如何使用选项字典关闭Swift中的Core Data Write-Ahead日志记录？

Question

如何使用Apples新的编程语言Swift关闭Core Data中的SQLite Write ahead logging(WAL)？

在ObjC中,我曾经在选项字典中传入键值对@"journal_mode":@"DELETE":

[storeCoordinator addPersistentStoreWithType:NSSQLiteStoreType
                               configuration:nil
                                         URL:[self databaseURL]
                                     options:@{NSMigratePersistentStoresAutomaticallyOption: @YES,
                                           NSInferMappingModelAutomaticallyOption: @YES,
                                           @"journal_mode": @"DELETE"}
                                       error:&error]

但是在Swift中,NSDictionary中只允许相同的类型,因此混合BOOL(映射到NSNumber)和NSString是不可能的.

有任何想法吗？

Answer 1

这些答案很接近,但实际上对我来说都没有.以下工作正常.该选项必须与a一样NSSQLitePragmasOption.

var options = Dictionary<NSObject, AnyObject>()
options[NSMigratePersistentStoresAutomaticallyOption] = true
options[NSInferMappingModelAutomaticallyOption] = true
options[NSSQLitePragmasOption] = ["journal_mode" : "DELETE"]
if coordinator!.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url, options: options, error: &error) == nil {
    ...
}

Answer 2

默认情况下,Swift词典是强类型的,但您可以定义词典应接受的类型.

var options = Dictionary<NSObject, AnyObject>()
options[NSMigratePersistentStoresAutomaticallyOption] = true
options[NSInferMappingModelAutomaticallyOption] = true
options["journal_mode"] = "DELETE"

[storeCoordinator addPersistentStoreWithType:NSSQLiteStoreType
                               configuration:nil
                                         URL:[self databaseURL]
                                     options:opitons
                                       error:&error]

如果您不确定函数期望的字典类型,请查看函数声明:

func addPersistentStoreWithType(_ storeType: String!,
   configuration configuration: String!,
       URL storeURL: NSURL!,
    options options: [NSObject : AnyObject]!,
        error error: AutoreleasingUnsafePointer<NSError?>) -> NSPersistentStore!

它准确描述了它所期望的字典类型 - Dictionary<NSObject, AnyObject>.

事实上,任何从Objective-C桥接的字典都将以这种方式输入.来自Apple Docs:

Swift还自动在Dictionary类型和NSDictionary类之间架起桥梁.当您从NSDictionary对象桥接到Swift词典时,生成的字典的类型为[NSObject:AnyObject].

您可以将任何NSDictionary对象桥接到Swift字典,因为所有Objective-C对象都是AnyObject兼容的.回想一下,如果一个对象是Objective-C或Swift类的实例,或者它可以桥接到一个对象,则该对象是AnyObject兼容的.所有NSDictionary对象都可以桥接到Swift词典,因此Swift编译器在导入Objective-C API时用[NSObject:AnyObject]替换NSDictionary类.

同样,当您在Objective-C代码中使用Swift类或协议时,导入器将与Objective-C兼容的Swift字典重新映射为NSDictionary对象.