我通过以下方式从Firebase获取数据：
fetchUsers (gets UIDs of people the current user follows)
-for each user fetch his posts
-for this user fetch his personal user-data (like profile image and username)
注意：我在调用"每个用户获取他的帖子">后重新加载数据，并在每个帖子中重新加载数据。
现在这是奇怪的部分。 在下面显示的方法(在查询 firebase 以获取必要数据时调用)中，有显示数据的打印语句。查看此数据时，它始终根据需要存在(个人资料图像URL以及用户名等。
func addUserDataToObject(userObj: User, snapshot: DataSnapshot) {
if (snapshot.childSnapshot(forPath: "username").value as! String) != "" {
userObj.profileImageUrlString = "(snapshot.childSnapshot(forPath: "profileImage").value as! String)"
userObj.fullName = "(snapshot.childSnapshot(forPath: "fullName").value as! String)"
userObj.username = "(snapshot.childSnapshot(forPath: "username").value as! String)"
print("(snapshot.childSnapshot(forPath: "profileImage").value as! String)", " this was wireed")
} else {
print("the username was nil!")
}
}
但是，当我尝试在 collectionView 方法中使用该数据时，它不存在： 我打印：
print(postArray[indexPath.item].user.username, " This is supposed to be the username")
print(postArray[indexPath.item].user.profileImageUrlString!, " This is supposed to be the URL")
print(date, " This is supposed to be the date")
所有这些都将"随机"打印空字符串。有时我应该注意到它们确实有效。我发现第一个单元格项目始终如一地工作正常，但其他 2 个则不然。
为什么会发生这种情况，我该如何解决？
更新：
下面是一些请求的代码：
func fetchAllUserFirstPostMedia(user: String) {
print("2344 fetch called 32424243242")
let databaseN = Database.database().reference()
databaseN.child("Posts").child(user).observe(.value, with: {(snapshot) in
guard snapshot.value as? [String: AnyObject] != nil else { return print("(snapshot.value) <-- this is snapshot.value in return statement") }
let userUID = user
if user == userUID {
guard let postDictionary = snapshot.value as? [String:AnyObject] else { return }
for anyPosts in postDictionary {
print("inside the anyPosts")//will print as many times as there are posts.
let currentPost = Post()
let userObj = User(theuserID: userUID)
self.retrieveUsersInfo(userObj: userObj)
print(userObj.profileImageUrlString, " This is teh uirl for prof image")//this is Always empty (even though at leaased the first value has an image dysplayed and all seem to ahve had one when in the retriveUsersInfo() method)
...
更新2：
我发现问题只发生在集合视图中的中间 2 个项目(这总是正确的：->索引 1 和 2 总是有问题，无论 n 是什么)(如果它有 4 个项目。项目越多会导致只有项目 1 和 2 有问题)
您的retrieveUsersInfo(userObj: User)方法是异步的，因此用于填充collectionView的数据可能不会及时加载。
尝试将retrieveUsersInfo方法重写为闭包，然后在找到用户信息后遍历 post 字典(我不知道你对循环遍历的anyPosts对象做了什么，但这是我所拥有的)：
func fetchAllUserFirstPostMedia(user: String) {
print("2344 fetch called 32424243242")
let ref = Database.database().reference()
ref.child("Posts/(user)").observe(.value, with: { snapshot in
guard let postDictionary = snapshot.value as? [String:AnyObject] else {
print("(snapshot.value) <-- this is snapshot.value in return statement")
return
}
let userObj = User(theuserID: user)
var posts = [Post]()
self.retrieveUsersInfo(userObj: userObj) {
print(userObj.profileImageUrlString)
for anyPosts in postDictionary {
print("inside the anyPosts")
let currentPost = Post()
// do whatever you need to do with anyPosts, currentPost, and userObj
// add post object to array
posts.append(currentPost)
}
print(posts) // all of your posts with the complete userObj
}
})
}
func retrieveUserInfo(userObj: User, completion: @escaping () -> Void) {
let ref = Database.database().reference()
// I'm assuming this UID object is the userObj's uid and it's coming from somewhere else?
ref.child("Users").child(UID).observe(.value, with: { snapshot in
self.addUserDataToObject(userObj: userObj, snapshot: snapshot)
completion()
})
}
我在您的fetchAllUserFirstPostMedia方法中更改了几件事：
- 您不需要两个保护语句来测试快照的值是否退出
- 您将常量
userUID设置为等于user，因此 if 语句if user == userUID将始终成功 - 在循环之前设置常量
userObj这样它就不会设置每个循环迭代。