firebase n value只能获取一次数据,并且将其放置在React效果中的循环中时不会更新
我的目标是根据客户要求的数据列表获取多个数据,以便我将代码放入使用效果。如果该数组包含客户想要的内容列表,则从服务器中获取这些数据,以便用户可以操纵它。到目前为止,它运行良好,但是当数据库更新时,没有触发OnValue来获取新数据以更新渲染。
这是我的代码。感谢您提前帮助我。
// Getting data
useEffect(() => {
if (empDataArr.length > 1) {
let fromDay = parseInt(dateHandler(startDate).dateStamp);
let toDay = parseInt(dateHandler(endDate).dateStamp);
let tempLogArr = [];
empDataArr.forEach((emp) => {
let qLogEvent = query(child(shopRef(shopId), emp.id + "/log_events"), orderByChild("dateStamp"), startAt(fromDay), endAt(toDay));
// This is the part I need help
onValue(qLogEvent, (snap) => {
let logEventArr = [];
let val = snap.val();
if (val === null) {
} else {
Object.keys(val).forEach((key) => {
let id = key;
let dateStamp = val[key].dateStamp;
let direction = val[key].direction;
let time = val[key].timeStamp + "";
let timeStamp = time.substring(8, 10) + ":" + time.substring(10, 12);
logEventArr.push({ direction: direction, timeStamp: timeStamp, dateStamp: dateStamp, id: id });
});
tempLogArr.push({
id: emp.id,
logEvent: logEventArr,
});
}
});
});
setLogDataArr(tempLogArr.map((x) => x));
}
}, [empDataArr, shopId, startDate, endDate]);
useEffect(() => {
console.log(logDataArr);
}, [logDataArr]);
我尝试使用return onValue()
和const logdata = onvalue()
,但它们不起作用(我不希望前者也可以使用)。
My goal is to get multiple data based on a list of data the customer requested so I put the codes inside useEffect. If the array contains the list of things the customer wants, then it grab those data from the server so the user can manipulate it. So far, it works fine but when the database updates, onValue is not triggered to grab the new data to update the render.
Here is my code. Thank you for helping me in advance.
// Getting data
useEffect(() => {
if (empDataArr.length > 1) {
let fromDay = parseInt(dateHandler(startDate).dateStamp);
let toDay = parseInt(dateHandler(endDate).dateStamp);
let tempLogArr = [];
empDataArr.forEach((emp) => {
let qLogEvent = query(child(shopRef(shopId), emp.id + "/log_events"), orderByChild("dateStamp"), startAt(fromDay), endAt(toDay));
// This is the part I need help
onValue(qLogEvent, (snap) => {
let logEventArr = [];
let val = snap.val();
if (val === null) {
} else {
Object.keys(val).forEach((key) => {
let id = key;
let dateStamp = val[key].dateStamp;
let direction = val[key].direction;
let time = val[key].timeStamp + "";
let timeStamp = time.substring(8, 10) + ":" + time.substring(10, 12);
logEventArr.push({ direction: direction, timeStamp: timeStamp, dateStamp: dateStamp, id: id });
});
tempLogArr.push({
id: emp.id,
logEvent: logEventArr,
});
}
});
});
setLogDataArr(tempLogArr.map((x) => x));
}
}, [empDataArr, shopId, startDate, endDate]);
useEffect(() => {
console.log(logDataArr);
}, [logDataArr]);
I have tried using return onValue()
and const logData = onValue()
but they do not work (and I do not expect the former one to work either).
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