Excel 2019 Power Programming with VBA. Michael Alexander

Чтение книги онлайн.

Читать онлайн книгу Excel 2019 Power Programming with VBA - Michael Alexander страница 31

Excel 2019 Power Programming with VBA - Michael Alexander

Скачать книгу

ActiveWindow The active window. ActiveWorkbook The active workbook. Selection The object selected. It could be a Range object, Shape, ChartObject, and so on. ThisWorkbook The workbook that contains the VBA procedure being executed. This object may or may not be the same as the ActiveWorkbook object.

      The advantage of using these properties to return an object is that you don't need to know which cell, worksheet, or workbook is active, and you don't need to provide a specific reference to it. This allows you to write VBA code that isn't specific to a particular workbook, sheet, or range. For example, the following instruction clears the contents of the active cell, even though the address of the active cell isn't known:

      ActiveCell.ClearContents

      The example that follows displays a message that tells you the name of the active sheet:

      MsgBox ActiveSheet.Name

      If you want to know the name and directory path of the active workbook, use a statement like this:

      MsgBox ActiveWorkbook.FullName

      If a range on a worksheet is selected, you can fill the entire range with a value by executing a single statement. In the following example, the Selection property of the Application object returns a Range object that corresponds to the selected cells. The instruction simply modifies the Value property of this Range object, and the result is a range filled with a single value.

      Selection.Value = 12

      If something other than a range is selected (such as a ChartObject or a Shape), the preceding statement generates an error because ChartObject and Shape objects don't have a Value property.

      The following statement, however, enters a value of 12 into the Range object that was selected before a non-Range object was selected. If you look up the RangeSelection property in the Help system, you find that this property applies only to a Window object.

      ActiveWindow.RangeSelection.Value = 12

      To find out how many cells are selected in the active window, access the Count property. Here's an example:

      MsgBox ActiveWindow.RangeSelection.Count

      Understanding methods

      Methods are the actions that can be performed with an object. It helps to think of methods as verbs. You can paint your house, so in VBA, that translates to something like house.paint.

      A simple example of an Excel method is the Select method of the Range object.

      Range("A1").Select

      Another is the Copy method of the Range object.

      Range("A1").Copy

      More about arguments

      An issue that often leads to confusion among new VBA programmers concerns arguments. Some methods use arguments to clarify further the action to be taken, and some properties use arguments to specify additionally the property value. In some cases, one or more of the arguments are optional.

      Consider the Protect method for a workbook object. Check the Help system, and you'll find that the Protect method takes three arguments: Password, Structure, and Windows. These arguments correspond to the options in the Protect Structure and Windows dialog box.

      If you want to protect a workbook named MyBook.xlsx, for example, you might use a statement like this:

       Workbooks("MyBook.xlsx").Protect "xyzzy", True, False

      In this case, the workbook is protected with a password (argument 1). Its structure is protected (argument 2) but not its windows (argument 3).

      If you don't want to assign a password, you can use a statement like this:

       Workbooks("MyBook.xlsx").Protect , True, False

      The first argument is omitted, and we specified the placeholder by using a comma.

      You can make your code more readable by using named arguments. Here's an example of how you use named arguments for the preceding example:

       Workbooks("MyBook.xlsx").Protect Structure:=True, Windows:=False

      Using named arguments is a good idea, especially for methods that have many optional arguments and also when you need to use only a few of them. When you use named arguments, you don't need to use a placeholder for missing arguments.

      For properties (and methods) that return a value, you must use parentheses around the arguments. For example, the Address property of a Range object takes five optional arguments. Because the Address property returns a value, the following statement isn't valid because the parentheses are omitted:

       MsgBox Range("A1").Address False ' invalid

      The proper syntax for such a statement requires parentheses as follows:

       MsgBox Range("A1").Address(False)

      You can also write the statement using a named argument:

       MsgBox Range("A1").Address(RowAbsolute:=False)

      These nuances will become clearer as you gain more experience with VBA.

      Much of the work that you will do in VBA involves cells and ranges in worksheets. That being the case, let's take some time to use the Range object as a case study on how to explore and get familiar with a specific object.

      Finding the properties of the Range object

      Open the Visual Basic Editor and then go up to the menu and click Help ➪ Microsoft Visual Basic for Applications Help. You'll be taken to the Microsoft Developer Network (MSDN) website. While on MSDN, search for the word Range to see the page for the Range object. There you will discover that the Range object exposes three properties that can be used to manipulate your worksheets via VBA.

       The

Скачать книгу