Default values for args

[Dragon]

Hi,

Is there a way to set defaults values for args of a function/sub?

For example:

Function:
public function testFunc (name as string, age as integer = 30, phone as
string)

Calling the Function:
testFunc("John", 25, "555-1212")
testFunc("John", , "555-1212") ' Age will be set to default of 30

This way one or more of arg can be left out and still have a working
function/sub.

Thank you.

 

[Brx]

Your so close, it's Public Function testFunc(name as string, phone as
string, optional age as integer = 30)
Optional parameters must be last in the function, so anything after age must
also be optional.

kmurphy
roughly at nexusinfosys in the com domain.

 

[Herfried K. Wagner [MVP]]

Is there a way to set defaults values for args of a function/sub?

For example:

Function:
public function testFunc (name as string, age as integer = 30, phone as
string)

Calling the Function:
testFunc("John", 25, "555-1212")
testFunc("John", , "555-1212") ' Age will be set to default of 30

This way one or more of arg can be left out and still have a working
function/sub.

You can archieve this behavior with optional parameters:

\\\
Public Sub TestFunc( _
ByVal Name As String, _
Optional ByVal Age As Integer = 30, _
Optional ByVal ID As String = Nothing _
)
...
End Sub
///

 

[Bob Powell [MVP]]

<sigh> I really miss this in C#...

--
Bob Powell [MVP]
Visual C#, System.Drawing

Ramuseco Limited .NET consulting
http://www.ramuseco.com

Find great Windows Forms articles in Windows Forms Tips and Tricks
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Subscribe to the RSS feeds provided and never miss a new article.

 

[Dragon]

Thank you

Your so close, it's Public Function testFunc(name as string, phone as
string, optional age as integer = 30)
Optional parameters must be last in the function, so anything after age
must also be optional.

kmurphy
roughly at nexusinfosys in the com domain.

 

[Dragon]

Is it not available in C#?

<sigh> I really miss this in C#...

--
Bob Powell [MVP]
Visual C#, System.Drawing

Ramuseco Limited .NET consulting
http://www.ramuseco.com

Find great Windows Forms articles in Windows Forms Tips and Tricks
http://www.bobpowell.net/tipstricks.htm

Answer those GDI+ questions with the GDI+ FAQ
http://www.bobpowell.net/faqmain.htm

All new articles provide code in C# and VB.NET.
Subscribe to the RSS feeds provided and never miss a new article.

 

[Herfried K. Wagner [MVP]]

Is it not available in C#?

No, it isn't. However, code written in C# can consume/call methods which
have optional parameters.

 

[Dragon]

Hi,

You can have optional arguments, but they must be the last ones in the
list of arguments, e.g.:

~
Public Function TestFunc (ByVal Name As String, ByVal Phone As
String, Optional ByVal Age As Integer = 30) As BadImageFormatException
~

I would recommend you to have multiple overloaded versions of function
i.e.:

~
Public Function TestFunc(ByVal Name As String, ByVal Phone As
String) As BadImageFormatException
Return TestFunc(Name, Phone, 30)
End Function

Public Function TestFunc(ByVal Name As String, ByVal Phone As
String, ByVal Age As Integer) As BadImageFormatException
REM Your code goes here...
End Function
~

HTH,
Roman

 

[Mythran]

Hi,

Is there a way to set defaults values for args of a function/sub?

For example:

Function:
public function testFunc (name as string, age as integer = 30, phone as
string)

Calling the Function:
testFunc("John", 25, "555-1212")
testFunc("John", , "555-1212") ' Age will be set to default of 30

This way one or more of arg can be left out and still have a working
function/sub.

Thank you.

I don't know why I don't like optional parameters...I think it was because
some other languages don't see those methods when accessing them via COM?
Anywho, a way around it would be:

Public Overloads Function TestFunc(ByVal Name AS String, ByVal Age As
Integer, ByVal Phone As String) As Whatever

End Function

Public Overloads Function TestFunc(ByVal Name As String, ByVal Phone As
String) As Whatever
TestFunc(Name, 30, Phone)
End Function

Public Overloads Function TestFunc(ByVal Name As String)
TestFunc(Name, 30, "555-1212")
End Function

Calls like:

TestFunc("John", 30, "555-1212")
TestFunc("John", "555-1212")
TestFunc("John")

Use overloading to achieve what you want, similarly....

HTH,
Mythran

 

[Dragon]

Thank you Mythran.

I don't know why I don't like optional parameters...I think it was because
some other languages don't see those methods when accessing them via COM?
Anywho, a way around it would be:

Public Overloads Function TestFunc(ByVal Name AS String, ByVal Age As
Integer, ByVal Phone As String) As Whatever

End Function

Public Overloads Function TestFunc(ByVal Name As String, ByVal Phone As
String) As Whatever
TestFunc(Name, 30, Phone)
End Function

Public Overloads Function TestFunc(ByVal Name As String)
TestFunc(Name, 30, "555-1212")
End Function

Calls like:

TestFunc("John", 30, "555-1212")
TestFunc("John", "555-1212")
TestFunc("John")

Use overloading to achieve what you want, similarly....

HTH,
Mythran