Alison Balteramp;#039;s Mastering Microsoft Office Access 1002003 [Electronic resources] نسخه متنی

Stepping Through Code

Access 2003 gives you three main options for stepping through your code. Each one is slightly different. The Step Into option enables you to step through each line of code within a subroutine or function, whereas the Step Over option executes a procedure without stepping through each line of code within it. The Step Out option runs all code in nested procedures and then returns you to the procedure that called the line of code you are on. Knowing the right option to use to solve a particular problem is an acquired skill that comes with continued development experience.

Using Step Into

When you reach a breakpoint, you can continue executing your code one line at a time or continue execution until you reach another breakpoint. To step through your code one line at a time, click Step Into on the Debug toolbar, press F8, or choose Debug, Step Into.

The following example illustrates the process of stepping through your code, printing the values of variables to the Immediate window, and modifying the values of variables using the Immediate window.

You can continue the debug process from the breakpoint you set in the previous example. Step two times (press F8). You should find yourself within Func1, about to execute the line of code intTemp = 10 (see Figure 15.7). Notice that VBA did not stop on the line Dim intTemp As Integer. The debugger does not stop on variable declarations.

The code is about to print the Debug statements to the Immediate window. Take a look by opening the Immediate window. None of your code has printed anything to the Immediate window yet. Press F8 (step) three more times until you have executed the line Debug.Print intTemp. Your screen should look like Figure 15.8. Notice the results of the Debug.Print statements.

Now that you have seen how you can display variables and the results of expressions to the Immediate window, take a look at how you can use the Immediate window to modify values of variables and controls. Start by changing the value of intTemp. Click the Immediate window and type

intTemp = 50 . When you press Enter, you actually modify the value of intTemp. Type

?intTemp , and you'll see that Access echoes back the value of 50. You also can see the value of intTemp in the Locals window. Notice in Figure 15.9 that the intTemp variable appears along with its value and type.

Executing Until You Reach the Next Breakpoint

Suppose that you have reached a breakpoint, but you realize that your problem is farther down in the code execution. In fact, the problem is actually in a different function. You might not want to continue to move one step at a time down to the offending function. Use the Procedure drop-down menu to locate the questionable function, and then set a breakpoint on the line where you want to continue stepping. You now are ready to continue code execution until Access reaches this line. To do this, click Continue on the Debug toolbar, press F5, or choose Run, Continue. Your code continues to execute, stopping at the next breakpoint. To see how this works, continue the Debug process with the next example.

NOTE

You also can opt to resume code execution to the point at which your cursor is located. To do this, select Run to Cursor from the Debug menu, or press Ctrl+F8.

Suppose that you realize your problem might be in Func3. You do not want to continue to move one step at a time down to Func3. No problem. Use the Procedure drop-down menu to view Func3, as shown in Figure 15.10. Set a breakpoint on the line that reads Debug.Print "We Are Now In Func3()". You are ready to continue code execution until Access reaches this line. Click Continue on the Debug toolbar, press F5, or choose Run, Continue. Your code continues to execute, stopping on the breakpoint you just set. Press F5 again. The code finishes executing. Return to the Form View window.

Using Step Over

Sometimes you already have a subroutine fully tested and debugged. You want to continue stepping through the routine that you are in, but you don't want to watch the execution of subroutines. In this case, you use Step Over. To step over a subroutine or function, click Step Over on the Debug toolbar, press Shift+F8, or choose Debug, Step Over. The code within the subroutine or function you are stepping over executes, but you do not step through it. To experiment with the Step Over feature, follow the next example.

Click the open form and click the Start Debug Process button one more time. Because you did not remove the existing breakpoints, Access places you on the line of code that reads Call Func1. Select Clear All Breakpoints from the Debug menu, or use the Ctrl+Shift+F9 keystroke combination to remove all breakpoints. Step (press F8) five times until you are about to execute the line Call Func2. Suppose that you have tested Func2 and Func3 and know that they are not the cause of the problems in your code. With Func2 highlighted as the next line Access will execute, click Step Over on the toolbar. Notice that Access executes Func2 and Func3, but that you now are ready to continue stepping in Func1. In this case, Access places you on the End Sub line immediately following the call to Func2.

Using Step Out

You use the Step Out feature to step out of the procedure you are in and to return to the procedure that called the line of code you are on. You use this feature when you have accidentally stepped into a procedure that you realize you have fully tested. You want to execute all the code called by the procedure you are in and then step out to the calling procedure so that you can continue with the debugging process. To test how this works, follow this example.