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Clearly Visual Basic: Programming with Visual Basic 2008. Chapter 18 Talk To Me. Objectives. Explain the difference between a sub procedure and a function procedure Create a function procedure Invoke a function procedure. What’s the Answer?. Function procedure
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Clearly Visual Basic: Programming with Visual Basic 2008 Chapter 18 Talk To Me
Objectives • Explain the difference between a sub procedure and a function procedure • Create a function procedure • Invoke a function procedure Clearly Visual Basic: Programming with Visual Basic 2008
What’s the Answer? • Function procedure • Returns a value after performing its assigned task • Can receive information either by value or by reference • Information it receives is listed in the parameterList in the header • Sub procedure • Does not return a value Clearly Visual Basic: Programming with Visual Basic 2008
What’s the Answer? (continued) • After creating a function: • You can invoke it from one or more places in an application’s code • To invoke a function: • Include the function’s name, along with any arguments, in a statement • Usually the statement that invokes a function will assign the function’s return value to a variable • May also use the return value in a calculation Clearly Visual Basic: Programming with Visual Basic 2008
Price Calculator Application • Figure 18-3 • Shows the Price Calculator application’s user interface • The variables in a function’s header • Have procedure scope Clearly Visual Basic: Programming with Visual Basic 2008
Revisiting the Total Due Calculator Application Figure 18-8 Shows interface for the Total Due Calculator application from Chapter 17 Figure 18-9 Shows the code entered in both the AssignDiscount sub procedure and btnCalc control’s Click event procedure in Chapter 17 Most programmers: Pass a variable by reference only when a procedure needs to produce more than one result Clearly Visual Basic: Programming with Visual Basic 2008
Summary • You can create your own function procedures, called functions • Return statement • Appears as the last statement in a function • Invoke a function by: • Including the function’s name, along with any arguments, in a statement Clearly Visual Basic: Programming with Visual Basic 2008
Summary (continued) • The statement that invokes a function may: • Assign the return value to a variable • Use the return value in a calculation • Display the return value • The following have procedure scope • Variables that appear in a function header’s parameterList • In most cases: • Better to use a function rather than a sub procedure that passes a variable by reference Clearly Visual Basic: Programming with Visual Basic 2008
