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TOPIC: Calling a class that has no public constructor

Calling a class that has no public constructor 2 years 3 weeks ago #1

  • jpmaertens
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How can I solve this ? The Vegas class has no public constructor

#using ScriptPortal.Vegas

FUNCTION Start( ) AS VOID
LOCAL oVegas AS Vegas

oVegas:=Vegas{}

error XS1729: 'Vegas' does not contain a constructor that takes 0 arguments

Vegas is a class part of the video-edting software Sony Vegas,

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Calling a class that has no public constructor 2 years 3 weeks ago #2

  • Phil Hepburn
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The message says it does not have a constructor which takes zero arguments - BUT - the does not mean that it has no constructor.

Try supplying one or more nulls !?

Just a thought off the top of my head.

Cheers,
Phil.

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Calling a class that has no public constructor 2 years 3 weeks ago #3

JP,

What Phil said, or there is a static method in the class or a static property that allows you to create/access instances.

Robert
XSharp Development Team
The Netherlands
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Calling a class that has no public constructor 2 years 3 weeks ago #4

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When I right click on the Vegas{} to see the parameters, it says it has no public constructor.

Of course I tried with 1...4 null parameters, the resulting error is : it has no constructor with 1..4 parameters.

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Calling a class that has no public constructor 2 years 3 weeks ago #5

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I tried to do this simple test

cTest:=Vegas:Version

the Xide interface shows all methods and accesses of Vegas when I type the :

This however gives another compiler error :

error XS0120: An object reference is required for the non-static field, method, or property 'Vegas.Version'

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Calling a class that has no public constructor 2 years 3 weeks ago #6

Jean-Pierre,

you have to type:
cTest := Vegas.Version to access a Static-Class member

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Calling a class that has no public constructor 2 years 3 weeks ago #7

  • jpmaertens
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Thank you, but does not work either.

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Calling a class that has no public constructor 2 years 3 weeks ago #8

Hi Jean-Pierre,
that's the kind of scenario where you don't need to call the constructor, either :
. because you must use a static Method that will always return the same Vegas object that is created internally, so you have a Singleton
. because you will receive the Vegas object when your code is called by the application that will consume your extension (Here that's my favorite option)

Hope this helps.

Cheers,
Fabrice

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Calling a class that has no public constructor 2 years 3 weeks ago #9

Hi Jean-Pierre,

It is a bug of XIDE that it shows members on "Vegas:", ":" is used on instances of types only, is not valid on types themselves, so this should show nothing. But try a dot instead, to see the static members of the class, with "Vegas.", does the list now contain an entry like "Create", "CreateInstance" or something like that?

In any case, as others already pointed out, the fact that there does not exist a public constructor means that the developer of the class did not intend (and does not allow) to let the programmer create an instance of this class directly. Instead they must have provided another means of getting such an instance, but it's too hard to say how, without some documentation or without looking at the full contents of the dll in a disassembler like ILSpy or Reflector. Is there some documentation for this library? If not, would it be possible to zip and upload it for us to have a look?

Chris
XSharp Development Team
chris(at)xsharp.eu

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Calling a class that has no public constructor 2 years 3 weeks ago #10

  • jpmaertens
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Hello Fabrice,

I was just trying to translate a c# sample.
this is the sample :

using System;
using System.Text;
using System.Windows.Forms;
using ScriptPortal.Vegas;

namespace SampleScript1
{
public class EntryPoint
{
public void FromVegas(Vegas vegas)
{
MessageBox.Show(vegas.Version);
}
}
}

That is all. I can't generate code to run inside Vegas, when I have compiler errors. It is also very puzzling because when I type Vegas: the IDE shows me all the methods and accesses of Vegas.


#using System
#using System.Windows.Forms
#using ScriptPortal.Vegas


FUNCTION start() AS VOID

MessageBox.Show(Vegas:version) // error XS0120: An object reference is required for the non-static field, method, or property 'Vegas.Version'

RETURN

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Calling a class that has no public constructor 2 years 3 weeks ago #11

Hi Jean-Pierre,

Ahh, I love seeing c# code, it is so clear to read...

Well, this method declaration in the c# code:

public void FromVegas(Vegas vegas)

defines the FromVegas() method with one parameter, named vegas and its type is Vegas (I know...). The equivalent VO/x# definition would be:

METHOD FromVegas(vegas AS Vegas) AS VOID

So the c# code MessageBox.Show(vegas.Version) operates on the "vegas" local (parameter), not on the "Vegas" (with capital V) type itself. In VO/x# syntax again, this would be:

MessageBox.Show(vegas:Version)

so this should compile fine in x:

METHOD FromVegas(vegas AS Vegas) AS VOID
MessageBox.Show(vegas:Version)

or I would suggest to change the parameter name to something else, so it is more clear what the code does, something like (for example):

METHOD FromVegas(oVegas AS Vegas) AS VOID
MessageBox.Show(oVegas:Version)

the reason why you get a compiler error in this code:

FUNCTION start() AS VOID
MessageBox.Show(vegas:version)

is that there is no variable named "vegas" defined in this function, so the compiler thinks that you are attempting to call a static method on the same named "Vegas" class itself. If you had defined a "LOCAL vegas AS Vegas", then it would again compile fine, but would obviously fail at runtime, because "vegas" (the var...) would be NULL.

Chris
XSharp Development Team
chris(at)xsharp.eu

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Calling a class that has no public constructor 2 years 3 weeks ago #12

  • jpmaertens
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Thank you very much Chris !! This compiles without errors.

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Calling a class that has no public constructor 2 years 3 weeks ago #13

  • Phil Hepburn
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Hi you guys,

Now you may understand why I can't count properly any more!

Or why I code like NASA folks programmer their Lunar/Mars probes ;-0)

Recently I spent a few consecutive days translating code directly from C# into X#. It does get easier - BUT - at least my C# code did not have the irritating "vegas / Vegas" sorts of confusion.

Personally I find this (too often) common style of coding 'name choice' VERY unclear, even when it is syntactically correct - or should that be semantically correct ?

Either way, onward and upward, and X# syntax for Leonardo and his mates !!!

Regards,
Phil.

P.S. I really use the single dot a lot in my CORE apps - so much easier (and possibly sloppier too).

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Calling a class that has no public constructor 2 years 3 weeks ago #14

Hi Jean-Pierre,

from Vegas pro Scripting API

from here
www.vegascreativesoftware.com/de/downloads/#c24726
download link
www.vegascreativesoftware.com/fileadmin/...as_scripting_api.zip

Vegas Class
Represents the Vegas application. You can get access to this singleton object via DomainManager.VegasDomainManager.GetVegas()

HTH

Frank

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Calling a class that has no public constructor 2 years 3 weeks ago #15

  • jpmaertens
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Thank you Frank ! I already made a dll that can be called by Sony Vegas, and thanks to the help I got on this forum, it works (does nothing great for the moment ;-))
Wish I had the professional version of Visual Studio, because the Community version doesn't have the option to start an external program through the debugger, and neither has Xide I think. As I am a retired programmer I can no longer deduct the costs of buying such software (650 €) from my tax bill.

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Calling a class that has no public constructor 2 years 3 weeks ago #16

Jean-Pierre,

In XIDE you can connect to an external process to start debugging your code inside another app:
- Set a breakpoint in your code
- Choose 'Attach to Process' in the Debug menu
Then the debugger should stop as soon as your breakpoint is reached.


Robert
XSharp Development Team
The Netherlands
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