更新数组swift 4
更新数组swift 4
提问于 2018-12-07 16:42:47
我正在尝试通过从firebase数据库下载图像来更新图像数组。但是由于某些原因，在函数内部更新数组后，在viewdidload函数中不会更新数组。我是xcode的新手。有什么想法吗？
var images:[UIImage] = []
override func viewDidLoad() {
super.viewDidLoad()
ref = Database.database().reference()
retrieveImage()
print(self.images)
}
func retrieveImage(){
let userID = Auth.auth().currentUser?.uid
ref.child("Images").observeSingleEvent(of: .value, with: { (snapshot) in
let userImage = snapshot.value as? NSDictionary
let imageURLArray = userImage?.allKeys
if userImage != nil{
for index in 0...userImage!.count-1{
let imageProfile = userImage![imageURLArray?[index]] as? NSDictionary
let imageURL = imageProfile!["url"]
let storageRef = Storage.storage().reference(forURL: imageURL as! String)
storageRef.getData(maxSize: 1 * 1024 * 1024) { data, error in
if let error = error {
print(error.localizedDescription)
} else {
let image = UIImage(data: data!)
self.images.append(image!)
}
}
}
}
}) { (error) in
print(error.localizedDescription)
}
}回答 2
Stack Overflow用户
发布于 2018-12-07 16:55:07
因为observeSingleEvent是异步运行的，所以在observeSingleEvent结束之前调用打印函数。你可以像这样修复它，使用闭包
var images:[UIImage] = []
override func viewDidLoad() {
super.viewDidLoad()
ref = Database.database().reference()
retrieveImage {
print(self.images)
}
}
func retrieveImage(_ completion: () -> Void){
let userID = Auth.auth().currentUser?.uid
ref.child("Images").observeSingleEvent(of: .value, with: { (snapshot) in
let userImage = snapshot.value as? NSDictionary
let imageURLArray = userImage?.allKeys
if userImage != nil{
for index in 0...userImage!.count-1{
let imageProfile = userImage![imageURLArray?[index]] as? NSDictionary
let imageURL = imageProfile!["url"]
let storageRef = Storage.storage().reference(forURL: imageURL as! String)
storageRef.getData(maxSize: 1 * 1024 * 1024) { data, error in
if let error = error {
print(error.localizedDescription)
} else {
let image = UIImage(data: data!)
self.images.append(image!)
}
}
}
}
completion()
}) { (error) in
print(error.localizedDescription)
completion()
}
}Stack Overflow用户
发布于 2018-12-07 18:43:02
您可以像这样使用
var images:[UIImage] = []
override func viewDidLoad() {
super.viewDidLoad()
ref = Database.database().reference()
retrieveImage {
print(self.images)
}
}
func retrieveImage(_ completion: () -> Void){
let userID = Auth.auth().currentUser?.uid
ref.child("Images").observeSingleEvent(of: .value, with: { (snapshot) in
let userImage = snapshot.value as? NSDictionary
let imageURLArray = userImage?.allKeys
if userImage != nil {
for index in 0...userImage!.count-1 {
let imageProfile = userImage![imageURLArray?[index]] as? NSDictionary
let imageURL = imageProfile!["url"]
let storageRef = Storage.storage().reference(forURL: imageURL as! String)
storageRef.getData(maxSize: 1 * 1024 * 1024) { data, error in
if let error = error {
completion()
print(error.localizedDescription)
} else {
let image = UIImage(data: data!)
self.images.append(image!)
if index == userImage!.count-1 {
completion()
}
}
}
}
} else {
completion()
}
}) { (error) in
print(error.localizedDescription)
completion()
}
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/53665970
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