介紹
你好呀。我最近問了一個不同的問題，詢問如何實作用戶觸發的 FCM。我很快意識到，為了實作 FCM，我需要在我的應用程式中添加另一個功能，這就是我現在在這里的原因。我在努力，相信我。
我的問題/問題
在我附上的圖片中，您可以看到當用戶單擊朋友選項卡時應該顯示的文本。但它不會那樣做。當我重繪 串列時它會這樣做，因為我將函式放在可重繪 屬性中。我也確實將該函式放在了視圖初始化中，但它并沒有做我想要它做的事情。所以我的問題是，a）為什么它不加載？b）解決我的問題的方法是什么？
代碼參考
此函式在視圖的 init{} 和視圖.refreshable{}內的串列中呼叫。（我也嘗試通過.onAppear{}在父視圖的 NavigationLink 中添加它。）
@State var bestfriend: String = ""
func getBestie() {
let db = Firestore.firestore()
let docRef = db.collection("users").document(email)
docRef.getDocument { (document, error) in
if let document = document, document.exists {
let bestie = document.get("bestie") as? String ?? "error: bestie"
bestfriend = String(bestie)
} else {
print("Document does not exist")
}
}
}
圖片供參考
感謝和注釋
非常感謝您，我每天都為這個社區的神奇程度以及這么多人愿意提供幫助而感到驚訝。如果您需要我添加任何其他內容，我當然會這樣做。我希望有一天我能足夠聰明地幫助其他人解決他們的問題。
編輯
風景
import Firebase
import FirebaseAuth
import SDWebImage
import SDWebImageSwiftUI
import SwiftUI
struct View_Friend_Tab: View {
@ObservedObject var friends_model = Model_User()
@State var friendWho = ""
init() {
friends_model.getFriendlist()
//friends_model.getBestie()
getBestie()
}
//VARS
let gifurl = URL(string: "https://c.tenor.com/BTCEb08QgBgAAAAC/osita-iheme-aki-and-pawpaw.gif")
let avatarURL = URL(
string:
"https://firebasestorage.googleapis.com/v0/b/universerp-72af2.appspot.com/o/avatars/anime-girl-white-hair-1-cropped.jpg?alt=media&token=efba4215-850d-41c8-8c90-385f7a572e94"
)
@State var showingAlert = false
@State var showFriendRequests = false
@State var bestfriend: String = ""
func getBestie() {
let db = Firestore.firestore()
let docRef = db.collection("users").document(email)
docRef.getDocument { (document, error) in
if let document = document, document.exists {
let bestie = document.get("bestie") as? String ?? "error: bestie"
bestfriend = String(bestie)
} else {
print("Document does not exist")
}
}
}
var body: some View {
if !showFriendRequests {
VStack {
NavigationView {
/*
List (friends_model.friend_list) { item in
HStack {
Text(item.email)
Spacer()
}
}
.refreshable{
friends_model.getFriendlist()
}
.listStyle(.grouped)
*/
List {
Section(header: Text("management")) {
NavigationLink(destination: View_Friend_Best_Tab()) {
Label("Select your bestie", systemImage: "star.fill")
}
NavigationLink(destination: View_Friend_Requests_Tab()) {
Label("Manage friend requests", systemImage: "person.fill.questionmark")
}
NavigationLink(destination: View_Friend_Add_Tab()) {
Label("Add friend", systemImage: "person.fill.badge.plus")
}
}
ForEach(friends_model.friend_list) { item in
let avURL = URL(string: item.avatarURL)
Section(header: Text(item.username)) {
HStack {
VStack(alignment: .leading) {
if bestfriend == item.email {
Text("Is your Shin'yū")
.foregroundColor(Color("lightRed"))
.fontWeight(.bold)
.font(.footnote)
}
Text(item.username)
.fontWeight(.bold)
.frame(alignment: .leading)
Text(item.email)
.font(.footnote)
.multilineTextAlignment(.leading)
}
Spacer()
WebImage(url: avURL)
.resizable(resizingMode: .stretch)
.aspectRatio(contentMode: .fit)
.frame(width: 50, height: 50)
.clipShape(Circle())
.shadow(radius: 5)
.overlay(Circle().stroke(Color.black, lineWidth: 1))
}
Button("Remove", role: .destructive) {
showingAlert = true
}
.alert("Do you really want to remove this friend?", isPresented: $showingAlert) {
HStack {
Button("Cancel", role: .cancel) {}
Button("Remove", role: .destructive) {
friendWho = item.email
removeFriend()
withAnimation {
friends_model.getFriendlist()
}
}
}
}
}
}
}
.navigationTitle("Your Friends")
.navigationViewStyle(.automatic)
.refreshable {
friends_model.getFriendlist()
getBestie()
}
.listStyle(.insetGrouped)
Spacer()
}
}
} else {
View_Friend_Requests_Tab()
}
}
}
struct View_Friend_Tab_Previews: PreviewProvider {
static var previews: some View {
View_Friend_Tab()
}
}
如前所述，該函式在 init 塊中和串列重繪 時被呼叫。
uj5u.com熱心網友回復：
作為一般建議，使用視圖模型來保持視圖代碼干凈。
在 SwiftUI 中，視圖的初始化程式不應執行任何昂貴/長時間運行的計算。請記住，在 SwiftUI 中，視圖只是對 UI 的描述，而不是 UI 本身。任何狀態管理都應該在初始化程式之外處理。
在您的情況下，使用.onAppearor .task：
import Firebase
import FirebaseAuth
import SDWebImage
import SDWebImageSwiftUI
import SwiftUI
class FriendsViewModel: ObservableObject {
@Published var bestfriend: String = ""
func getBestie() {
let db = Firestore.firestore()
let docRef = db.collection("users").document(email)
docRef.getDocument { (document, error) in
if let document = document, document.exists {
// consider using Codable for mapping - see https://peterfriese.dev/posts/firestore-codable-the-comprehensive-guide/
let bestie = document.get("bestie") as? String ?? "error: bestie"
self.bestfriend = String(bestie)
} else {
print("Document does not exist")
}
}
}
// add other functions and properties here.
}
struct FriendsView: View {
@ObservedObject var viewModel = FriendsViewModel()
//VARS
let gifurl = URL(string: "https://c.tenor.com/BTCEb08QgBgAAAAC/osita-iheme-aki-and-pawpaw.gif")
let avatarURL = URL(
string:
"https://firebasestorage.googleapis.com/v0/b/universerp-72af2.appspot.com/o/avatars/anime-girl-white-hair-1-cropped.jpg?alt=media&token=efba4215-850d-41c8-8c90-385f7a572e94"
)
@State var showingAlert = false
@State var showFriendRequests = false
@State var bestfriend: String = ""
var body: some View {
if !showFriendRequests {
VStack {
NavigationView {
List {
Section(header: Text("management")) {
NavigationLink(destination: SelectBestieView()) {
Label("Select your bestie", systemImage: "star.fill")
}
NavigationLink(destination: ManageFriendRequestsView()) {
Label("Manage friend requests", systemImage: "person.fill.questionmark")
}
NavigationLink(destination: AddFriendsView()) {
Label("Add friend", systemImage: "person.fill.badge.plus")
}
}
ForEach(viewModel.friends) { friend in
let avURL = URL(string: friend.avatarURL)
Section(header: Text(friend.username)) {
HStack {
VStack(alignment: .leading) {
if bestfriend == friend.email {
Text("Is your Shin'yū")
.foregroundColor(Color("lightRed"))
.fontWeight(.bold)
.font(.footnote)
}
Text(friend.username)
.fontWeight(.bold)
.frame(alignment: .leading)
Text(friend.email)
.font(.footnote)
.multilineTextAlignment(.leading)
}
Spacer()
WebImage(url: avURL)
.resizable(resizingMode: .stretch)
.aspectRatio(contentMode: .fit)
.frame(width: 50, height: 50)
.clipShape(Circle())
.shadow(radius: 5)
.overlay(Circle().stroke(Color.black, lineWidth: 1))
}
Button("Remove", role: .destructive) {
showingAlert = true
}
.alert("Do you really want to remove this friend?", isPresented: $showingAlert) {
HStack {
Button("Cancel", role: .cancel) {}
Button("Remove", role: .destructive) {
friendWho = friend.email
viewModel.removeFriend()
withAnimation {
viewModel.getFriendlist()
}
}
}
}
}
}
}
.navigationTitle("Your Friends")
.navigationViewStyle(.automatic)
.onAppear {
viewModel.getFriendlist()
viewModelgetBestie()
}
.refreshable {
viewModel.getFriendlist()
viewModelgetBestie()
}
.listStyle(.insetGrouped)
Spacer()
}
}
} else {
FriendRequestsView()
}
}
}
struct FriendsViewPreviews: PreviewProvider {
static var previews: some View {
FriendsView()
}
}
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