Firebase 查询未按正确顺序执行?
Firebase query not executing in the correct order?
我获取数据并在 tableView 中显示,问题是数据未按正确顺序执行。
我试过:
for case let child as DataSnapshot in data!.children.reversed() {
let newDispatchGroup = DispatchGroup()
let commentID = child.key
let uid = child.childSnapshot(forPath: "UID").value as! String
let commentText = child.childSnapshot(forPath: "Comment").value!
let timeStamp = child.childSnapshot(forPath: "timeStamp").value!
let date = ConvertDate(mediaTimestamp: timeStamp as! Double).getDate!
//print(date, "dsfsdafdasfdsafdsahjkfhfdsafsajkadhffdsfsafsasjkfhsdajkhfdsajkhfjklads")
newDispatchGroup.enter()
ref.child("users2").child(uid).observeSingleEvent(of: .value, with: { (snapshot) in
print(snapshot, "dshjkfhjkadhfsjkfhsdajkhfdsajkhfjklads")
print(date, "dsfsdafdasfdsafdsahjkfhfdsafsajkadhffdsfsafsasjkfhsdajkhfdsajkhfjklads")
let username = snapshot.childSnapshot(forPath: "username").value
let profileImage = snapshot.childSnapshot(forPath: "profileImage").value
let newUser = User(theuserID: uid, theUsername: username as! String, theprofImage: profileImage as! String)
let newComment = Comment(newUser: newUser, text: commentText as! String, timeStamp: date, NcommentID: commentID)
self.commentsVC1.arrayOfComments.append(newComment)
newDispatchGroup.leave()
//completion()
})
newDispatchGroup.notify(queue: .main, execute: {
print(self.totalComments, "COgfdsdfgfdsgdsfgdfsgfdsgdfsgdskj", self.commentsVC1.arrayOfComments.count)
if self.totalComments == self.commentsVC1.arrayOfComments.count {
print("COmejkfbdshkafdsagfhksdagfdsakj")
self.commentsVC1.tableView.reloadData()
}
})
}
})
}
但是也没用,第二个firebase调用执行的顺序不对。
您应该在设置 DispatchGroup
时设置 notify
闭包。而且您不需要为 loadComments
函数使用完成闭包。
let dispatchGroup = DispatchGroup()
dispatchGroup.notify(queue: .main, execute: {
if self.totalComments == self.commentsVC1.arrayOfComments.count {
print("COmejkfbdshkafdsagfhksdagfdsakj")
self.commentsVC1.tableView.reloadData()
}
})
loadComments()
notify
将被调用,当 leave
被调用的次数与 enter
相同时。在您的代码中,最后一次 leave
调用发生在您设置要通知的任何内容之前。
我用这个解决了:
for case let child as DataSnapshot in snap.children.reversed() {
let commentID = child.key
let uid = child.childSnapshot(forPath: "UID").value as! String
let commentText = child.childSnapshot(forPath: "Comment").value!
let timeStamp = child.childSnapshot(forPath: "timeStamp").value!
let date = ConvertDate(mediaTimestamp: timeStamp as! Double).getDate!
let newUser = User(theuserID: uid)
let newComment = Comment(newUser: newUser, text: commentText as! String, timeStamp: date, NcommentID: commentID)
self.commentsVC1.arrayOfComments.append(newComment)
ref.child("users2").child(uid).observeSingleEvent(of: .value, with: { (snapshot) in
let username = snapshot.childSnapshot(forPath: "username").value
let profileImage = snapshot.childSnapshot(forPath: "profileImage").value
let newUserIner = User(theuserID: uid, theUsername: username as! String, theprofImage: profileImage as! String)
newComment.user = newUserIner
if self.totalComments == self.commentsVC1.arrayOfComments.count {
self.commentsVC1.tableView.reloadData()
}
})
}
我会在这里使用调度组,这样就不必检查它是否做了不必要的工作。
我获取数据并在 tableView 中显示,问题是数据未按正确顺序执行。
我试过:
for case let child as DataSnapshot in data!.children.reversed() {
let newDispatchGroup = DispatchGroup()
let commentID = child.key
let uid = child.childSnapshot(forPath: "UID").value as! String
let commentText = child.childSnapshot(forPath: "Comment").value!
let timeStamp = child.childSnapshot(forPath: "timeStamp").value!
let date = ConvertDate(mediaTimestamp: timeStamp as! Double).getDate!
//print(date, "dsfsdafdasfdsafdsahjkfhfdsafsajkadhffdsfsafsasjkfhsdajkhfdsajkhfjklads")
newDispatchGroup.enter()
ref.child("users2").child(uid).observeSingleEvent(of: .value, with: { (snapshot) in
print(snapshot, "dshjkfhjkadhfsjkfhsdajkhfdsajkhfjklads")
print(date, "dsfsdafdasfdsafdsahjkfhfdsafsajkadhffdsfsafsasjkfhsdajkhfdsajkhfjklads")
let username = snapshot.childSnapshot(forPath: "username").value
let profileImage = snapshot.childSnapshot(forPath: "profileImage").value
let newUser = User(theuserID: uid, theUsername: username as! String, theprofImage: profileImage as! String)
let newComment = Comment(newUser: newUser, text: commentText as! String, timeStamp: date, NcommentID: commentID)
self.commentsVC1.arrayOfComments.append(newComment)
newDispatchGroup.leave()
//completion()
})
newDispatchGroup.notify(queue: .main, execute: {
print(self.totalComments, "COgfdsdfgfdsgdsfgdfsgfdsgdfsgdskj", self.commentsVC1.arrayOfComments.count)
if self.totalComments == self.commentsVC1.arrayOfComments.count {
print("COmejkfbdshkafdsagfhksdagfdsakj")
self.commentsVC1.tableView.reloadData()
}
})
}
})
}
但是也没用,第二个firebase调用执行的顺序不对。
您应该在设置 DispatchGroup
时设置 notify
闭包。而且您不需要为 loadComments
函数使用完成闭包。
let dispatchGroup = DispatchGroup()
dispatchGroup.notify(queue: .main, execute: {
if self.totalComments == self.commentsVC1.arrayOfComments.count {
print("COmejkfbdshkafdsagfhksdagfdsakj")
self.commentsVC1.tableView.reloadData()
}
})
loadComments()
notify
将被调用,当 leave
被调用的次数与 enter
相同时。在您的代码中,最后一次 leave
调用发生在您设置要通知的任何内容之前。
我用这个解决了:
for case let child as DataSnapshot in snap.children.reversed() {
let commentID = child.key
let uid = child.childSnapshot(forPath: "UID").value as! String
let commentText = child.childSnapshot(forPath: "Comment").value!
let timeStamp = child.childSnapshot(forPath: "timeStamp").value!
let date = ConvertDate(mediaTimestamp: timeStamp as! Double).getDate!
let newUser = User(theuserID: uid)
let newComment = Comment(newUser: newUser, text: commentText as! String, timeStamp: date, NcommentID: commentID)
self.commentsVC1.arrayOfComments.append(newComment)
ref.child("users2").child(uid).observeSingleEvent(of: .value, with: { (snapshot) in
let username = snapshot.childSnapshot(forPath: "username").value
let profileImage = snapshot.childSnapshot(forPath: "profileImage").value
let newUserIner = User(theuserID: uid, theUsername: username as! String, theprofImage: profileImage as! String)
newComment.user = newUserIner
if self.totalComments == self.commentsVC1.arrayOfComments.count {
self.commentsVC1.tableView.reloadData()
}
})
}
我会在这里使用调度组,这样就不必检查它是否做了不必要的工作。