ios - 下载图像，然后从 Firebase Swift 3 缓存它

Question

我目前正在尝试设置用户个人资料图片。我让用户拍了一张上传到 Firebase 的图片，但我想下载该图片并缓存它。我现在在下载它时遇到问题，在我解决这个问题后，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())")
        }

    }

现在我在使用 Issue Navigator 时遇到的问题:

它在 reference = self.storage 上有这个问题。提前致谢!

//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
    }
    }

Answer 1

存储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 中你也不需要再将 self 放在类属性之前，除非你在闭包中。

要么:

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
    }
  }

}