Question

我在React中有一个dataService函数来执行我的API提取。我尝试转换为异步/等待块，但似乎遇到了障碍。

使用承诺：

const dataService = (url, options, dataToPost) => {

    return (dispatch, getState) => {
        const { requestAction, successAction, failureAction } = options.actions;

        if (options.shouldRequest(getState())) {
            dispatch(requestAction());
            const promise = axios.get(url, { withCredentials: true });
            return promise
                .then(response => {
                    if (response.status === 200) {
                        return dispatch(successAction(response, dispatch));
                    }
                    return Promise.reject(response);
                })
                .catch(error => {
                    if (error.response.status === 302) {
                        window.location = '/view';
                    }
                    dispatch(openErrorDialog());
                    return dispatch(failureAction(error));
                });
        }
        return Promise.reject(new Error('FETCHING'));
    };
};

使用异步/等待：

	const dataService = async (url, options, dataToPost) => {

	    return async (dispatch, getState) => {
	        let url;
	        const {requestAction, successAction, failureAction} = options.actions;

	        if (options.shouldRequest(getState())) {
	            dispatch(requestAction());
	            const promise = axios.get(url, {withCredentials: true});
	            try {
	                const response = await promise;
	                if (response.status === 200) {
	                    return dispatch(successAction(response, dispatch));
	                }
	                return Promise.reject(response);
	            } catch (error) {
	                return dispatch(failureAction(error));
	            }
	        }
	        return Promise.reject(new Error('FETCHING'));
	    };
	};

错误是“操作必须是普通对象。将自定义中间件用于异步操作。”。 Promise代码完美无缺。我已经在使用thunk了。请指教。

Answer 1

如果您确实要更改Promise-> async / await，则更改如下：

首先，您不要希望dataService为async，因为这将意味着它返回一个Promise，从而改变了它的调用方式-您不必担心

其次，改变

  const promise = axios.get ...
  promise.then(response ....

到

  const promise = await axios.get ...
  promise.then(response ....

不会工作...

它必须是

const response = await axios.get ...

不需要promise变量

即使如此，您仍仍在转换后的代码中使用承诺 ...现在，这只是由于无缘无故地使用async关键字而有所不同

这是将您的（原始）代码转换为异步/等待的方式

请注意以下内容中“ Promise”一词的总缺失：

const dataService = (url, options, dataToPost) => {

    return async (dispatch, getState) => {
        const { requestAction, successAction, failureAction } = options.actions;

        if (options.shouldRequest(getState())) {
            const data = typeof dataToPost === 'string' ? { data: dataToPost } : dataToPost;
            dispatch(requestAction());
            try {
                const response = dataToPost
                    ? await axios.post(url, data, { withCredentials: true })
                    : await axios.get(url, { withCredentials: true });
                if (response.status === 200) {
                    return dispatch(successAction(response, dispatch));
                }
                throw response;
            } catch(error) {
                if (error.response.status === 302) {
                    window.location = '/view';
                }
                dispatch(openErrorDialog());
                return dispatch(failureAction(error));
            }
        }
        throw new Error('FETCHING');
    };
};

Answer 2

await axios.post(url, data, { withCredentials: true })不返回承诺，它返回请求的真实响应。

在使用async-await时不要使用then-catch，而应使用try-catch。这是解决方法

try {
    const response = dataToPost
        ? await axios.post(url, data, { withCredentials: true })
        : await axios.get(url, { withCredentials: true });
    if (response.status === 200) {
        return dispatch(successAction(response, dispatch));
    }
    return Promise.reject(response);
} catch (err) {
    if (error.response.status === 302) {
        window.location = '/view';
    }
    dispatch(openErrorDialog());
    return dispatch(failureAction(error));
}

将诺言转换为异步/等待-Javascript

2 个答案: