下载图像，然后从 Firebase Swift 3 缓存它

Posted 2023-02-24

【中文标题】下载图像，然后从 Firebase Swift 3 缓存它

【英文标题】：Downloading Image, then Cache it from Firebase Swift 3

【发布时间】：2016-12-07 19:50:40

【问题描述】：

我目前正在尝试设置用户个人资料图片。我让用户拍摄了一张上传到 Firebase 的图片，但我想下载该图片并将其缓存。我现在下载它时遇到问题，修复后我会担心缓存它。

 // Uploading Images to Firebase
func uploadImageToFirebaseStorage(data: NSData ) 
    let storageRef = FIRStorage.storage().reference(withPath: "myPics/profilePic.jpg")
    let uploadMetaData = FIRStorageMetadata()
    uploadMetaData.contentType = "image/jpeg"
    let uploadTask = storageRef.put(data as Data, metadata: uploadMetaData)  (metadata, error) in
        if (error != nil) 
            print("I Received an error \(error?.localizedDescription)")
         else 
            print("Upload Complete! Here is the MetaData \(metadata?.downloadURL())")
        

    

现在问题导航器有什么问题：

reference = self.storage 上有这个问题。提前谢谢！

//Download Image for User Profile Picture
func downloadImageUserFromFirebase() 
    let storage = FIRStorage.storage()
    var reference: FIRStorageReference!
        reference = self.storage.referenceForURL("gs:URL.appspot.com")
        reference.downloadURL  (url, error) in
    let data = NSData(contentsOf: url!)
    let image = UIImage(data: data! as Data)
    self.profileImageView.image = image
    
    

【参考方案1】：

Storage 没有声明为类的属性，它是在该方法中声明的。此外，即使它被声明为类的属性，在 swift 中你不需要再将 self 放在类属性之前，除非你在闭包中。

要么做：

func downloadImageUserFromFirebase() 
  let storage = FIRStorage.storage()
  var reference: FIRStorageReference!
  //all I did here was remove self before storage
  reference = storage.referenceForURL("gs:URL.appspot.com")
  reference.downloadURL  (url, error) in
    let data = NSData(contentsOf: url!)
    let image = UIImage(data: data! as Data)
    self.profileImageView.image = image
  

或者，理想情况下，重构代码：

class ProfileViewController: UIViewController 

  //here we are initializing it as a property of the class
  let storage = FIRStorage.storage()

  func downloadImageUserFromFirebase() 
    var reference: FIRStorageReference = storage.referenceForURL("gs:URL.appspot.com")
    reference.downloadURL  (url, error) in
      //using a guard statement to unwrap the url and check for error
      guard let imageURL = url, error == nil 
        //handle error here if returned url is bad or there is error
        return
      
      guard let data = NSData(contentsOf: imageURL) else 
        //same thing here, handle failed data download
        return
      
      let image = UIImage(data: data)
      self.profileImageView.image = image
    
  

【参考方案2】：

reference.downloadurl 将识别当前用户的图片，或者我们应该将 profileimageurl 保存在数据库中