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将承诺转换为async/await-Javascript

async-await promise javascript

arunmmanoharan · 技术社区 · 6 年前

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'));
    };
};

	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'));
	    };
	};

2 回复 | 直到 6 年前

Jaromanda X 6 年前

如果您真的想改变承诺->async/await然后更改如下:

首先,您不希望dataService async

第二,改变

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

到

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

行不通。。。

必须是这样

const response = await axios.get ...

不需要promise变量

仍在使用承诺 异步

下面是如何将(原始)代码转换为async/await

请注意以下内容中完全没有“承诺”一词:

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');
    };
};

Gianfranco Fertino 6 年前

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

使用async await时不要使用then catch,而是使用try catch。这是解决办法

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));
}