FIT 100

Lab 9: Creating Sign Finder

Autumn 2001

Recommended Reading for Lab 9:

· p. 394-412 (to top of page) in Chapter 8 and p. 681- 689 (Error Handling) in Chapter 14 of Learn to Program with Visual Basic 6.0

OR

· How to Use Visual Basic, Chapters 7, 11

http://library.books24x7.com/toc.asp?bkid=888
This link will be active through November 12, 2001.

You have to be on campus, or coming in through the UW proxy server, to access the page.

Introduction:

Today you create a program and call it SignFinder. In this program, a user will click on the radio button for the month of their birth but they will enter the exact date of their birth as well. When the OK button is clicked, the program will have to decide which sign to display depending on where their birth date falls in the month.

Objectives:

• To understand the importance of object names when changing properties and assigning values with code.
• To be precise in the declaration of variables and understanding how to assign values to them.
• To take input from an unknown user and assign that value to a variable and use it as part of the logic of the program.
• To steadily add pieces of code to your program and increase it’s complexity.

TO DO: 

1. Create a folder on the C drive called Lab9. Save the project and form in this location later.

2. Open up Visual Basic.
   
   

If you have created a form and all the required controls for Lab 9 already, download it from Dante into the Lab9 folder. Then go to that project and open it up.

If you have not created the form yet, open a new Standard EXE and in the form, enter the following controls:

Your form (the interface) for this lab will require the following objects:

2 labels

2 command buttons

1 text box

12 option buttons (radio buttons)

The interface may look similar to the one below, but use whatever colors and setup that works for you:

**A good way to keep track of the names would be to print out the figure
above and put the name you will give each control next to its image**

3. You will want to make the captions of the labels and option buttons similar to the interface above. The names of each object should be meaningful to you so that as you code, you will be able to identify them properly in the statements.
   
   For example, a good name for the label giving the user the information to enter their birth information might be: lblEnter
   
   A good naming scheme for the radio buttons would be to start each with “opt” and follow it with the month they identify. An example for the January button would be: optJan

Name the controls (objects) that are left with names that are usable for you. A suggested naming convention would be the following:

Object Type Name starts with
Form frm

Command Button cmd
Text Box txt
Label lbl
Option Button opt
Picture Box pic
CheckBox chk

Timer tmr

4. Change the font colors and background colors to something pleasing.

5. Save your project as SignFinder and the form as frmSignFinder to the Lab9 folder.
   
   
6. Once you have the form (interface) taken care of, it’s time to deal with the logic – the code.
   
   The detailed logic of the program is as follows:
   
   A user runs your program at their computer. The form pops up and they are requested to select the option button that states the month of their birthday and to enter an integer value that is their birth date. Once they have done this, they click on the OK command button and a label will appear on the form that states their Zodiac sign.
   
   The problem the programmer encounters is that the signs of the Zodiac do not have a one to one correspondence with each month. Depending on the day involved in any month, a person may be one of two signs. This calls for a conditional to help the program decide.
   
   But first, there are a number of things to consider:
   
   Where do you store the Zodiac values?

Every month will potentially have 2 to choose from.
Where do you store the input from the user?
Where do you store the date for each month that will determine whether a user is one sign or another?

Create variables to store the values.

7. Declare 4 separate variables at the top of your program after you enter the Option Explicit statement:

The first variable will hold the Zodiac sign value for the lower half of each month and be a string data type: loSign

The second variable will hold the Zodiac sign value for the upper half of each month and be a string data type: hiSign

The third variable will hold the value of the day each month when the signs change and be an integer data type: changeDay

The fourth variable will hold the value entered by the user that is their birth date and be an integer data type: birthDay

8. In each option button click event, assign the correct sign values to the loSign, hiSign and changeDay variables:

Month loSign hiSign changeDay

January Capricorn Aquarius 19

February Aquarius Pisces 18

March Pisces Aries 20

April Aries Taurus 19

May Taurus Gemini 20

June Gemini Cancer 20

July Cancer Leo 22

August Leo Virgo 22

September Virgo Libra 22

October Libra Scorpio 22

November Scorpio Sagittarius 21

December Sagittarius Capricorn 21

9. Where do you go from here? If a user clicks on any of the radio buttons, the values will be assigned to the variables correctly. Now it’s time to work with the OK button click event. Most of the program logic occurs here.

10. In the cmdOK_Click() event do the following:
    1. Assign the value the user enters into the text box to the variable birthDay. To get to the value entered in the text box, access the Text property.
       
       
    2. Make the label which will display the person’s sign and Go Again command button appear and the text box and OK button disappear. Set the visibility properties to true or false where needed.

3. Write a general conditional that will check to see if the value the user has entered is greater than the changeDay.
   
   If it is, then the label that you are using to display the Zodiac sign should display “Your sign is ” & hiSign “!” in the caption.
   
   If it isn’t greater than changeDay, then the caption will read: “Your sign is ” & loSign “!”
   
   

The & symbol is used to concatenate string values together [place them together, side by side]. If a value in a variable is an integer, it is converted to a string value for purposes of concatenation.

11. In the Go Again button click event, write the appropriate statements to make the labels and text boxes and buttons appear again to start the program over.

12. Save your project.

13. Run your project. Is everything working? What happens if the user enters a letter instead of an integer?

Simple Error Trapping

Often the user will not enter the information we (as programmers) wish them to enter. If they do, for example, enter letters when we expect numbers and we haven’t planned for it, it will stop our program. One form of Error Trapping is to let the user know they have entered incorrect information and ask them to enter it again.

14. The syntax used to start an Error Trap statement is the following:

Private Sub ….. (this could be any event procedure)

On Error GoTo <name of error handler>

<other code statements in the procedure>

Exit Sub

<name of error handler>

<statements to be executed when error occurs>

End Sub

15. The best place to trap any errors in this program is in the OK button click event, since all the other logic is taking place there as well. Call the error handler CheckInput, since it is checking input. You will use a Message box in the error handler statements as a way to alert the use to change their input. The code for the error handler is in color and bold below.
    
    Remember, if you haven’t used the same variable names and object names IT’S OK! Your code will look different from the statements below that aren’t in bold:

Private Sub cmdOK_Click()

On Error GoTo CheckInput

birthDay = txtUserInput.Text

If birthDay > changeDay Then

lblZodiac.Visible = True

lblZodiac.Caption = "Your sign is " & hiSign & "!"

Else

lblZodiac.Visible = True

lblZodiac.Caption = "Your sign is " & loSign & "!"

A Message Box is used in VB 6 to communicate with the user. It can alert them to enter valid data, confirm an action or simply keep the user informed. Here the box will use an “OK” button as a way to let the user confirm the message.

End If

cmdOK.Visible = False

cmdGoAgain.Visible = True

txtUserInput.Visible = False

Exit Sub

CheckInput:

MsgBox "Please enter a valid date and check a month" , VBOKOnly

txtUserInput.SetFocus

End Sub

16. Run your program. What happens if you enter a letter now?
    
    
17. What happens if you enter a number that is negative or above the days in the month? The error trap doesn’t yet have a way to account for that, so add another conditional to take care of those potential errors.
    
    The statement to add (if you have used the correct variable names) is in bold below. Notice the Error Trap name is in red:

birthDay = txtUserInput.Text

If birthDay < 1 Or birthDay > 31 Then GoTo CheckInput

If birthDay > changeDay Then

lblZodiac.Visible = True

lblZodiac.Caption = "Your sign is " & hiSign & "!"

Else

lblZodiac.Visible = True

lblZodiac.Caption = "Your sign is " & loSign & "!"

End If

The bold code statement above now checks to see that the number a user enters is inside of a certain range (between 1 and 31). If it isn’t, the message box comes up again and tells them to check their input. This error trap isn’t perfect (what about months with less than 31 days?), but I’ll let you add to the code to perfect it if you like!

18. Run your program again. Try to enter information that will “break” it. Can you do it?

19. Make SignFinder executable when you are finished and happy with it. Save your project and FTP the entire Lab9 folder containing your project, form and executable to your Dante account. Show the executable to your TA at the beginning of Lab 10.

READ YOUR PROJECT DESCRIPTION for Part 1 of Project 2! You should be able to figure out how to do Part 1 easily after having done this lab.