Default input menu for custom component

Hi all,

I am pretty sure there is a simple answer to this question, but I can't seem to find it in any of the posts.

I am making a few custom c# components and I would like to create an input parameter that displays a list of options for the user to pick from as input.

Basically the input should present a small drop down menu with values to pick from like the construction shown below with a value list that returns an integer to the input based on the chosen option, so in other words I would like to integrate this value list component in the input parameter itself.

I have been looking in the GH_Component.GH_InputParamManager options but all these options give single values, lists or trees, and only show context menu's based on the type (like boolean input has a drop down menu for true/false).

So I was looking at the overriding methods for AppendAdditionalComponentMenuItems but here I can only set a list for the menu of the component itself and not a specific input param.

Do I need to somehow access the GH_ValueList methods in RegisterInputParams to do this?

Any help, or reference to older posts/ Grasshopper SDK would be great!

Thanks in advance!

Cheers Dion

Replies to This Discussion

Permalink Reply by David Rutten on July 8, 2013 at 3:30am

Param_Integer allows you to specify named values. You can use this to provide a list of constants to the user:

Dim param As Param_Integer = getanintegerparameterfromsomewhere()

param.AddNamedValue("Option 1", 0)

param.AddNamedValue("Option 2", 1)

param.AddNamedValue("Option 3", 2)

It's probably best to put this code in the RegisterInputParameters method.

David Rutten

david@mcneel.com

Tirol, Austria

Permalink Reply by Dion Jansen on July 8, 2013 at 4:21am

Hi David, thanks for the quick response!

I looked at the your code but I cannot seem to get it to work as an input parameter.

I tried inside the RegisterInputParams(GH_Component.GH_InputParamManager pManager) method, to cast the Param_Integer 'param' as a default value for the AddIntegerParameter method like so:

Param_Integer param = new Param_Integer();

param.AddNamedValue("option_1", 0);
param.AddNamedValue("option_2", 1);
param.AddNamedValue("option_3", 2);

pManager.AddIntegerParameter("Integer", "I", "input int", GH_ParamAccess.item,(int)param);

Trying to convert it directly to an integer like (int)param troughs the following error:

Error 1 Cannot convert type 'Grasshopper.Kernel.Parameters.Param_Integer' to 'int'

Trying to use either Convert.ToInt32(param) or (IEnumerable<int>)param both builds but upon loading the plugin give me Loading Errors:

Object: myComponent(level 1)

{
Exception has been thrown by the target of an invocation.
TargetInvocationException
}

Object: myComponent(level 2)
{
Unable to cast object of type 'Grasshopper.Kernel.Parameters.Param_Integer' to type 'System.Collections.Generic.IEnumerable`1[System.Int32]'.
InvalidCastException
}

Then I tried the other way around to cast the int to Param_Integer like so:

Param_Integer param = (Param_Integer)pManager.AddIntegerParameter("Input", "I", "List input", GH_ParamAccess.item);

param.AddNamedValue("option_1", 0);
param.AddNamedValue("option_2", 1);
param.AddNamedValue("option_3", 2);

And consistently this gives me the same error but the other way around:

Error 1 Cannot convert type 'int' to 'Grasshopper.Kernel.Parameters.Param_Integer'

I feel like I am looking at this all wrong, any suggestions?

Thanks!

Dion

Permalink Reply by David Rutten on July 8, 2013 at 6:09am

pManager.AddIntegerParameter("Integer", "I", "input int", GH_ParamAccess.item);

Param_Integer param = pManager[0] as Param_Integer;

param.AddNamedValue("option_1", 0);

etc.

David Rutten

david@mcneel.com

Tirol, Austria

Permalink Reply by Dion Jansen on July 8, 2013 at 6:16am

Yes, works like a charm!

Many thanks David!

Dion

Permalink Reply by Jakob Lilliemarck on November 17, 2017 at 10:54am

Can this be done within a ghpython component? Anyone know of any examples of how?

Best

Jakob

Permalink Reply by David Rutten on November 17, 2017 at 12:45pm

No, you have to write your own parameter type for this, it cannot be done in any script components.

Permalink Reply by Jakob Lilliemarck on November 17, 2017 at 1:23pm

Alright, thanks for your reply David. Guess i better look into C#. There is no current way of doing this with Python at all, right?

Permalink Reply by David Rutten on November 17, 2017 at 1:56pm

The script components do not use Integer inputs, which is the only type that supports this by default. So you'll have to either create a custom component in Visual Studio which uses Integer inputs, or create an entirely new type from scratch. Neither is possible in C# scripting, and I assume it isn't possible in Python scripting either.

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