Custom class as input/output parameter in plug-in

Hi all,

I'm trying to write a simple test plug-in.

The plug-in components need to be able to

use objects of a custom class as parameters.

I'm going to derive the component classes from GH_Component

I think I'll have to use

GH_Component.GH_InputParamManager.RegisterParam()

for input and

GH_Component.GH_OutputParamManager.RegisterParam()

for output

Is that right ?

I also think that to use these methods I need to derive

a class from GH_Param

Still right ?

Then I'd like to know which methods/properties need

to be overridden in the derived class.

Any example on this ?

Or some other info ?

... I hope this makes some sense ...

Thanks

Emilio

Replies to This Discussion

Permalink Reply by David Rutten on January 27, 2011 at 12:59pm

Hi Emilio,

not entirely correct. Or rather, not the best way to approach this.

The first thing you'll need to do is write your own data type and make sure it implements IGH_Goo (or derives from GH_Goo<T>). This is probably the hardest task, but it is explained in some detail in the Grasshopper SDK docs (look for the "Simple Data Types" topics in the Examples section).

Once you have your own data type, you could choose to use the Generic parameter to handle it. This will prevent you from storing persistent instances of your data anywhere. If you want to have a parameter that can specifically handle your data type, you'll need to write that as well. You can derive from GH_Param<T>, where T is your new data type. Or you can derive from GH_PersistentParam<T> if you want the ability to store local instances of your data.

Finally, to use your new parameter in a component you need to construct it yourself and pass it to the pManager.RegisterParam() method in RegisterInputParams() and RegisterOutputParams() calls. It is generally a bad idea to add or remove inputs and outputs from a component at a later stage.

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Emilio Morello on January 27, 2011 at 3:33pm