I created a temporary polygon layer with a column called “class”. This layer is empty, and I want to start adding features in. But I want to limit my class values to be either A, B, or C (enum type).

So I go to layer property and find the “wight type” for column “class” and changed it into value map. To test it out, I gave it one enum called “test” as below:

But why in the editing mode, the class dropdown has “(null)” inside? How to remove it (below)?

If this is not the correct way to configure a column to be enum type, what is the correct way to do so? I do want to start editing the layer from EMPTY, and I want the dropdown set up without null from the beginning. thanks.