How do I share an enum definition between contracts?

Question

I have two related contracts, let's call them Supplier and Producer.

A Supplier can have a State of inactive, active, or kaput, but only active suppliers can be added to a Producer.

So something like this:

contract Supplier {
  enum State { inactive, active, kaput }
  State constant DEFAULT_STATE = State.inactive

  State public status;

  function Supplier() {
    status = DEFAULT_STATE;
  }
}

But doing this doesn't work.

contract Producer {
  function addSupplier(Supplier _supplier) {
    require(_supplier.status == Supplier.State.active);
  }
}

I considered using an Interface but enum is specifically disallowed in an Interface.

How do I expose enum definitions to external contracts without resorting to something ugly like require(uint(supplier.status) == 1);

Answer 1

Enums defined inside a contract are by default accessible from other contracts. In Producer you can use the expressions:

• Supplier.State.inactive

• Supplier.State.active

• Supplier.State.kaput

Your code is not working because public state variables behave like functions from the perspective of other contracts. Try replacing this line:

require(_supplier.status == Supplier.State.active);

with this:

require(_supplier.status() == Supplier.State.active);