What is the difference between Sub and Function in

问题:

I am going through some old VB code and I run into function definitions like these -

 Private Function ExistingCustomer(Index As Integer, Customer As String) As Integer

 Private Sub cmdCustomerList_Click()

What's the difference?

回答1:

Function returns value, Sub doesn't. It's that simple.

回答2:

A function can also be used in an expression. A Subroutine cannot. Functions can lend to the readability of your code better than a subroutine.

Here's an example of how a function can increase readability:

If AccountIsLocked("JJones") then Msgbox("This account is locked")

this function would be defined somewhere

public function AccountIsLocked(UserId as string) as boolean
   dim usr = uow.AccountRepository.UserInfo(UserId)
   return usr.locked
end function

Here's the same example but coded with a subroutine:

CheckIfAccountLocked("JJones")

and elsewhere this sub is defined:

public sub CheckIfAccountLocked(UserId)
       if uow.AccountRepository.UserInfo(UserId).locked then
          msgbox("Account is locked")
       end if
end sub

Also note that checking the value is separated from the action -- this contributes to separation of duties. The function would lend toward re-usability.

With VB6 there are some odd rules governing parenthesis. If there are no parameters to a sub then the parenthesis are not needed (I think Visual Studio might remove the parenthesis). One way around this is to add the keyword "Call" before your sub.

Call CheckIfAccountLocked()

vs

CheckIfAccountLocked

回答3:

In function we can return values as boolean, string and other data data types.

but sub does not return any thing. it just executes code and instruction that we give. These are also regarded as methods

Sub is also used in control's events and these events also not return any value.

for example the click event of a command button: Private sub cmd_click()

end sub

回答4:

They are both sections to write code however a function must return a value. For example if you had a program in which a complicated mathematical procedure needs to be executed a number of times you would simply make a function and have the complicated maths code in there and any time you need to do the calculation you can just call the function. Hope this helped not sure if I explained it well.

回答5:

What is the difference between Sub and Function in VB6?

"sub" can perform some action. "sub" returns no value.

Example:

Form_Load()

"function" can also perform some action but it also returns some value to point from which it was called. that is, "Functions return a value, often based on a variable"

Example:

Val(), FormatPercentage().

回答6:

function in vb

• a function must return some value/s
• Syntax : private function fun_name(argument/s(optional)) as return_type(integer,string..) return value end function
• fun_name(arguments(optional) ) is enough for function call

sub in vb

• a sub need not to be return any value/s

• Syntax : private sub sub_name(argument/s(optional))

  end sub

• sub_name(arguments(optional) ) is enough for function call

回答7:

1. Syntax of functions will be Function...End function and for Sub will be Sub...End Sub.
2. Functions may or may not have objects but sub doesn't have objects
3. Functions are re-usable where Sub doesn't
4. Functions can return values but sub doesn't
5. Functions may have object repository but sub doesn't
6. Extension of functions is .qfl where for sub it's .vba

回答8:

A function holds data and code. But a subroutine contains only code, but not data.