SwiftUIImageViewFirebaseDispatchQueue

我正在使用 firebase 來保存和加載我的影像。我在 Xcode 中創建了一個新視圖，并使用與加載組態檔影像相同的代碼。然而，這現在拋出一個錯誤，說 url 字串為零。影像 url 資料在“DispatchQueue.global().async”后消失。什么可能導致這種情況，我該如何跟蹤？很奇怪這段代碼如何適用于其他視圖，但對于這個新視圖卻拋出錯誤。

let businessProfilePicture = dictionary["profPicString"] as! String
      if businessProfilePicture.count > 0 {
        let url = URL(string: businessProfilePicture)
        print(url)
        print("printing the url here to check")
        DispatchQueue.global().async {
          let dataURL = try? Data(contentsOf: url!)
          print(dataURL)
          print("printing the data url here")
          DispatchQueue.main.async {
            print(dataURL)
            print("Printing Data to check")
            let image = UIImage(data: dataURL!)?.potter_circleo
            self.businessProfilePicture.contentMode = UIView.ContentMode.scaleAspectFill
            self.businessProfilePicture.image = image
          }
        }

完整代碼

func getWorkLocation() {
    let uid = Auth.auth().currentUser?.uid
    var profPicURL: String = ""
    
    Database.database().reference().child("employees").child(uid!).child("Business").observe(.value, with: { snapshot in
        if snapshot.exists() {
            let dictionary = snapshot.value as? NSDictionary
                self.businessName.text = dictionary?["businessName"] as? String
                self.businessStreet.text = dictionary?["businessStreet"] as? String
                self.businessCity.text = dictionary?["businessCity"] as? String
                profPicURL = dictionary?["profPicString"] as! String
                
                // set image
                if profPicURL.count > 0 {
                    let url = URL(string: profPicURL)
                    DispatchQueue.global().async {
                        let data = try? Data(contentsOf: url!)
                        DispatchQueue.main.async {
                            let image = UIImage(data: data!)?.potter_circle
                            self.businessProfilePicture.contentMode = UIView.ContentMode.scaleAspectFill
                            self.businessProfilePicture.image = image
                        }
                    }
                } else {
                    let image = UIImage(named: "profile picture")?.potter_circle
                    self.businessProfilePicture.contentMode = UIView.ContentMode.scaleAspectFill
                    self.businessProfilePicture.image = image
                }
                 
        } else {
            self.businessName.text = ""
            self.businessStreet.text = "Go to Add Work Location to send request"
            self.businessCity.text = ""
            self.deleteButton.isEnabled = false
        }
    })
}

uj5u.com熱心網友回復：

您確定您創建的 URLprofPicURL是正確創建的嗎？

URL(string:)可以失敗并回傳nil。如果你繼續隱式地解包它，Data(contentsOf: url!)你會崩潰。

同樣，try? Data(contentsOf: url)可以回傳 nil。如果是這樣，那么當你隱式地解開它時，UIImage(data: data!)你會崩潰。

正如 Jacob 在評論中所說，您需要了解更多關于隱式解包的選項。為了讓你開始，你可以像這樣構建你的代碼：

if let url = URL(string: profPicURL) {
    DispatchQueue.global().async {
        if let data = try? Data(contentsOf: url),
           let image = UIImage(data: data)?.potter_circle
        {
            DispatchQueue.main.async {
                self.businessProfilePicture.contentMode = UIView.ContentMode.scaleAspectFill
                self.businessProfilePicture.image = image
            }
        } else {
            // raise an an error or set self.businessProfilePicture.image to a generic image or something
        }
    }
} else {
    // raise an an error or set self.businessProfilePicture.image to a generic image or something
}

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