ios - 如何在 iOS 中使用 Sqllite 验证登录表单进入下一页?
问题描述
**this is to how to create a login validation form to move from login to next view controller **
**fetching the data from database**
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {
return
}
**it stores the data**
let managedContext = appDelegate.persistentContainer.viewContext
//it fetches the data
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Details")
**validation code to check it but the condition fails**
do {
let result = try managedContext.fetch(fetchRequest)
for data in result as! [NSManagedObject] {
if ([emailid.text].count != 0 && [password.text].count != 0){
if (emailid.text == data.value(forKey: "emailId") as? String) && (password.text == data.value(forKey: "passWord") as? String){
let secondvc = storyboard?.instantiateViewController(withIdentifier: "loginVcID") as! loginVc
self.navigationController?.pushViewController(secondvc, animated: true)
}
在这种情况下,它不会移动到下一个视图控制器 来检查另一个条件 } else { self.label.text = "enter a valid data" } }
}
**when it fails it goes to catch to show that**
catch
{
print("Failed")
}
}
}
**this code is for registration to save into database**
**to create a database and store the value**
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else { return }
let managedContext = appDelegate.persistentContainer.viewContext
let detailEntity = NSEntityDescription.entity(forEntityName: "Details", in: managedContext)!
** 创建数据库** let detail = NSManagedObject(entity: detailEntity, insertInto: managedContext) detail.setValue(username.text, forKeyPath: "userName") detail.setValue(emailid.text, forKey: "emailId") detail. setValue(password.text, forKey: "passWord") detail.setValue(city.text, forKey: "city")
**saving the data**
do {
try managedContext.save()
}
** it display whatever in that method**
catch let error as NSError
{
它在失败时显示错误 print("Could not save. (error), (error.userInfo)") }
解决方案
转到你的 appDelegate,你会发现一行 // MARK: - Core Data stack & // MARK: - Core Data Saving support, remove the saveContext() function & also remove persistentContainer.. 然后
将此类添加到您的项目中
final class PersistenceManager {
private init() {}
static let shared = PersistenceManager()
// MARK: - Core Data stack
lazy var persistentContainer: NSPersistentContainer = {
/*
The persistent container for the application. This implementation
creates and returns a container, having loaded the store for the
application to it. This property is optional since there are legitimate
error conditions that could cause the creation of the store to fail.
*/
let container = NSPersistentContainer(name: "ProjectNAME")
container.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let error = error as NSError? {
// Replace this implementation with code to handle the error appropriately.
// fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
/*
Typical reasons for an error here include:
* The parent directory does not exist, cannot be created, or disallows writing.
* The persistent store is not accessible, due to permissions or data protection when the device is locked.
* The device is out of space.
* The store could not be migrated to the current model version.
Check the error message to determine what the actual problem was.
*/
fatalError("Unresolved error \(error), \(error.userInfo)")
}
})
return container
}()
lazy var context = persistentContainer.viewContext
// MARK: - Core Data Saving support
func save() {
if context.hasChanges {
do {
try context.save()
} catch {
// Replace this implementation with code to handle the error appropriately.
// fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
let nserror = error as NSError
fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
}
}
}
func fetch<T: NSManagedObject>(_ objectType: T.Type) -> [T] {
let entityName = String(describing: objectType)
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entityName)
do {
let fetchedObjects = try context.fetch(fetchRequest) as? [T]
return fetchedObjects ?? [T]()
} catch {
return [T]()
}
}
func deleteAll<T: NSManagedObject>(_ objectType: T.Type) {
let entityName = String(describing: objectType)
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entityName)
let deleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
do {
try persistentContainer.persistentStoreCoordinator.execute(deleteRequest, with: context)
} catch {
print(error.localizedDescription)
}
}
func delete(_ object: NSManagedObject) {
context.delete(object)
save()
}
}
获取数据
PersistenceManager.shared.fetch(User.self)
删除数据
PersistenceManager.shared.delete(user)
创建用户
let newUser = Users(context: PersistenceManager.shared.context)
newUser.name = "Zero Cool"
newUser.password = "qwerty"
PersistenceManager.shared.save()
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