How To Use the Assert Method for Debugging

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Article ID: 161153 - View products that this article applies to.
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SUMMARY

The Assert method of the Debug object allows monitoring of an expression for failure conditions.

MORE INFORMATION

The following syntax is used for the Assert method:
Debug.Assert (expression)
The Assert method syntax has the following object qualifier and part:
      Part            Description
      ----            -----------
      Debug           Required. The Assert method only applies to the
                      Debug object.

      expression      Required. Any logical expression.
				
The Assert method forces a design-time break at the Assert statement when the expression evaluates to False. If the expression evaluates as True, program operation continues. For example:
      Function myFunction (x as Long,y as Long, z as Long) as Long
          Debug.Assert (x<>0 And y<>0 And z<>0)
          myFunction = 1/x + 1/y + 1/z
      End Function
				
If you call myFunction as:
      q = myFunction (1,2,3)
				
the program continues as normal. However, passing a zero as any one of the parameters forces a break. The following example breaks at the Assert statement:
      q = myFunction (1,0,3)
				
The above example allows testing for inappropriate parameters to protect against a division by zero error. If a break occurs at the Assert statement, you can check the locals window to determine which value is inappropriate. This is especially useful when the argument values come from other functions:
     q = myFunction ( calcX(), calcY(), calcZ() )
				
The Assert method is only used for debugging. During compiling, Microsoft Visual Basic always removes Assert statements from the final code. There is no workaround for this behavior.

Properties

Article ID: 161153 - Last Review: July 13, 2004 - Revision: 3.1
APPLIES TO
  • Microsoft Visual Basic 6.0 Learning Edition
  • Microsoft Visual Basic 6.0 Professional Edition
  • Microsoft Visual Basic 6.0 Enterprise Edition
  • Microsoft Visual Basic 5.0 Control Creation Edition
  • Microsoft Visual Basic 5.0 Enterprise Edition
Keywords: 
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