/* Accordion.re */
type expanded =
  | Closed
  | Open(string);

type state = {expanded};

type action =
  | Toggle(string);

let component = ReasonReact.reducerComponent("Accordion");

let make = (~render, _children) => {
  ...component,
  initialState: () => {expanded: Closed},
  reducer: (action, state) =>
    switch (action) {
    | Toggle(id) =>
      switch (state.expanded) {
      | Open(x) when x === id => ReasonReact.Update({expanded: Closed})
      | Open(_) => ReasonReact.Update({expanded: Open(id)})
      | Closed => ReasonReact.Update({expanded: Open(id)})
      }
    },
  render: self => {
    let toggle = (id, _evt, self) => self.ReasonReact.send(Toggle(id));

    ...
        {render(self.state.expanded, self.handle, toggle)}
	  ...
  },
};

/* Consumer.re */
...

let print = id => fun
	| Open(open) when open === id => "true"
	| Open(_) => "false"
	| Closed => "false";

let make = _children => {
  ...component,
  render: _self =>
    <Accordion
      render=((expanded, handle, toggle) =>
        ...
          <button onClick=(handle(toggle("item-1-id"))> (ReasonReact.string("open " ++ print("item-1-id"))) </button>
        ...
          <button onClick=(handle(toggle("item-2-id"))> (ReasonReact.string("open " ++ print("item-2-id"))) </button>
        ...
    />
...