BA394 VBScript Lecture 4

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BA394 VBScript Lecture 4

• Tim Faltemier

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In this Lecture

• Look into the use of Subroutines and Functions
  for cleaner code.
• Session Variables
• Look at any issues with your projects that will
  be due next week.

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Sub Routines (Procedures)

• The purpose of Sub routines is to allow the
  programmer to reuse code throughout his or her
  program.
• A Sub routine can be seen in many forms. The
  most common of which would probably be the
  Response.write() sub.
• To understand a little more about the Sub
  routine, you must first know about arguments and
  returns.

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Arguments

• An Argument is simply something in the sub code
  that allows another particular sub or function to
  get data from another location (usually outside
  the sub)
• A typical Sub would look like the following
• Sub DoMultiply(Value1, Value2)
• In the previous example, Value1 and Value2 can be
  anything that the caller wants them to be (1,2)
  etc..

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Returns

• Returns work in a very similar way to a sub but
  in the opposite direction. A Return is something
  that your FUNCTION will send back to the program
  when it is done.
• For example If you call the function
  DoMultiply(Value1, Value2) with the values (2, 4)
  it would Return 8 to the location that called it.

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Sub Routines (II)

• Now that you understand arguments and returns, we
  can get a little further. Sub routines have NO
  return value. Whatever they do / change, they do
  it INSIDE its code.
• So in order to use these effectively, you should
  either call them to change something on the
  screen (write different values etc..) or to
  change Global Variables.
• You can see the example syntax of a Sub on the
  next slide.

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Sub Routine Syntax

• The syntax is as follows (without the lt and gt)
• Sub ltMySubNamegt (ltArg1gt, Arg2, etc..)
• ltsome code goes heregt
• ltsome more code goes heregt
• ltall the code you wantgt
• End Sub
• Note you can have as many arguments as you want!

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Functions

• Now that you hopefully understand Sub routines,
  Functions will be simple.
• The only thing that separates Functions and Subs
  is the fact that Functions return a value to the
  user.
• Most of the time is is better to use Functions
  rather than subs because you can always use the
  value that it returns.

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Functions (II)

• In the worse case scenario (you can not think of
  something to return) return either true or false
  to tell you if the function worked correctly.
• Doing this will save you HUGE amounts of time
  during debugging.
• You can see the syntax of a Function on the next
  page (Note it looks JUST like a Sub but watch
  the detail on the bottom of the page.)

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Functions (III)

• Note that the function definition is usually All
  on the same line.
• Function ltMySubNamegt (ltArg1gt, Arg2, etc..)
• ltsome code goes heregt
• ltsome more code goes heregt
• ltMySubNamegt True or False or equal to any
  variable that you want it to be that you want to
  return.
• End Function

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Session Variables

• If you have ever programmed before and know what
  the concept of global variables are, then you
  know what session variables are.
• Session variables are no different from normal
  variables in most aspects, the only difference is
  that they are stored as long as the user is on
  your site or has the browser open.
• Session variables come in the form
• Session(ltMyVARgt) ltMyValuegt

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Questions or Comments
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Final Notes

• For the next quiz, make sure you look at and
  understand all of the examples from my site and
  read the lecture notes.
• Also make SURE you check back on the website
  before the quiz next week as there may be changes
  noted etc..
• Finally if you have any other questions or
  problems dont hesitate to email me.