該行的CoreData更新導致插入空白行

Question

我正在學習如何使用CoreData並面臨以下問題。

我已經創建了這個函數，它應該更新現有的行或插入新的行。但是，當我試圖更新現有的應用程序時，應用程序會插入空白行。

這是我的代碼部分：

func saveSettingToDatabase() 
{ 
    guard settingNameLabel.text != nil else {return} 

    let context = AppDelegate.viewContext 
    let tableContext = SettingsTable(context: context) 

    // Get record if already exists 
    let request: NSFetchRequest<SettingsTable> = SettingsTable.fetchRequest() 
    let searchString = settingNameLabel.text! 
    request.predicate = NSPredicate(format: "settingName = %@", searchString) 
    let fetchResult = try? context.fetch(request) 

    //If record exists, update it. Else - insert. 
    if fetchResult?.count == 1 { 
     let change = fetchResult?[0] 
     change?.setValue(settingNameLabel.text, forKey: "settingName") 
     change?.setValue(settingValueLabel.text, forKey: "settingValue") 
     change?.setValue(booleanValueSwich.isOn, forKey: "booleanValue") 
     try? context.save() 
    } else 
    { 
     tableContext.settingName = settingNameLabel.text 
     tableContext.settingValue = settingValueLabel.text 
     tableContext.booleanValue = booleanValueSwich.isOn 
     context.insert(tableContext) 
     try? context.save() 
    } 
} 

一步一步：

1. 打開應用程序。

2. 用test1填充settingNameLabel。

3. 單擊獲取按鈕。

4. 值出現在各自的文本框中。這裏是數據庫的屏幕截圖更新之前：

before update

變化settingValueLabel.text到test999的值。

單擊保存。

根據以下屏幕截圖 - 值已更改，但應用程序添加了空白行（第1行）。

after update

我已經把這裏斷點：

context.insert(tableContext) 

但我的程序永遠放在這裏。而且在我的班級裏沒有其他的插頁可以完成。

有人可以提醒嗎？

Answer 1

我發現這個建議很有幫助：Swift Core Data adding extra empty row 所以我在我的SettingsTable類中實現了awakeFromInsert函數。調試後我可以看到插入是在這裏初始化：

let tableContext = SettingsTable(context: context) 

我已經將此行移入else語句，它現在可以正常工作。

func saveSettingToDatabase() 
{ 
    guard settingNameLabel.text != nil else {return} 

    let context = AppDelegate.viewContext 

    // Get record if already exists 
    let request: NSFetchRequest<SettingsTable> = SettingsTable.fetchRequest() 
    let searchString = settingNameLabel.text! 
    request.predicate = NSPredicate(format: "settingName = %@", searchString) 
    let fetchResult = try? context.fetch(request) 

    //If record exists, update it. Else - insert. 
    if fetchResult?.count == 1 { 
     let change = fetchResult?[0] 
     change?.setValue(settingNameLabel.text, forKey: "settingName") 
     change?.setValue(settingValueLabel.text, forKey: "settingValue") 
     change?.setValue(booleanValueSwich.isOn, forKey: "booleanValue") 
     try? context.save() 
    } else 
    { 
     let tableContext = SettingsTable(context: context) 
     tableContext.settingName = settingNameLabel.text 
     tableContext.settingValue = settingValueLabel.text 
     tableContext.booleanValue = booleanValueSwich.isOn 
     context.insert(tableContext) 
     try? context.save() 
    } 
} 

經過一番重構本功能看起來會更清楚：

func saveSettingToDatabase() 
{ 
    let context = AppDelegate.viewContext 
    // Get record if already exists 
    let request: NSFetchRequest<SettingsTable> = SettingsTable.fetchRequest() 
    request.predicate = NSPredicate(format: "settingName = %@", settingNameTextField.text!) 
    let fetchResult = try? context.fetch(request) 

    //If record exists, update it. Else - insert. 
    if fetchResult?.count == 1 { 
     let change = fetchResult?[0] 
     change?.settingName = settingNameTextField.text 
     change?.settingValue = settingValueTextField.text 
     change?.settingBooleanValue = settingBooleanValueSwitch.isOn 
     try? context.save() 
    } else 
    { 
     let addRecord = SettingsTable(context: context) 
     addRecord.settingName = settingNameTextField.text 
     addRecord.settingValue = settingValueTextField.text 
     addRecord.settingBooleanValue = settingBooleanValueSwitch.isOn 
     context.insert(addRecord) 
     try? context.save() 
    } 
}