如何在redux中更新数量而不重复？

// 定义action
const updateQuantity = (quantity) => {
  return {
    type: 'UPDATE_QUANTITY',
    payload: quantity
  };
};

// 创建reducer函数
const quantityReducer = (state = 0, action) => {
  switch(action.type) {
    case 'UPDATE_QUANTITY':
      return state + action.payload;
    default:
      return state;
  }
};

// 创建store对象
const store = createStore(quantityReducer);

// 连接store和组件
const mapStateToProps = (state) => {
  return {
    quantity: state
  };
};

const mapDispatchToProps = (dispatch) => {
  return {
    updateQuantity: (quantity) => dispatch(updateQuantity(quantity))
  };
};

// 组件
class MyComponent extends React.Component {
  // ...
  handleClick = () => {
    const { quantity, updateQuantity } = this.props;
    updateQuantity(quantity + 1); // 更新数量
  }
  // ...
}

export default connect(mapStateToProps, mapDispatchToProps)(MyComponent);