我设置了一个 onWrite 云函数来监听用户更新内容的时间。如果有超过 3 个,我正在尝试删除最老的 child ,这是我在:
exports.removeOld = functions.database.ref('/users/{uid}/media').onWrite(event => {
const uid = event.params.uid
if(event.data.numChildren() > 3) {
//Remove Oldest child...
}
})
这些 child 中的每一个都有一个“timestamp”
键。
{
"users" : {
"jKAWX7v9dSOsJtatyHHXPQ3MO193" : {
"media" : {
"-Kq2_NvqCXCg_ogVRvA" : {
"date" : 1.501151203274347E9,
"title" : "Something..."
},
"-Kq2_V3t_kws3vlAt6B" : {
"date" : 1.501151232526373E9,
"title" : "Hello World.."
}
"-Kq2_V3t_kws3B6B" : {
"date" : 1.501151232526373E9,
"title" : "Hello World.."
}
}
}
}
}
所以在上面的例子中,当文本值被添加到“media”时,最早的将被删除。
最佳答案
你需要这样的东西:
const MAX_LOG_COUNT = 3;
exports.removeOld = functions.database.ref('/users/{uid}/media/{mediaId}').onCreate(event => {
const parentRef = event.data.ref.parent;
return parentRef.once('value').then(snapshot => {
if (snapshot.numChildren() >= MAX_LOG_COUNT) {
let childCount = 0;
const updates = {};
snapshot.forEach(function(child) {
if (++childCount <= snapshot.numChildren() - MAX_LOG_COUNT) {
updates[child.key] = null;
}
});
// Update the parent. This effectively removes the extra children.
return parentRef.update(updates);
}
});
});
关于javascript - Cloud Functions for Firebase - 删除最老的 child ,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/45347426/