ios - 核心数据验证 : from Objective-C to Swift

Question

我正在构建一个虚拟 iOS 项目，以便了解如何使用 Swift 在 Core Data 中实现验证。该项目的核心数据模型有一个名为 Person 的实体，它包含两个属性:firstName 和 lastName。该项目基于 Swift，但为了启动它，我使用 Objective-C 定义 NSManagedObject 子类:

Person.h

@interface Person : NSManagedObject

@property (nonatomic, retain) NSString *firstName;
@property (nonatomic, retain) NSString *lastName;

@end

Person.m

@implementation Person

@dynamic firstName;
@dynamic lastName;    

-(BOOL)validateFirstName:(id *)ioValue error:(NSError **)outError {
    if (*ioValue == nil || [*ioValue isEqualToString: @""]) {
        if (outError != NULL) {
            NSString *errorStr = NSLocalizedStringFromTable(@"First name can't be empty", @"Person", @"validation: first name error");
            NSDictionary *userInfoDict = @{ NSLocalizedDescriptionKey : errorStr };
            NSError *error = [[NSError alloc] initWithDomain:@"Domain" code: 101 userInfo: userInfoDict];
            *outError = error;
        }
        return NO;
    }
    return YES;
}

@end

Person-Bridging-Header.h

#import "Person.h"

在核心数据模型编辑器中，我在数据模型检查器中设置了实体类，如下所示:

class: Person

第一次启动项目时，我在 AppDelegate application:didFinishLaunchingWithOptions: 方法中创建了一个 Person 的实例，代码如下:

if !NSUserDefaults.standardUserDefaults().boolForKey("isNotInitialLoad") {
    let person = NSEntityDescription.insertNewObjectForEntityForName("Person", inManagedObjectContext: managedObjectContext!) as Person
    person.firstName = "John"
    person.lastName = "Doe"

    var error: NSError?
    if !managedObjectContext!.save(&error) {
        println("Unresolved error \(error), \(error!.userInfo)")
        abort()
    }

    NSUserDefaults.standardUserDefaults().setBool(true, forKey: "isNotInitialLoad")
    NSUserDefaults.standardUserDefaults().synchronize()
}

项目有一个UIViewController，代码如下:

class ViewController: UIViewController {

    var managedObjectContext: NSManagedObjectContext!
    var person: Person!

    override func viewDidLoad() {
        super.viewDidLoad()

        //Fetch the Person object
        var error: NSError?
        let fetchRequest = NSFetchRequest(entityName: "Person")
        let array = managedObjectContext.executeFetchRequest(fetchRequest, error:&error)
        if array == nil {
            println("Unresolved error \(error), \(error!.userInfo)")
            abort()
        }
        person = array![0] as Person
    }

    @IBAction func changeFirstName(sender: AnyObject) {
        //Generate a random firstName
        let array = ["John", "Jimmy", "James", "Johnny", ""]
        person.firstName = array[Int(arc4random_uniform(UInt32(5)))]

        var error: NSError?
        if !managedObjectContext.save(&error) {
            println("Unresolved error \(error), \(error!.userInfo)")
            return
        }

        //If success, display the new person's name
        println("\(person.firstName)" + " " + "\(person.lastName)")
    }

}

changeFirstName: 链接到 UIButton。因此，每当我单击此按钮时，都会随机生成一个新的 String 并将其分配给 person.firstName。如果这个新的 String 为空，validateFirstName:error: 生成一个 NSError 并且保存操作失败。

这很好用，但是为了拥有一个纯 Swift 项目，我决定删除 Person.h、Person.m 和 Person- Bridging-Header.h 并用单个 Swift 文件替换它们:

class Person: NSManagedObject {

    @NSManaged var firstName: String
    @NSManaged var lastName: String

    func validateFirstName(ioValue: AnyObject, error: NSErrorPointer) -> Bool {
        if ioValue as? String == "" {
            if error != nil {
                let myBundle = NSBundle(forClass: self.dynamicType)
                let errorString = myBundle.localizedStringForKey("First name can't be empty", value: "validation: first name error", table: "Person")
                let userInfo = NSMutableDictionary()
                userInfo[NSLocalizedFailureReasonErrorKey] = errorString
                userInfo[NSValidationObjectErrorKey] = self
                var validationError = NSError(domain: "Domain", code: NSManagedObjectValidationError, userInfo: userInfo)
                error.memory = validationError
            }
            return false
        }

        return true
    }

}

在核心数据模型编辑器中，我还更改了数据模型检查器中的实体类，如下所示:

class: Person.Person //<Project name>.Person

现在的问题是每当我调用changeFirstName: 时项目就会崩溃。最奇怪的是，如果我在 validateFirstName: 中放置一个断点，我可以看到此方法从未被调用。

我做错了什么？

Answer 1

我在这里有点猜测，但是 (id *)ioValue 参数映射到 Swift 为

ioValue: AutoreleasingUnsafeMutablePointer<AnyObject?>

因此 Swift 变体应该看起来像

func validateFirstName(ioValue: AutoreleasingUnsafeMutablePointer<AnyObject?>, error: NSErrorPointer) -> Bool {
    if let firstName = ioValue.memory as? String {
        if firstName == "" {
            // firstName is empty string
            // ...
        }
    } else {
        // firstName is nil (or not a String)
        // ...
    }
    return true
}

Swift 2 更新:

func validateFirstName(ioValue: AutoreleasingUnsafeMutablePointer<AnyObject?>) throws {
    guard let firstName = ioValue.memory as? String where firstName != ""  else {
        // firstName is nil, empty, or not a String
        let errorString = "First name can't be empty"
        let userDict = [ NSLocalizedDescriptionKey: errorString ]
        throw NSError(domain: "domain", code: NSManagedObjectValidationError, userInfo: userDict)
    }
    // firstName is a non-empty string
}

正如@SantaClaus 正确注意到的那样，验证函数现在必须 如果验证失败则抛出错误。