Generics 带泛型的Swift-Fetch方法
其思想是使用Coredata获取“类型化”数据 已更新Generics 带泛型的Swift-Fetch方法,generics,core-data,swift,Generics,Core Data,Swift,其思想是使用Coredata获取“类型化”数据 已更新 class func retrieve<T: AnyObject>(entityName:T.Type, sortBy:String? = nil, isAscending:Bool? = true, predicate:NSPredicate? = nil) -> AnyObject[] { println("\(entityName)") let request = NSFetchRequest
class func retrieve<T: AnyObject>(entityName:T.Type, sortBy:String? = nil, isAscending:Bool? = true, predicate:NSPredicate? = nil) -> AnyObject[] {
println("\(entityName)")
let request = NSFetchRequest(entityName: "Users")
request.returnsObjectsAsFaults = false
if predicate != nil {
request.predicate = predicate
}
if (sortBy != nil){
var sorter: NSSortDescriptor = NSSortDescriptor(key: sortBy , ascending: isAscending!)
request.sortDescriptors = [sorter]
}
var error: NSError? = nil
var fetchedResult = myDataModel.managedObjectContext.executeFetchRequest(request, error: &error)
if !error {
println("errore: \(error)")
}
println("retrieved \(fetchedResult.count) elements for \(entityName)")
return fetchedResult
}
在哪里
您有什么建议吗?您可以使用
NSStringFromClass
,只要您使用@objc(ModelClassName)
另一个对您来说更重要的选项可能是:
protocol EntityWithName {
class func entityName() -> String
}
extension MyModelObject : EntityWithName {
class func entityName() -> String {
return "MyModelObject"
}
}
extension NSManagedObjectContext {
// Create an instance of T and insert it into the Context (this is normal)
func insert<T:NSManagedObject where T:EntityWithName>(entityClass:T.Type) -> T? {
let entityDescription = NSEntityDescription.entityForName(entityClass.entityName(), inManagedObjectContext: self)
if !entityDescription {
return nil
}
return NSManagedObject(entity: entityDescription, insertIntoManagedObjectContext: self) as? T
}
}
let myModelObject = myContext.insert(MyModelObject.Self)
对于每个用户可修改的类文件(而不是uu1),这应该没问题,因为mogenerator生成entityName类方法。您可以使用
NSStringFromClass
,只要使用@objc(ModelClassName)
另一个对您来说更重要的选项可能是:
protocol EntityWithName {
class func entityName() -> String
}
extension MyModelObject : EntityWithName {
class func entityName() -> String {
return "MyModelObject"
}
}
extension NSManagedObjectContext {
// Create an instance of T and insert it into the Context (this is normal)
func insert<T:NSManagedObject where T:EntityWithName>(entityClass:T.Type) -> T? {
let entityDescription = NSEntityDescription.entityForName(entityClass.entityName(), inManagedObjectContext: self)
if !entityDescription {
return nil
}
return NSManagedObject(entity: entityDescription, insertIntoManagedObjectContext: self) as? T
}
}
let myModelObject = myContext.insert(MyModelObject.Self)
对于每个用户可修改的类文件(而不是uu1),应该没有问题,因为mogenerator生成entityName类方法。如果如@David所指出的,将
@objc(ModelClassName)
添加到模型类中,下面是一个简化版本:
func retrieve<T: NSManagedObject>(entityClass:T.Type, sortBy:String? = nil, isAscending:Bool = true, predicate:NSPredicate? = nil) -> T[] {
let entityName = NSStringFromClass(entityClass)
let request = NSFetchRequest(entityName: entityName)
request.returnsObjectsAsFaults = false
request.predicate = predicate
if (sortBy != nil) {
var sorter = NSSortDescriptor(key:sortBy , ascending:isAscending)
request.sortDescriptors = [sorter]
}
var error: NSError? = nil
var fetchedResult = myDataModel.managedObjectContext.executeFetchRequest(request, error: &error)
if !error {
println("errore: \(error)")
}
println("retrieved \(fetchedResult.count) elements for \(entityName)")
return fetchedResult
}
如@David所指出的,如果将
@objc(ModelClassName)
添加到模型类中,那么下面是一个简化版本:
func retrieve<T: NSManagedObject>(entityClass:T.Type, sortBy:String? = nil, isAscending:Bool = true, predicate:NSPredicate? = nil) -> T[] {
let entityName = NSStringFromClass(entityClass)
let request = NSFetchRequest(entityName: entityName)
request.returnsObjectsAsFaults = false
request.predicate = predicate
if (sortBy != nil) {
var sorter = NSSortDescriptor(key:sortBy , ascending:isAscending)
request.sortDescriptors = [sorter]
}
var error: NSError? = nil
var fetchedResult = myDataModel.managedObjectContext.executeFetchRequest(request, error: &error)
if !error {
println("errore: \(error)")
}
println("retrieved \(fetchedResult.count) elements for \(entityName)")
return fetchedResult
}
我似乎无法让
@objc
注释为我工作,因此我使用了:
let fetchRequest = NSFetchRequest(entityName: NSStringFromClass(entityClass).componentsSeparatedByString(".").last!)
这可以深入到实体名称。我似乎无法让
@objc
注释对我起作用,因此我使用了:
let fetchRequest = NSFetchRequest(entityName: NSStringFromClass(entityClass).componentsSeparatedByString(".").last!)
这可以深入到实体名称。如果我能向David征求您的意见,我不会使用绑定到objective-c。我认为关于“然而,由于您的模型对象需要将NSManagedObject作为一个超类,因此试图避免“绑定到objective-c”实际上是毫无意义的”,所以一个好的解决方案是Jean an您向我提出的:使用注释@objc(Users)和NSStringFromClass。更清楚。我喜欢这个而不是分机。您关于插入的解决方案与我根据您之前的建议采用的相同(没有EntityWithName)。如果我征求大卫的意见,我不会使用objective-c的绑定。我认为关于“然而,由于您的模型对象需要将NSManagedObject作为一个超类,因此试图避免“绑定到objective-c”实际上是毫无意义的”,所以一个好的解决方案是Jean an您向我提出的:使用注释@objc(Users)和NSStringFromClass。更清楚。我喜欢这个而不是分机。您关于插入的解决方案与我根据您之前的建议采用的相同(没有EntityWithName)。谢谢
@objc(Client)
class Client : NSManagedObject {
...
}
retrieve(Client) // This would get all clients in the database.
let fetchRequest = NSFetchRequest(entityName: NSStringFromClass(entityClass).componentsSeparatedByString(".").last!)