few of Excel s object classes. For Excel spreadsheets, functions etc. to be controlled and manipulated from a VBA program, these things in Excel must have corresponding objects that can be referred to in the program. The collection of objects corresponding to things in the Excel application is called the Excel object model. Methods In VB an action that an object can perform is referred to as a method. Thus a method of an object is a procedure that carries out some action involving the object. Consider the object Dog. To cause it to bark we could write Dog.Bark. However a Dog is capable of more than barking, for example we could have Dog.Sit, Dog.Fetch. In Excel, for example, the statement ActiveCell.Delete calls the Delete method of the ActiveCell object, which deletes the contents of the cell. Like any other procedure, a method of an object can take one or more arguments, as in this example: ActiveCell.AddComment This is a comment The list of methods that an object can perform depends on the object. For example, the Range object supports about 80 different methods. A method is accessed by following the relevant object with a dot and then the name of the method. Properties An object can have properties. A property is a quality or characteristic of the object, e.g. the length of the dog s tail, the loudness of its bark. If you think of objects as the nouns of VB, then properties are its adjectives and methods are its verbs. In Excel the properties may themselves be either primitive data types such as numbers, strings or Boolean values, or may themselves be objects of some kind. One of the many properties of the Application object is called Name, and is a read only string containing the name of the application, i.e. Microsoft Excel. It can be accessed by adding a dot and the Name property after the object: MsgBox Application.Name The Application object also has a property called ActiveCell, which represents the currently active cell in the active Excel worksheet. ActiveCell is an instance of the object type called Range, and one of its properties is called Value and represents the value (number, string or formula) held by the cell. No. 9, 1 st Floor, 8 th Main, 9 th Cross, SBM Colony, Brindavan Nagar, Mathikere, Bangalore Page: 4

5 The statement Application.ActiveCell.Value = Hello will place the string Hello in the active cell. Many properties of the Application object can be used without using the qualifier Application in this example - and the above statement could simply be written ActiveCell.Value = Hello Let s consider in detail the statement Worksheets( sheet1 ).Range( A1 ).Value = 3 Step 1 - Worksheets( sheet1 ) evaluates the worksheets method and returns the object that refers to sheet1. So we now have [Worksheet object that refers to sheet1].range( A1 ).Value = 3 Step 2 evaluates the Range method to return the object that refers to cell A1 of sheet1. So we now have [Range object that refers to cell A1 of sheet1].value = 3. Step 3 evaluates the Value property of the range object at sets it to the number 3. Using the Immediate Window Most useful for executing VBA statements directly, testing statements and helping to debug your code The two main functions are to and to Send output to be viewed during execution Execute commands immediately. Let s you run any VBA statement, manually while a program is running. This is extremely powerful as it allows you to test and execute small parts of code Has the shortcut key (Ctrl + G) (View > Immediate Window) When a command is typed and Enter is pressed - the command is executed immediately. To execute the command again click anywhere in the line and press Enter again. It is even possible to change the contents of variables at run-time. To evaluate an expression in the Immediate Window, precede your expression with a question mark (?). This is a short-cut for Print. There are two ways to print to the immediate window, either by including Debug.Print statements in the actual code or by entering print statements directly. Debug.Print Range("A1").Value? Range("A1").Value No. 9, 1 st Floor, 8 th Main, 9 th Cross, SBM Colony, Brindavan Nagar, Mathikere, Bangalore Page: 5

6 The immediate window contains the last 200 outputs implemented by Debug.Print The immediate window is particularlay useful for testing variables or properties Floating point numbers are generally displayed in the immediate window to at most eight places beyond the decimal point even when sixteen places exist. In the immediate window it is also possible to assign values to variables or properties or to start macros by giving their name. In the immediate window you can introduce new variables without any previous declaration (even when Option Explicit is declared) Allows you to: Type or paste a line of code and press ENTER to run it. Copy and paste the code from the Immediate window into the Code window but does not allow you to save code in the Immediate window. The Immediate window can be dragged and positioned anywhere on your screen unless you have made it a dockable window from the Docking Tab of the Options dialog box. You can close the window by clicking the Close box. If the Close box is not visible, double-click the Title bar to make the Close box visible, then click it. Note In break mode, a statement in the Immediate window is executed in the context or scope that is displayed in the Procedure box. For example, if you type Print variablename, your output is the value of a local variable. This is the same as if the Print method had occurred in the procedure you were executing when the program halted. Step 2 - Displaying Messages use the immediate window to test a statement? Application.Caption This window can perform two main tasks: 1. Displaying messages from your code using Debug.Print 2. Execute commands or procedutes directly. Debug.Print [(condition)] This statement allows you to enter break mode based on a condition. If the condition returns False or zero, then break mode is entered on that line. This is a very useful way to pause code execution when the unexpected happens. This is very similar to the statements found in C++. Always remember to remove all these statements before your code is distributed. No. 9, 1 st Floor, 8 th Main, 9 th Cross, SBM Colony, Brindavan Nagar, Mathikere, Bangalore Page: 6

7 Step 3 - Executing Commands Step 4 - Things to Remember You can execute lines of code directly into the Immediate window. You can execute multiple lines of code (including loops). You can include vbcrlf to make long text strings more readable No. 9, 1 st Floor, 8 th Main, 9 th Cross, SBM Colony, Brindavan Nagar, Mathikere, Bangalore Page: 7