Redux Thunk的目的`[[[arg（s）]）=> dispatch =>`？

debugcn 发表于 Dev

NattyC

下面的代码来自Brad Traversy在MERN堆栈上的Udemy课程。我是Redux和Redux Thunk的新手，并试图了解其目的=> dispatch =>是什么。我知道它来自Redux Thunk，它是在Redux存储文件中设置的。我认为dispatch在此使用该命令是为了从此函数调度多个动作，并阅读该= ([arg(s)]) => dispatch =>语法是currying的示例（尽管由于curring每个函数都有一个参数，所以这似乎并不正确）。

我非常感谢您的帮助=> dispatch =>。

（其他较小的混乱点：在此过程中，该功能setAlert被称为动作，但是我不确定它是否正确，因为它包含多个动作派遣。）

export const setAlert = (msg, alertType, timeout = 5000) => dispatch => {
  const id = uuidv4();
  dispatch({
    type: SET_ALERT,
    payload: { msg, alertType, id }
  });

  setTimeout(() => dispatch({ type: REMOVE_ALERT, payload: id }), timeout);
};

大卫

这里发生了几件事：

1）setAlert通常称为“动作创建者”。这个函数返回一个动作，您以后可以分派它。

2）Redux-Thunk允许您将表单的功能(dispatch) => {}用作操作（代替更普通的对象表单{ type, payload }）

如果在查看它们如何组合在一起之前单独查看它们，可能会有所帮助：

// This is an action creator (a function that returns an action)
// This doesn't use redux thunk, the action is just a simple object.
// Because it's an action creator you can pass in arguments
// Because it's not a thunk you can't control when then dispatch happens
const setAlertActionCreator = (msg, alertType) => {
  const id = uuidv4();
  return {
    type: SET_ALERT,
    payload: { msg, alertType, id }
  };
};

// You use this as:
dispatch(setAlertActionCreator("msg", "type"));

// This is not an action creator it's just an action.
// This IS a redux-thunk action (it's a (dispatch) => {} function not a simple object)
// Because it's not an action creator you can't pass in arguments to get a custom action back
// Because it IS a redux-thunk action you can dispatch more actions later
const setAlertThunk = (dispatch) => {
  setTimeout(() => dispatch({
    type: SET_ALERT,
    payload: {
      message: "fixed message",
      alertType: "fixed alertType",
      id: "fixed id",
    }
  }), 5000);
};

// You use this as:
dispatch(setAlertThunk);

// When you combine both patterns you gain the ability
// to both pass in arguments and to create additional dispatches
// as the function runs (in this case dispatching again after a timeout.)
// I won't repeat your code, but will show how you would call it:

dispatch(setAlertActionCreator("msg", "type"));

// ie: you use it the same way as example 1.

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