问题
I enrolled a course on Udemy a while back, on how to create a chat application with Swift and Firebase, simply because I wanted to get an insight of how it all was working.
However, I finished the course a week later. This was a couple of months ago, and since then - there has been an update to both Firebase and Swift, and I am currently struggling with converting some of the old code, to new code.
Here is the code that I am currently struggling with:
func loadRecents() {
firebase.child("Recent").queryOrdered(byChild: "userId").queryEqual(toValue: FIRAuth.auth()!.currentUser?.uid).observe(.value) { (snapshot:FIRDataSnapshot) in
self.recents.removeAll()
if snapshot.exists() {
if let values = snapshot.value as? [String:AnyObject] {
let sorted = (values as! NSArray).sortedArray(using: [NSSortDescriptor(key: "date", ascending: false)])
for recent in sorted {
self.recents.append(recent as! NSDictionary)
self.conversationTableView.reloadData()
}
}
self.conversationTableView.reloadData()
}
self.conversationTableView.reloadData()
}
self.checkUnread()
}
So this is simply the code of displaying all the "Chats" in a tableView, where I am simply sorting it through Date, where ascending is false.
The changes that I have made, is simply to convert the old snapshot.value.allValues to snapshot.value as? [String:AnyObject]. The query is sorted by the logged in account (FIRAuth.auth().currentUser!.uid).
However, I am very sure this code is deprecated, as I get an error each time I build this. And I know for a fact that it worked in the previous version.
This is the error:
Thread 1: EXC_BAD_INSTRUCTION
And if it is necessary, and it happens that I have messed up the current code completely (which might be), here is the full old code:
func loadRecents() {
firebase.child("Recent").queryOrderedByChild("userId").queryEqualToValue(FIRAuth.auth()!.currentUser!.uid).observeEventType(.Value, withBlock: {
snapshot in
self.recents.removeAll()
if snapshot.exists() {
let sorted = (snapshot.value!.allValues as NSArray).sortedArrayUsingDescriptors([NSSortDescriptor(key: "date", ascending: false)])
for recent in sorted {
self.recents.append(recent as! NSDictionary)
//add functio to have offline access as well, this will download with user recent as well so that we will not create it again
firebase.child("Recent").queryOrderedByChild("chatRoomID").queryEqualToValue(recent["chatRoomID"]).observeEventType(.Value, withBlock: {
snapshot in
})
}
}
self.tableView.reloadData()
})
self.checkUnread()
}
Any ideas on how I would bypass/fix this? Help is greatly appreciated.
回答1:
You have to use Dictionary()
if let values = (snapshot.value) as! Dictionary
回答2:
I don't know the Firebase structure but here's a solution if the data looks like this:
[
("post_42", ["date": "2016-09-16"]),
("post_12", ["date": "2016-09-19"]),
("post_87", ["date": "2016-09-04"])
]
and some code to print the data sorted by the date (this would go inside the block/closure)
let dict = snapshot!.value as! [String:[String:String]]
//print the unordered data from the dictionary
for item in dict {
print(item)
}
let sortedArray = Array(dict).sorted { $0.1["date"]! < $1.1["date"]! }
//print the data sorted by date
for sortedItem in sortedArray {
print(sortedItem)
}
来源：https://stackoverflow.com/questions/39705363/swift-3-firebase-update-code-convertion-sorting