【发布时间】：2018-01-12 21:12:45
【问题描述】：
我已经把问题归结为这个
这个闭包：
override func viewDidLoad() {
super.viewDidLoad()
let data = homeDataSource()
getPrivatePosts { (posts) in
print("postsCOUNT" , posts!.count)
data.posts = posts!
}
self.datasource = data
collectionView?.reloadData()
}
打印出“postCOUNT 1 postCOUNT 3”
然后当我打印 data.posts 的计数时，我得到 0...这是怎么回事？这是完整的代码
这是一个自定义的 UICollectionView：
import LBTAComponents
import Firebase
class homeView: DatasourceController {
override func viewDidLoad() {
super.viewDidLoad()
let data = homeDataSource()
getPrivatePosts { (posts) in
print("postsCOUNT" , posts!.count)
data.posts = posts!
}
self.datasource = data
collectionView?.reloadData()
}
override func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: view.frame.width , height: 150)
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForHeaderInSection section: Int) -> CGSize {
return CGSize(width: view.frame.width, height: 0 )
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForFooterInSection section: Int) -> CGSize {
return CGSize(width: view.frame.width, height: 0)
}
// just to test
override func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
performSegue(withIdentifier: "goToNewPost", sender: self)
}
func getPrivatePosts(completion : @escaping (_ privatePosts : [Post]?) ->()){
// fill posts array with posts from all buddys "privataPosts only"
var ret = [Post]()
staticValuesForData.instance.dataBaseUserref.child((Auth.auth().currentUser?.uid)!).child("contacts").observe( .value , with: { (snapshot) in
let dict = snapshot.children.allObjects as! [DataSnapshot]
for d in dict{
if let contactUid = d.childSnapshot(forPath: "uid").value as? String{
staticValuesForData.instance.dataBaseUserref.child(contactUid).child("privatePosts").observe( .value, with: { (snapshot) in
let posts = snapshot.children.allObjects as! [DataSnapshot]
print("postval" , posts)
for post in posts{
if let dict = post.value as? [String : AnyObject]{
let fullname = dict["fullname"] as! String
let picUrl = dict["picUrl"] as! String
let postContent = dict["postContent"] as! String
let time = dict["time"] as! Int
let uid = dict["uid"] as! String
let username = dict["username"] as! String
print("first name of person who did the post" , fullname)
let reposts = dict["reposts"] as! [String]
let downs = dict["downs"] as! [String]
// possible issue
var comments = [Comment]()
let commentArr = snapshot.childSnapshot(forPath: "comments").children.allObjects as! [DataSnapshot]
for c in commentArr{
if let dict = c.value as? [String : AnyObject]{
let cuid = dict["uid"] as! String
let ccommentText = dict["commentText"] as! String
let cpicUrl = dict["picUrl"] as! String
let cusername = dict["username"] as! String
let ctime = dict["time"] as! Int
let com = Comment(uid: cuid, commentText: ccommentText, time: ctime, picUrl: cpicUrl, username: cusername)
comments.append(com)
}
}
print("HERE : post content\(postContent) username : \(username) commentArr \(comments)")
let postToAdd = Post(postContent: postContent, picUrl: picUrl, userName: username, fullName: fullname, postID: uid, postTime: time, downs: downs, reposts: reposts, comments: comments)
print("LOOK AT MEE \(postToAdd.userName) is the username of the post object \(postToAdd.postContent) is the contetn")
ret.append(postToAdd)
print("RET" , ret)
}
}
completion(ret) // this is where the completion block should be called
})
}
}
})
}
}
这是一个数据源对象：
import LBTAComponents
class homeDataSource: Datasource {
var posts = [Post]()
override func numberOfItems(_ section: Int) -> Int {
print("COUNT " , posts.count)
return posts.count
}
override func headerClasses() -> [DatasourceCell.Type]? {
return [userHeader.self]
}
override func footerClasses() -> [DatasourceCell.Type]? {
return [userFooter.self]
}
override func cellClasses() -> [DatasourceCell.Type] {
return [userCell.self]
}
override func item(_ indexPath: IndexPath) -> Any? {
return posts[indexPath.item]
}
}
框架可以在这里使用：
pod 'LBTAComponents'
【问题讨论】：
-
您能否发布 Firebase 数据结构的屏幕截图？
-
绝对不可能在包含异步任务的闭包中声明一个具有默认值的变量。无论如何，从包含异步任务的函数中返回某些东西是不可能的。请学习了解异步数据处理的工作原理。
-
@rMickeyD 问题与数据库无关。我知道我的“ret”帖子数组中有正确的对象问题在于为什么“帖子”数组没有被填充，谢谢你的帮助
-
你能给我解释一下吗？ @vadian
-
您必须在异步代码块内调用完成，否则它会在异步完成之前调用完成行并且永远不会更新。
标签： ios swift asynchronous