Ios 阵列更改时SwiftUI列表不更新
当每个列表元素出现时,它会检查它是否是数组中的最后一个元素。如果是,它将从Firestore获取更多信息并更新Ios 阵列更改时SwiftUI列表不更新,ios,swift,firebase,swiftui,swift4,Ios,Swift,Firebase,Swiftui,Swift4,当每个列表元素出现时,它会检查它是否是数组中的最后一个元素。如果是,它将从Firestore获取更多信息并更新fetchedPosts。但是,当数组更新时,列表不会更新,因此不会显示新元素 这是ObserveObject,它发布数组 private func elementOnAppear(_ post: Post) { /* onAppear on the view is called when a view appears on screen. elementOnAppea
fetchedPosts
。但是,当数组更新时,列表不会更新,因此不会显示新元素
这是ObserveObject,它发布数组
private func elementOnAppear(_ post: Post) {
/* onAppear on the view is called when a view appears on screen.
elementOnAppear asks the view model if the element is the last one.
If so, we ask the view model to fetch new data. */
if self.postsData.isLastPostInList(post: post) {
self.postsData.fetchPosts(userInfo: self.userInfo)
}
}
有什么解决办法吗?有几件事
class SocialObservable: ObservableObject{
let db = Firestore.firestore()
let objectWillChange = ObservableObjectPublisher()
@Published var fetchedPosts = [Post]()
@Published var lastSnap : DocumentSnapshot?
@Published var reachedEnd = false
var currentListener: ListenerRegistration?
var newFetch = false {
willSet{
objectWillChange.send()
}
}
init(userInfo: UserData){
print(userInfo.uid)
fetchPosts(userInfo: userInfo)
}
func fetchPosts(userInfo: UserData){
var first: Query?
if lastSnap == nil || newFetch {
//not last snapshot, or just updated feed
if newFetch{
newFetch.toggle()
fetchedPosts = [] // clean up if new fetch
}
first = db.collection("posts")
.whereField("availability", arrayContains: userInfo.uid)
.order(by: "date", descending: true)
.limit(to: 1)
}
else {
first = db.collection("posts")
.whereField("availability", arrayContains: userInfo.uid)
.order(by: "date", descending: true)
.start(afterDocument: lastSnap!)
.limit(to: 1)
}
first?.getDocuments(completion: { (snapshot, error) in
guard let snapshot = snapshot else {
print("Error: \(error.debugDescription)")
return
}
let doc = snapshot.documents.map({postFromDB(obj: $0.data(), id: $0.documentID)})
doc.map({print($0.postID)})
// append to fetched posts
self.fetchedPosts = self.fetchedPosts + doc
print(self.fetchedPosts.count)
//prepare for the next fetch
guard let lastSnapshot = snapshot.documents.last else {
// the collection is empty. no data fetched
self.reachedEnd = true
return
}
// save last snapshot
self.lastSnap = lastSnapshot
})
}
func isLastPostInList(post: Post) -> Bool {
return post.postID == fetchedPosts.last?.postID
}
}
postsData
定义为:@ObservedObject让postsData:socialobserveble
?-它必须是一个@ObservedObject
,视图才能因更新而刷新。顺便说一句,如果您要更改@Published
属性,您不需要同时使用objectWillChange.send
Hmm我将其更改为@ObservedObject var postsData=SocialObservable(userInfo:UserData())
,但问题仍然是一样的。。。对于objectWillChange.send
,请确保我可以将其更改为@published属性-我只希望视图能够切换newFetch。
class SocialObservable: ObservableObject{
let db = Firestore.firestore()
let objectWillChange = ObservableObjectPublisher()
@Published var fetchedPosts = [Post]()
@Published var lastSnap : DocumentSnapshot?
@Published var reachedEnd = false
var currentListener: ListenerRegistration?
var newFetch = false {
willSet{
objectWillChange.send()
}
}
init(userInfo: UserData){
print(userInfo.uid)
fetchPosts(userInfo: userInfo)
}
func fetchPosts(userInfo: UserData){
var first: Query?
if lastSnap == nil || newFetch {
//not last snapshot, or just updated feed
if newFetch{
newFetch.toggle()
fetchedPosts = [] // clean up if new fetch
}
first = db.collection("posts")
.whereField("availability", arrayContains: userInfo.uid)
.order(by: "date", descending: true)
.limit(to: 1)
}
else {
first = db.collection("posts")
.whereField("availability", arrayContains: userInfo.uid)
.order(by: "date", descending: true)
.start(afterDocument: lastSnap!)
.limit(to: 1)
}
first?.getDocuments(completion: { (snapshot, error) in
guard let snapshot = snapshot else {
print("Error: \(error.debugDescription)")
return
}
let doc = snapshot.documents.map({postFromDB(obj: $0.data(), id: $0.documentID)})
doc.map({print($0.postID)})
// append to fetched posts
self.fetchedPosts = self.fetchedPosts + doc
print(self.fetchedPosts.count)
//prepare for the next fetch
guard let lastSnapshot = snapshot.documents.last else {
// the collection is empty. no data fetched
self.reachedEnd = true
return
}
// save last snapshot
self.lastSnap = lastSnapshot
})
}
func isLastPostInList(post: Post) -> Bool {
return post.postID == fetchedPosts.last?.postID
}
}
class SocialObservable: ObservableObject{
let db = Firestore.firestore()
// let objectWillChange = ObservableObjectPublisher() // << remove this
// ...
var newFetch = false {
willSet{
self.objectWillChange.send() // ObservableObject has default
}
}
// ...
doc.map({print($0.postID)})
// append to fetched posts
DispatchQueue.main.async {
self.fetchedPosts = self.fetchedPosts + doc
}
print(self.fetchedPosts.count)