我在一个化简器中遇到一个问题,在那里我可以轻松地将所有信息返回到前端,除了一个称为“ items”的数组,我需要进行一次额外的提取以获取更多数据。我在此获取操作中遇到的问题是,它最终会导致返回承诺而不是返回值。我的问题是我如何获得价值而不是承诺? (例如,通过阻止其他所有内容直到诺言解决,然后再将其发回)。
我在下面的代码中都进行了注释,希望可以更清楚地解释所有内容:
export const getItemsForHistory = createSelector(
[getAllHistory, getAllItems, getHistoryPage], (history, items, page) => {
let itemIds = `[a bunch of ids]`;
//this is the call I am making to fetch the additional data for "items"
//this return statement is sending back a promise and not a value
return getUpdatedItems(itemIds, items).then(result => {
//result is the actual value I want
return result;
}, error => {
//if the fetch fails, I would like to send a default value for "items"
//note, if I place this return outside of this entire promise and remove the promise, it works as expected with the default data
return history.map(h => items.get(h.get('item'), null))
}).catch(error => {
return history.map(h => items.get(h.get('item'), null))
})
}
)
//I would like for this method to run asychronously
const getUpdatedItems = async (itemIds, items) => {
let result = await fetchHistoryItemsDetail(itemIds);
return result;
}
const fetchHistoryItemsDetail = (itemIds) => {
let headers = {
"Content-Type": "application/json",
},
fetchUrl = `XXXXXXXXX`;
return fetch(fetchUrl, {
method: "POST",
headers: headers,
body: itemIds,
withCredentials: true,
crossDomain: true,
})
.then(response => {
return response.json();
})
.catch(error => {
throw error;
})
}
export const getSortedHistory = createSelector(
[getAllHistory, getItemsForHistory, getHistorySort, getHistoryPage], (history, items, sort, page) => {
//this is where items is ultimately retured to the front end but it is now a promise and not an array of data
//(from getItemsForHistory)
return sortedEntities(history, items, sort)
}
)
我希望我的问题很清楚,但是如果需要进一步的详细说明,请告诉我。
答案 0 :(得分:0)
您不能从诺言的猫/错误处理程序中返回数据
如果两者都想发送数据,我建议包裹另一个将永远解决的承诺
return new Promise((res) => {
//this is the call I am making to fetch the additional data for "items"
//this return statement is sending back a promise and not a value
getUpdatedItems(itemIds, items).then(result => {
//result is the actual value I want
res(result);
}, error => {
//if the fetch fails, I would like to send a default value for "items"
//note, if I place this return outside of this entire promise and remove the promise, it works as expected with the default data
res(history.map(h => items.get(h.get('item'), null)));
}).catch(error => {
res(history.map(h => items.get(h.get('item'), null)));
})
});