 <p>Reducer should be aware only of a small part of state.</p> <p>Good place for described logic is the action creator. With redux-thunk you will be able to make a decision based on a global state.</p> <pre><code>function selectFilter(enjoys) { return (dispatch, getState) =&gt; { dispatch({type: SELECT_FILTER, enjoys}); // if getState().ui.userList.selected exists in getState().data dispatch({type: SELECT_USER, name: null}); } }; </code></pre>