ios - 为什么我下载到同一个路径时得到不同的图像？

Question

我正在尝试调试一段用于上传图片和从我自己的服务器下载该图片的代码。

图片路径为“http://localhost/Twitter/Avatar/52/avatar.jpeg”

如我们所见，该文件夹中有两张图像，图像相同但名称不同。当我在下载图片时对路径进行硬编码时，我得到了一个奇怪的结果

 if avatarPath != nil {

        let x = "http://localhost/Twitter/Avatar/52/avatar.jpeg"

        let imageURL = URL(string: x)
        let session = URLSession(configuration: .default)
        let task = session.dataTask(with: imageURL!, completionHandler: { (data, response, error) in

            DispatchQueue.main.async {

                if let imageData = data {
                    self.avatarImage.image = UIImage(data: imageData)
                }
            }

        })

        task.resume()
    }



    // round courner of avatar
    avatarImage.layer.cornerRadius = avatarImage.bounds.width/20
    avatarImage.clipsToBounds = true

    //Give title to navigation controller
    self.navigationItem.title = username.uppercased()



    activityIndicator.stopAnimating()



}

当我写 let x = "http://localhost/Twitter/Avatar/52/pogba.jpeg "

我走和路径一样的图片，像这样

但是当我改成 let x = "http://localhost/Twitter/Avatar/52/avatar.jpeg "

我得到了不同的图像，像这样

我第一次上传图片的时候确实用过那个图片，但不知道为什么又出现了那个图片。我还没有实现缓存图像。为什么会这样？

这里是完整的源代码

import UIKit

class HomepageVC: UIViewController, UINavigationControllerDelegate, UIImagePickerControllerDelegate {


@IBOutlet weak var avatarImage: UIImageView!
@IBOutlet weak var usernameLabel: UILabel!
@IBOutlet weak var fullnameLabel: UILabel!
@IBOutlet weak var emailLabel: UILabel!
@IBOutlet weak var editAvatarButton: UIButton!
@IBOutlet weak var activityIndicator: UIActivityIndicatorView!



override func viewDidLoad() {
    super.viewDidLoad()

    activityIndicator.startAnimating()

    // mendeklarasikan variable user yang berasal dari superglobal variable di appdelegate
    let username = userInfo?["username"] as! String
    let fullname = userInfo?["fullname"] as! String
    let email = userInfo?["email"] as! String
    let avatarPath = userInfo?["avatar"] as? String


    // update user interface text & Label
    usernameLabel.text = username.uppercased()
    fullnameLabel.text = fullname.capitalized
    emailLabel.text = email



    // update user interface avatar

    if avatarPath != nil {

        let x = "http://localhost/Twitter/Avatar/52/pogba.jpeg"

        let imageURL = URL(string: x)
        let session = URLSession(configuration: .default)
        let task = session.dataTask(with: imageURL!, completionHandler: { (data, response, error) in

            DispatchQueue.main.async {

                if let imageData = data {
                    self.avatarImage.image = UIImage(data: imageData)
                }
            }

        })

        task.resume()
    }



    // round courner of avatar
    avatarImage.layer.cornerRadius = avatarImage.bounds.width/20
    avatarImage.clipsToBounds = true

    //Give title to navigation controller
    self.navigationItem.title = username.uppercased()



    activityIndicator.stopAnimating()



}





@IBAction func logoutButtonDidPressed(_ sender: Any) {

    //menghapus data userDefault yang sudah ada
    UserDefaults.standard.removeObject(forKey: "parsedJSON")
    UserDefaults.standard.synchronize()

    //menuju ke login page dengan modal segue
    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    let loginVC = storyboard.instantiateViewController(withIdentifier: "loginVC")
    present(loginVC, animated: true, completion: nil)

}



@IBAction func editProfilePictureButtonDidPressed(_ sender: Any) {

    // user akan memilih photo dari library atau dari camera nya


    let imagePickerController = UIImagePickerController()
    imagePickerController.delegate = self
    imagePickerController.allowsEditing = true



    let actionSheet = UIAlertController(title: "Photo Source", message: "please choose your source", preferredStyle: .actionSheet)


    // action camera
    let actionCamera = UIAlertAction(title: "Camera", style: .default) { (action) in

        if UIImagePickerController.isSourceTypeAvailable(.camera) {
            imagePickerController.sourceType = .camera
            self.present(imagePickerController, animated: true, completion: nil)

        } else {
            self.showAlert(alertTitle: "Opppss", alertMessage: "camera can't be used / not available", actionTitle: "OK")
            print("camera can't be used / not available")
        }

    }


    // action photo library
    let actionPhotoLibrary = UIAlertAction(title: "Photo Library", style: .default) { (action) in
        imagePickerController.sourceType = .photoLibrary
        self.present(imagePickerController, animated: true, completion: nil)
    }


    //action cancel
    let actionCancel = UIAlertAction(title: "Cancel", style: .cancel, handler: nil)


    actionSheet.addAction(actionCamera)
    actionSheet.addAction(actionPhotoLibrary)
    actionSheet.addAction(actionCancel)


    self.present(actionSheet, animated: true, completion: nil)



}






func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {


    let image = info[UIImagePickerControllerOriginalImage] as! UIImage
    avatarImage.image = image
    picker.dismiss(animated: true, completion: nil)



    // call func of uploading file to server
    uploadAvatar()

}




func imagePickerControllerDidCancel(_ picker: UIImagePickerController) {
    picker.dismiss(animated: true, completion: nil)
}






// custom HTTP request body to upload image file
func createBodyWithParams(_ parameters: [String: String]?, filePathKey: String?, imageDataKey: Data, boundary: String) -> Data {

    var body = Data();

    if parameters != nil {
        for (key, value) in parameters! {
            body.appendString("--\(boundary)\r\n")
            body.appendString("Content-Disposition: form-data; name=\"\(key)\"\r\n\r\n")
            body.appendString("\(value)\r\n")
        }
    }

    // kita set agar image yang di upload kemudian berformat .jpg
    let filename = "avatar.jpeg"

    let mimetype = "image/jpeg"

    body.appendString("--\(boundary)\r\n")
    body.appendString("Content-Disposition: form-data; name=\"\(filePathKey!)\"; filename=\"\(filename)\"\r\n")
    body.appendString("Content-Type: \(mimetype)\r\n\r\n")
    body.append(imageDataKey)
    body.appendString("\r\n")

    body.appendString("--\(boundary)--\r\n")

    return body as Data

}


// uploading image ke server
func uploadAvatar() {



    // mendapatkan ID dari User Default variable
    let id = userInfo!["id"] as! String


    // membuat request
    let url = URL(string: "http://localhost/Twitter/uploadAvatar.php")!
    var request = URLRequest(url: url)
    request.httpMethod = "POST"


    // parameter yang akan dikirim di dalam request body
    // parameter ini dibutuhkan karena uploadAvatar.php membutuhkan inputan ID
    let param = ["id" : id]

    // membuat Boundary
    let boundary = "Boundary-\(UUID().uuidString)"
    request.setValue("multipart/form-data; boundary=\(boundary)", forHTTPHeaderField: "Content-Type")


    // mengassign image yang akan di upload dan melakukan kompresi
    let imageData = UIImageJPEGRepresentation(avatarImage.image!, 0.5)

    // if not compressed, return ... do not continue to code
    if imageData == nil {
        return
    }





    // constructing http body
    request.httpBody = createBodyWithParams(param, filePathKey: "file", imageDataKey: imageData!, boundary: boundary)

    // filePathKey berupa 'file' agar nanti di PHP $_FILES bisa didentifikasi, contohnya $_FILES['file'][tmp_name]


    // launc session
    URLSession.shared.dataTask(with: request) { data, response, error in




        DispatchQueue.main.async(execute: {

            if error == nil {

                // maka tampilkan $returnArray dari PHP (response message from server)

                do {

                    // json containes $returnArray from php
                    let json = try JSONSerialization.jsonObject(with: data!, options: []) as? NSDictionary

                    // declare new parseJSON to store json
                    guard let parsedJSON = json else {
                        print("Error while parsing")
                        return
                    }


                    print(parsedJSON)

                    // get id from $returnArray["id"] in PHP - parseJSON["id"]
                    let id = parsedJSON["id"]

                    // successfully uploaded
                    if id != nil {

                        // save user information yang berasal dari server
                        UserDefaults.standard.set(parsedJSON, forKey: "parsedJSON")
                        userInfo = UserDefaults.standard.object(forKey: "parsedJSON") as? NSDictionary





                        // jika tidak ada "id" kiriman dari server, maka ada error message
                    } else {

                        // get main queue to communicate back to user
                        DispatchQueue.main.async(execute: {
                            let message = parsedJSON["message"] as! String
                            self.showAlert(alertTitle: "opppps", alertMessage: message, actionTitle: "OK")
                        })

                    }



                    // error ketika melakukan JSON serialization
                } catch {

                    // get main queue to communicate back to user
                    DispatchQueue.main.async(execute: {
                        let message = error.localizedDescription
                        self.showAlert(alertTitle: "SorryBroooo", alertMessage: message, actionTitle: "OK")
                    })

                }

                // error ketika koneksi ke server
            } else {

                // get main queue to communicate back to user
                DispatchQueue.main.async(execute: {
                    let message = error!.localizedDescription
                    self.showAlert(alertTitle: "oppps", alertMessage: message, actionTitle: "OK")
                })

            }


        })

        }.resume()


}






}







    // extend data
    extension Data {

        mutating func appendString(_ string : String) {

            let data = string.data(using: String.Encoding.utf8, allowLossyConversion: true)
            append(data!)

        }

    }

Answer 1

当您使用此代码时

let session = URLSession(configuration: .default)

您已自动注册默认缓存策略，它使用此链接中指定的基于永久磁盘的缓存: https://developer.apple.com/documentation/foundation/urlsessionconfiguration/1411560-default

如果你想删除所有缓存策略，请改用此代码

let session = URLSession(configuration: .ephemeral)