我在 Firebase 中最不喜欢的部分有问题。我想从用户的关注列表中提取一个帖子（每个用户只有一个帖子）。首先，我创建了一个完成处理程序来从 Firebase 获取所有关注者的列表并将其存储在 userArray 字符串数组中：
func GetUsersInFollowing(completion: @escaping (Bool) -> ()) {
ref.child("following").queryOrdered(byChild: FIRAuth.auth()!.currentUser!.uid).observeSingleEvent(of: .value, with: { (snapshot) in
for group in snapshot.children {
self.userArray.append((group as AnyObject).key)
}
completion(true)
})
}
现在的计划是从 userArray 的每个元素中提取一个帖子。这就是问题开始的地方。我在 GetUsersInFollowing() 完成后立即调用 CreatePosts()。
func CreatePosts() {
for x in userArray {
var thePost = Post()
print("1")
self.ref.child("users").child(x).observeSingleEvent(of: .value, with: { (snapshot) in
let value = snapshot.value as? NSDictionary
thePost.fullName = value?["fullname"] as? String ?? ""
thePost.username = value?["username"] as? String ?? ""
thePost.profileImageURL = value?["photourl"] as? String ?? ""
print("2")
})
self.ref.child("posts").child(x).observeSingleEvent(of: .value, with: { (snapshot) in
let value = snapshot.value as? NSDictionary
thePost.description = value?["description"] as? String ?? ""
thePost.info = value?["location"] as? String ?? ""
thePost.postImageURL = value?["photoURL"] as? String ?? ""
thePost.timePost = value?["timestamp"] as? NSDate
thePost.upVotes = value?["upvotes"] as? Int ?? 0
})
self.postArray.append(thePost)
self.tableView.reloadData()
}
}
对我来说一切都很好，但肯定不是。这是我创建单元格的方法：
func configureCell(post: Post) {
self.post = post
self.username.text = post.username
self.profileImage = post.profileImageURL
print("3")
self.fullname.text = post.fullName
self.timestamp.text = post.timePost
self.upvotes.text = post.upVotes
self.location.text = post.location
self.descriptionText.text = post.description
}
控制台中的输出各不相同，但通常我得到：1 1 3 3 2 2
这个想法是首先从 Firebase 检索所有数据，将其添加到 post 对象，将对象附加到数组，然后为该对象创建单元格并下载数据。即使未检索数据，单元格也已创建。我认为这就是问题所在。谢谢，每一个建议都值得赞赏。
您需要对用户个人资料数据和帖子数据进行内部查询。像这样 -
func CreatePosts() {
//Using userPostArrayObjFetched as a counter to check the number of data fetched.
//Remove this code, if you don't want to wait till all the user data is fetched.
var userPostArrayObjFetched = 0
for (index,userID) in userArray.enumerated() {
print("1" + userID)
self.ref.child("users").child(userID).observeSingleEvent(of: .value, with: { (snapshot) in
var thePost = Post()
let value = snapshot.value as? NSDictionary
thePost.fullName = value?["fullname"] as? String ?? ""
thePost.username = value?["username"] as? String ?? ""
thePost.profileImageURL = value?["photourl"] as? String ?? ""
print("2" + userID)
self.ref.child("posts").child(userID).observeSingleEvent(of: .value, with: { (snapshot) in
let value = snapshot.value as? NSDictionary
thePost.description = value?["description"] as? String ?? ""
thePost.info = value?["location"] as? String ?? ""
thePost.postImageURL = value?["photoURL"] as? String ?? ""
thePost.timePost = value?["timestamp"] as? NSDate
thePost.upVotes = value?["upvotes"] as? Int ?? 0
print("3" + userID)
self.postArray.append(thePost)
// Uncomment if you want to reload data as fetched from Firebase without waiting for all the data to be fetched.
// self.tableView.reloadData()
userPostArrayObjFetched += 1
if userPostArrayObjFetched == userArray.count{
self.tableView.reloadData()
}
})
})
}
}
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我来说两句