A function is similar to a procedure but the main purpose of the function is to accept a certain input from the user and return a value which is passed on to the main program to finish the execution. There are two types of functions, the built-in functions (or internal functions) and the functions created by the programmers.
10.1 MsgBox ( ) Function
The objective of MsgBox is to produce a pop-up message box that prompt the user to click on a command button before he /she can continues. This format is as follows:
yourMsg=MsgBox(Prompt, Style Value, Title)
The first argument, Prompt, will display the message in the message box. The Style Value will determine what type of command buttons appear on the message box, please refer Table 10.1 for types of command button displayed. The Title argument will display the title of the message board.
|Table 10.1: Style Values
We can use named constant in place of integers for the second argument to make the programs more readable. In fact, VB6 will automatically shows up a list of names constant where you can select one of them.
Example: yourMsg=MsgBox( “Click OK to Proceed”, 1, “Startup Menu”)
and yourMsg=Msg(“Click OK to Proceed”. vbOkCancel,”Startup Menu”)
are the same.
yourMsg is a variable that holds values that are returned by the MsgBox ( ) function. The values are determined by the type of buttons being clicked by the users. It has to be declared as Integer data type in the procedure or in the general declaration section. Table 10.2 shows the values, the corresponding named constant and buttons.
Table 10.2 : Return Values and Command Buttons
|Value||Named Constant||Button Clicked|
| Example 10.1
i. The Interface:
You draw three command buttons and a label as shown in Figure 10.1
|ii. The procedure for the test button:
When the user click on the test button, the image like the one shown in Figure 10.2 will appear. As the user click on the OK button, the message “Testing successful” will be displayed and when he/she clicks on the Cancel button, the message “Testing fail” will be displayed.
|To make the message box looks more sophisticated, you can add an icon besides the message. There are four types of icons available in VB as shown in Table 10.3
|Example 10.2 You draw the same Interface as in example 10.1 but modify the codes as follows:
10.2 The InputBox( ) Function
|An InputBox( ) function will display a message box where the user can enter a value or a message in the form of text. The format is
myMessage is a variant data type but typically it is declared as string, which accept the message input by the users. The arguments are explained as follows:
i. The Interface
|ii. The procedure for the OK button
When a user click the OK button, the input box as shown in Figure 10.5 will appear. After user entering the message and click OK, the message will be displayed on the caption, if he click Cancel, “No message” will be displayed.