The document discusses passing arguments by reference versus by value in VBScript functions. It provides two sample functions, one that passes an argument by reference and one that passes by value. It then asks the reader to predict the output of calling each function and explains that passing by reference allows the function to modify the original variable, while passing by value uses a copy of the variable local to the function.

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Here is a QTP quiz for you. We have two functions below. For the first one, argument is
passed by reference while for the second, argument is passed by value.
A. Argument is passed by Reference
Function learnqtp( ByRef var)
myname= "jain"
msgbox var
msgbox myname
End Function
myname= "ankur"
call learnqtp (myname)
B. Argument is passed by Value:
Function learnqtp( ByVal var)
myname= "jain"
msgbox var
msgbox myname
End Function
myname= "ankur"
call learnqtp (myname)
Without copying the functions in your QTP editor, try to find:
1. Output of A.
2. Output of B.
Why do you think output differ/doesn’t differ? Give your answers in comment below.
Now, open QTP and check your answers. Any more comments?
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7 comments ↓
#1 Percy Bell on 11.03.08 at 7:17 am
A:
jain
jain
B:
ankur
jain
Passing by Value is just that. It passes a value to the function to use. It creates a
new space to hold this value.
Passing by Reference passes the pointer to the memory space for the variable.
This means that anything you do to the variable in the function changes the actual
value of the passed variable. This means that if you changed the variable in the
function it will be changed outside the function too.
#2 Zecty on 11.03.08 at 10:11 am
The output will be different. The first code (byRef), will output the name “jain”
twice. Because, when a variable is passed by reference, both the variable “var”
(passed as a parameter) and “myname” (used inside the function) will point to the
same memory space. Since “myname” was not declared (“dim”) inside the
function, when a variable is passed by reference in vbscript, use of the variable
name refers to the calling scope’s use of the variable. But when passed by value
(byVal), the “myname” variable used inside the function and the “var” parameter,
will both be ‘local variables’ that are instantiated only for the life of the function,
and do not affect the memory area used by the ‘global’ “myname” variable.
This shows why it is a good reason to always declare variables!

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