检索 Firebase 图片 - 图片视图

Question

大家好，我正在尝试从Firebase数据库中获取我的图片，并将其作为用户的个人资料图片呈现到图片视图中。我要做的第一件事是创建一个方法来检索数组中的照片数据

class PhotoService {

static func retrievePhotos(completion: @escaping ([Photo]) -> Void) {

//get a databas refrence
let db = Firestore.firestore()

//get data from "photos" collection
db.collection("photos").getDocuments { (snapshot, Error) in

//check for errors
if Error != nil {
//error in retrieving photos
return
}

//get all the documents
let documents = snapshot?.documents

//check that documents arent nil
if let documents = documents {

//create an array to hold all of our photo structs
var photoArray = [Photo]()

//loop through documents, get a photos struct for each
for doc in documents {

//create photo struct
let p = Photo(snapshot: doc)

if p != nil {

//store it in an array
photoArray.insert(p!, at: 0)

}

}

//pass back the photo array
completion(photoArray) 

}

}

}

然后我调用该类并尝试在图像视图中显示图像

@IBOutlet var profilePictureImageView: UIImageView!

var photos = [Photo]()

override func viewDidLoad() {
super.viewDidLoad()

//call the photo service to retrieve the photos
PhotoService.retrievePhotos { (retrievedPhotos) in

//set the photo array to the retrieved photos
self.photos = retrievedPhotos

//make the image view a circle
self.profilePictureImageView.layer.cornerRadius = self.profilePictureImageView.bounds.height / 2
self.profilePictureImageView.clipsToBounds = true

//make the image view display the photo
var photo:Photo?

func displayPhoto(photo:Photo) {

//check for errors
if photo.photourl == nil {
return
}

//download the image
let photourl = URL(string: photo.photourl!)

//check for erorrs
if photourl == nil {
return
}

//use url session to download the image asynchronously
let session = URLSession.shared

let dataTask = session.dataTask(with: photourl!) { (data, response, Error) in

//check for errors
if Error == nil && data != nil {

//let profilePictureImageView = UIImage()
let image = UIImage(data: data!)

//set the image view
DispatchQueue.main.async {
self.profilePictureImageView.image = image
}

}

}

dataTask.resume()  
}
}
}
}

我不明白我做错了什么以及为什么图像没有显示，如果有人可以向我解释这一点并给我一个令人惊叹的代码示例，解释它就好像你在向 5 年级的孩子解释它

一样

Answer 1

在以下步骤中，可以轻松完成从Firebase获取图像并将其分配给ImageView的快速方法。

获取PhotoUrl的功能

//Function to get photo of loggedin User
func getUrl(Completion:@escaping((String)->())) {
let userID = Auth.auth().currentuser?.uid
let db = Firestore.firestore().collection("photos").document(userID)
db.getDocument { (docSnapshot, error) in
if error != nil {
return
} else {
guard let snapshot = docSnapshot, snapshot.exists else {return}
guard let data = snapshot.data() else {return}
let imageUrl = data["photoUrl"] as! String
completion(imageUrl)

}
}
}

To download image and assign it to image view

//Call this function in VC where your `ImageView` is
func getImage(Url:String){
DispatchQueue.global().async {
let url = URL(string: Url)
if let data = try? Data(contentsOf: url!) {
DispatchQueue.main.async {
self.profilePictureImageView.image = UIImage(data: data)
}
}
}
}
}

在viewDidLoad中调用这些内容，如下所示：

getUrl{(url) in
getImage(Url:url)
}