Tag: instantiate

Instantiate a Value List Grasshopper component with C#

In a previous post I instantiated a slider automatically using only C#. This means it is possible for a component to add components to your canvas automatically, potentially saving a lot of time in many repetitive workflows.

Here is a similar piece of code, but for the Value List:

C# code

  private void RunScript(bool x, List<object> y, ref object A)
  {
    if(x)
    {
      //instantiate  new value list
      var vallist = new Grasshopper.Kernel.Special.GH_ValueList();
      vallist.CreateAttributes();

      //customise value list position
      int inputcount = this.Component.Params.Input[1].SourceCount;
      vallist.Attributes.Pivot = new PointF((float) this.Component.Attributes.DocObject.Attributes.Bounds.Left - vallist.Attributes.Bounds.Width - 30, (float) this.Component.Params.Input[1].Attributes.Bounds.Y + inputcount * 30);

      //populate value list with our own data
      vallist.ListItems.Clear();
      var item1 = new Grasshopper.Kernel.Special.GH_ValueListItem("Red", "r");
      var item2 = new Grasshopper.Kernel.Special.GH_ValueListItem("Green", "g");
      var item3 = new Grasshopper.Kernel.Special.GH_ValueListItem("Yellow", "y");
      vallist.ListItems.Add(item1);
      vallist.ListItems.Add(item2);
      vallist.ListItems.Add(item3);

      //Until now, the slider is a hypothetical object.
      // This command makes it 'real' and adds it to the canvas.
      GrasshopperDocument.AddObject(vallist, false);

      //Connect the new slider to this component
      this.Component.Params.Input[1].AddSource(vallist);
    }
  }

This code is written for the C# component in Grasshopper. If you are writing components within Visual Studio, there is a little extra work to do in defining GrasshopperDocument and Component, otherwise it’s pretty much a copy-and-paste job too.