React@16.x（57）Redux@4.x（6）- 实现 bindActionCreators

1，分析

一般情况下，action 并不是一个写死的对象，而是通过函数来获取。

而 bindActionCreators 的作用：为了更方便的使用创建 action 的函数 actionCreator。

举例：

1，直接传入函数

const createAddUserAction = (user) => ({
    type: ADD_USER,
    payload: user,
});

store.dispatch(createAddUserAction({ id: 3, name: "name3", age: 20 }));

相当于

const addUser = bindActionCreators(createAddUserAction, store.dispatch);
addUser({ id: 3, name: "name3", age: 20 });

2，传入对象

const actions = {
    addUser: createAddUserAction,
    updateUser: createUpdateUserAction,
    deleteUser: createDeleteUserAction,
};

store.dispatch(actions.addUser({ id: 3, name: "name3", age: 20 }));
store.dispatch(actions.updateUser(2, { name: "name22" }));
store.dispatch(actions.deleteUser(1));

相当于

const bindAction = bindActionCreators(actions, store.dispatch);
bindAction.addUser({ id: 3, name: "name3", age: 20 });
bindAction.updateUser(2, { name: "name22" });
bindAction.deleteUser(1);

2，实现

export const bindActionCreators = (actionCreators, dispatch) => {
    if (typeof actionCreators === "function") {
        return getAutoDispatchActionCreator(actionCreators, dispatch);
    } else if (typeof actionCreators === "object") {
        const res = {};
        for (const key in actionCreators) {
            if (Object.hasOwnProperty.call(actionCreators, key)) {
                const ac = actionCreators[key];
                if (typeof ac === "function") {
                    res[key] = getAutoDispatchActionCreator(ac, dispatch);
                }
            }
        }
        return res;
    } else {
        throw TypeError("actionCreators 必须是函数或对象");
    }
};

function getAutoDispatchActionCreator(actionCreator, dispatch) {
    return function (...args) {
        dispatch(actionCreator(...args));
    };
}

以上。