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照片。我有用户拍摄上传到Firebase的图片，但我想下载该图片并将其缓存。我现在正在下载它时遇到问题，在我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())")
        }

    }

现在我遇到了问题导航器的问题：

reference = self.storage上存在此问题。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
    }
    }

Answer 1

存储未被声明为类的属性，它是在该方法中声明的。此外，即使它被宣布为班级的财产，在swift中你也不需要将自己置于一个类属性之前，除非你在一个闭包之内。

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
    }
  }

}

Answer 2

reference.downloadurl将识别当前用户的图像，否则我们应该将profileimageurl保存在数据库中