如何使用Firebase Cloud功能在DataSnapshot中查找特定值 [英] How to look for a specific value in a DataSnapshot with Firebase Cloud Functions
问题描述
我正在尝试创建一个将在HTTP请求(在计时器上发送)上触发的云函数，该函数将删除具有特定值的所有子项.
I'm trying to make a cloud function that will trigger on HTTP request (which is sent on a timer), that will remove all childs with a specific value.
数据库节点如下所示:
activities
4GI1QXUJG0MeQ8Bq19WOdCQFo9r1 //uid
activity: "hammer"
id: some ID
note: "some note"
timestamp: some timeintervalsince1970
7IDUiufhiws8939hdfIUHiuhwdi5
etc....
我想浏览所有活动，如果活动值为"hammer"，我想删除该孩子.
I want to look through all the activities, and if the activity value is "hammer", I want to remove the child.
这是我到目前为止所拥有的
This is what I have so far
exports.deleteHammerNotifications = functions.https.onRequest((req, res) => {
admin.database().ref('activities').once('value', (snapshot) => {
console.log(snapshot.val())
});
});
打印:
{
'4GI1QXUJG0MeQ8Bq19WOdCQFo9r1':
{ activity: 'nn',
id: '4GI1QXUJG0MeQ8Bq19WOdCQFo9r1',
note: 'Blank note...',
timestamp: 1498032472 },
M6xQU5XWTEVbSqBnR3HBAEhA9hI3:
{ activity: 'hammer',
id: 'M6xQU5XWTEVbSqBnR3HBAEhA9hI3',
note: 'some note here...',
timestamp: 1497973839 },
}
我的问题是我不知道如何循环遍历DataSnapshot并查找具有以下活动的所有子项:"hammer"值. 我已经在数组的xcode项目中完成了类似的功能，但是我不知道如何使用JavaScript.
My problem is I don't know how to cycle through the DataSnapshot and look for all the childs that has the activity: "hammer" value. I have done similar function in my xcode project with arrays, but I don't know how to do it with JavaScript.
感谢您的帮助！
推荐答案
要在匹配的子节点之间循环，请使用snapshot.forEach():
To cycle through the matching child nodes, use snapshot.forEach():
exports.deleteHammerNotifications = functions.https.onRequest((req, res) => {
admin.database().ref('activities').once('value', (snapshot) => {
snapshot.forEach((childSnapshot) => {
console.log(childSnapshot.val())
});
});
});
但是您仍然缺少查询以选择正确的节点.如果没有这样的查询，您可能会调用admin.database().ref('activities').remove().
But you're still missing a query here to select the correct nodes. Without such a query you might as well call admin.database().ref('activities').remove().
要最有效地从数据库中删除多个项目并将单个响应写回用户，请使用此功能(我从最近需要的功能中修改了此功能):
To most efficiently delete a number of items from the database and write a single response back to the user, use this function (which I modified from something I needed recently):
exports.cleanup = functions.https.onRequest((req, res) => {
var query = admin.database().ref("activities").orderByChild("activity").equalTo("hammer");
query.once("value").then((snapshot) => {
console.log("cleanup: "+snapshot.numChildren()+" activities");
var updates = {};
snapshot.forEach((child) => {
updates["activities/"+child.key] = null;
});
admin.database().ref().update(updates).then(() => {
res.status(200).send(snapshot.numChildren()+" activities deleted");
}).catch((error) => {
res.status(500).send(error);
})
});
});
了解详情:
- Firebase documentation on querying
- Firebase blog post on multi-location updates
这篇关于如何使用Firebase Cloud功能在DataSnapshot中查找特定值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
