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Sub Procedures
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A sub procedure is a section of code that carries an assignment but
doesn't give back a result. To create a sub procedure, start the section
of code with the Sub keyword followed by a name for the sub procedure. To
differentiate the name of the sub procedure with any other regular name,
it must be followed by an opening and closing parentheses. The section of the sub procedure code closes with
End Sub as follows:
Sub ShowMeTheDough() End Sub
The name of a sub procedure should follow the same
rules we reviewed for the the variables, omitting the prefix:
In the following example, a sub procedure named DisplayFullName is
created. It retrieves fields of two text boxes (first name and last name)
on a form and displays a full name as a result of combining them:
Sub DisplayFullName()
FullName = FirstName & " " & LastName
End Sub
As mentioned already, you can declare variables for
use in your program. In the same way, you can declare variables in the
procedure if you need to. These variables are declared and dealt with in
the same way we learned in the regular script sections. Using declared
variables, the above procedure can be written as follows:
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Sub DisplayFullName()
Dim FirstName, LastName
Dim FullName
FullName = FirstName & " " & LastName
End Sub
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Calling a Procedure
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After creating a procedure, you can call it from another procedure,
function, or control's event in the body section of an HTML file. To call a simple procedure such as the
earlier DisplayFullName, you can just write the name of the sub procedure.
In the following example, the above DisplayFullName
sub procedure is called when the user clicks the Detail section of the
form:
Sub Detailer()
DisplayFullName
End Sub
If you want the procedure to be accessed immediately
as soon as the page displays, you can assign its name to the onLoad()
event of the body tag.
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Arguments
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Passing an Argument
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To carry an assignment, sometimes a procedure needs one or more
values
to work on. If a procedure needs a variable, such a variable is called an
argument. Another procedure might need more that one argument, thus many
arguments. The number and types of arguments of a procedure depends on
various factors.
If you are writing your own procedure, then you will
decide how many arguments your procedure would need. You also decide on
the type of the argument(s). For a procedure that is taking one argument,
in the parentheses of the procedure, write a name for the argument. Here
is an example:
Sub CalculateArea(Radius)
Dim dblPI
Dim dblArea
dblPI = 3.14159
dblArea = Radius * Radius * dblPI
End Sub
A procedure can take more than one argument. If you
are creating such a procedure, between the parentheses of the procedure, write the name of the
first argument followed by a comma; add the second argument and subsequent arguments and close the
parentheses. There is no relationship between the arguments; for example,
they can be of the same type:
Sub CalculatePerimeter(Length, Height)
Dim dblPerimeter
dblPerimeter = 2 * (Length + Height)
End Sub
The arguments of your procedure can also be as varied
as you need them to be. Here is an example:
Sub DisplayGreetings(strFullName, intAge)
Dim Sentence
Sentence = "Hi, " & strFullName & ". You are " & intAge & " years old"
End Sub
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Calling an Argumentative Procedure
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We saw already how to call a procedure that doesn't
take any argument. Actually, there are various ways you can call a sub
procedure. As we saw already, if a sub procedure doesn't take an argument,
to call it, you can just write its name. If a sub procedure is taking an
argument, to call it, type the name of the sub procedure followed by the
name of the argument. If the sub procedure is taking more than one
argument, to call it, type the name of the procedure followed by the name
of the argument, in the exact order they are passed to the sub procedure,
separated by a comma. Here is an example:
Sub Result()
Dim dblHours, dblSalary
CalcAndShowSalary dblHours, dblSalary
End Sub
Sub CalcAndShowSalary(Hours, Salary)
Dim dblResult
dblResult = Hours * Salary
txtResult = dblResult
End Sub
Alternatively, you can use the keyword Call to
call a sub procedure. In this case, when calling a procedure using Call,
you must include the argument(s) between the parentheses. using Call, the
above procedure could call the CalcAndShowSalary as follows:
Sub Result()
Dim dblHours As Double
Dim dblSalary As Double
dblHours = txtHours
dblSalary = txtSalary
Call CalcAndShowSalary(dblHours, dblSalary)
End Sub
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Functions
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Creating a Function
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A function is an assignment that a piece of code can take care for the
functionality of a database. The main difference between a sub procedure
and a function procedure is that a function can return a value.
A function is created like a sub procedure with a few
more rules. The creation of function starts with the Function keyword and closes with
End Function.
Here is an example:
Function FindFullName() End Function
The name of the function follows the same rules and
suggestions we have reviewed for the sub procedures.
To implement a function, remember that it is supposed
to return a value. In the body of the function, describe what it is
supposed to do. to return the right value, assign the desired value to the
name of the function. Here is an example:
Function CalculateArea(Radius)
CalculateArea = Radius * Radius * 3.14159
End Function
A function can also be as complex as performing many
and various expressions in order to get a value that can be assigned to
the name of the function.
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Calling a Function
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To call a function, you have two main alternatives. If you want to use the
return value of a function in an event or another function, assign the
name of the function to the appropriate local variable. Make sure you
include the argument(s) of the function between parentheses.
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