其思想是使用coredata获取“类型”数据。
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(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
}
现在,我在上面写的是语法上正确的,但我相信还有另一种方法可以做到,也许更“容易”。我想这个提议很明确:)
我试图从EntityName输入参数中获取类名
以下面的方式调用此函数或类似的方式调用此函数:
var xx = myDataModel.retrieve(Users.self)
在哪里?
Users: NSManagedeObject
你有什么建议吗?
最佳答案
如果像@david指出的那样,将@objc(ModelClassName)
添加到模型类中,那么这里有一个简化版本:
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
}
人们会这样使用它:
@objc(Client)
class Client : NSManagedObject {
...
}
retrieve(Client) // This would get all clients in the database.
关于generics - Swift-泛型提取方法,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/24393837/