在Swift 2中删除实体的核心数据

Question

如何在Swift中删除实体的核心数据中的所有条目？

我想要一个deleteAll（）方法，以便我可以清除数据库。

这是我到目前为止有：

func deleteAllCoreData() { 
    let fetchRequest = NSFetchRequest(entityName: "DataPoint") 
    let deleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest) 

    do { 
     try coordinator.executeRequest(deleteRequest, withContext: managedContext) 
    } catch let error as NSError { 
     print("Could not fetch \(error), \(error.userInfo)") 
    } 

} 

但它有一个错误：

Unknown command type (entity: DataPoint; predicate: ((null)); sortDescriptors: ((null)); type: NSManagedObjectIDResultType;) >

Answer 1

的iOS 9添加了一个名为NSBatchDeleteRequest新的类，它允许您轻松删除对象匹配的谓词而不必将它们全部加载到内存中。以下是你如何使用它：

let fetchRequest = NSFetchRequest(entityName: "Foo") 
let deleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest) 

do { 
    //`myPersistentStoreCoordinator` is from the core data stack 
    try myPersistentStoreCoordinator.executeRequest(deleteRequest, withContext: myContext) 
} catch let error as NSError { 
    // TODO: handle the error 
}