[Redux] Generating Containers with connect() from React Redux (FooterLink)

Code to be refactored:

class FilterLink extends Component {
  componentDidMount() {
    const { store } = this.context;
    this.unsubscribe = store.subscribe(() =>
      this.forceUpdate()
    );
  }

  componentWillUnmount() {
    this.unsubscribe();
  }

  render() {
    const props = this.props;
    const { store } = this.context;
    const state = store.getState();

    return (
      <Link
        active={
          props.filter ===
          state.visibilityFilter
        }
        onClick={() =>
          store.dispatch({
            type: 'SET_VISIBILITY_FILTER',
            filter: props.filter
          })
        }
      >
        {props.children}
      </Link>
    );
  }
}
FilterLink.contextTypes = {
  store: React.PropTypes.object
};

First to create mapStateToProps, It is fairly common to use the container props when calculating the child props, so this is why props are passed as a second argument:

const mapStateToLinkProps = (
  state,
  ownProps
) => {
  return {
    active: ownProps.filter === state.visibilityFilter
  }
}

Second, we need to write mapDispatchToProp function:

const mapDispatchToLinkProps = (
  dispatch,
  ownProps
) => {
  return {
    onClick: () => {
      dispatch({
            type: 'SET_VISIBILITY_FILTER',
            filter: ownProps.filter
          })
    }
  }
}

Last, we need to create connect function, point to the Link compoment:

const FilterLink = connect(mapStateToLinkProps, mapDispatchToLinkProps)(Link);

We can now use the filter link container component and specify just the filter, but the underlying link component will have received the calculated active and on-click values.

-------------

Code:

const todo = (state, action) => {
  switch (action.type) {
    case 'ADD_TODO':
      return {
        id: action.id,
        text: action.text,
        completed: false
      };
    case 'TOGGLE_TODO':
      if (state.id !== action.id) {
        return state;
      }

      return {
        ...state,
        completed: !state.completed
      };
    default:
      return state;
  }
};

const todos = (state = [], action) => {
  switch (action.type) {
    case 'ADD_TODO':
      return [
        ...state,
        todo(undefined, action)
      ];
    case 'TOGGLE_TODO':
      return state.map(t =>
        todo(t, action)
      );
    default:
      return state;
  }
};

const visibilityFilter = (
  state = 'SHOW_ALL',
  action
) => {
  switch (action.type) {
    case 'SET_VISIBILITY_FILTER':
      return action.filter;
    default:
      return state;
  }
};

const { combineReducers } = Redux;
const todoApp = combineReducers({
  todos,
  visibilityFilter
});

const { Component } = React;

const Link = ({
  active,
  onClick,
  children,
}) => {
  if (active) {
    return <span>{children}</span>;
  }

  return (
    <a href='#'
       onClick={e => {
         e.preventDefault();
         onClick();
       }}
    >
      {children}
    </a>
  );
};

const { connect } = ReactRedux;
const mapStateToLinkProps = (
  state,
  ownProps
) => {
  return {
    active: ownProps.filter === state.visibilityFilter
  }
}

const mapDispatchToLinkProps = (
  dispatch,
  ownProps
) => {
  return {
    onClick: () => {
      dispatch({
            type: 'SET_VISIBILITY_FILTER',
            filter: ownProps.filter
          })
    }
  }
}

const FilterLink = connect(mapStateToLinkProps, mapDispatchToLinkProps)(Link);

const Footer = () => (
  <p>
    Show:
    {' '}
    <FilterLink filter='SHOW_ALL'>
      All
    </FilterLink>
    {', '}
    <FilterLink filter='SHOW_ACTIVE'>
      Active
    </FilterLink>
    {', '}
    <FilterLink filter='SHOW_COMPLETED'>
      Completed
    </FilterLink>
  </p>
);

const Todo = ({
  onClick,
  completed,
  text
}) => (
  <li
    onClick={onClick}
    style={{
      textDecoration:
        completed ?
          'line-through' :
          'none'
    }}
  >
    {text}
  </li>
);

const TodoList = ({
  todos,
  onTodoClick
}) => (
  <ul>
    {todos.map(todo =>
      <Todo
        key={todo.id}
        {...todo}
        onClick={() => onTodoClick(todo.id)}
      />
    )}
  </ul>
);

let nextTodoId = 0;
let AddTodo = ({ dispatch }) => {
  let input;

  return (
    <div>
      <input ref={node => {
        input = node;
      }} />
      <button onClick={() => {
        dispatch({
          type: 'ADD_TODO',
          id: nextTodoId++,
          text: input.value
        })
        input.value = '';
      }}>
        Add Todo
      </button>
    </div>
  );
};
AddTodo = connect()(AddTodo);

const getVisibleTodos = (
  todos,
  filter
) => {
  switch (filter) {
    case 'SHOW_ALL':
      return todos;
    case 'SHOW_COMPLETED':
      return todos.filter(
        t => t.completed
      );
    case 'SHOW_ACTIVE':
      return todos.filter(
        t => !t.completed
      );
  }
}

const mapStateToTodoListProps = (state) => {
  return {
    todos: getVisibleTodos(
      state.todos,
      state.visibilityFilter
    )
  };
};

const mapDispatchToTodoListProps = (dispatch) => {
  return {
    onTodoClick: (id) => {
      dispatch({
        type: 'TOGGLE_TODO',
        id
      });
    }
  };
};

const VisibleTodoList = connect(
  mapStateToTodoListProps,
  mapDispatchToTodoListProps
)(TodoList);

const TodoApp = () => (
  <div>
    <AddTodo />
    <VisibleTodoList />
    <Footer />
  </div>
);

const { Provider } = ReactRedux;
const { createStore } = Redux;

ReactDOM.render(
  <Provider store={createStore(todoApp)}>
    <TodoApp />
  </Provider>,
  document.getElementById('root')
);

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>JS Bin</title>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/redux/3.0.4/redux.js"></script>
   <script src="https://fb.me/react-0.14.0.js"></script>
  <script src="https://fb.me/react-dom-0.14.0.js"></script>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/react-redux/4.0.0/react-redux.js"></script>
</head>
<body>
  <div id='root'></div>
</body>
</html>