ios - 如何从 swift 2 中的核心数据中删除值

Question

例如，这是我添加值的代码部分

do {
        let request = NSFetchRequest<NSFetchRequestResult>(entityName: "users")
        let results = try context.executeFetchRequest(request)

        if results.count > 0 {
            for item in results as! [NSManagedObject] {
                let fName = item.valueForKey("firstName")
                let lName = item.valueForKey("lastName")
                print(lName!, lName!)
            }
        }

    } catch {
        print("There was error getting data")
    }

假设我有 10 个用户，现在我想

1. 删除lastName为“DOW”的用户
2.前2位用户和后2位用户？
3. 此外，所有 lastName 的用户都以“D”开头

谢谢博尔纳

Answer 1

你可以编码:

if results.count > 0 {
    for item in results as! [NSManagedObject] {
        let fName = item.valueForKey("firstName") as! String
        let lName = item.valueForKey("lastName")
        print(lName!, lName!)
        if fName.contains("DOW"){
            appDelegate.managedObjectContext.deleteObject(item)
        }
    }
}

或者只是获取你想要的对象 NSPredicate 并删除它代码:

let fetchRequest = NSFetchRequest(entityName: "users")
    fetchRequest.predicate = NSPredicate(format: "firstName beginswith[c] %@", "D")
    fetchRequest.returnsObjectsAsFaults = false
    do{
        let fetchResults = try appDelegate.managedObjectContext..executeFetchRequest(fetchRequest)
        if fetchResults.count>0 {
              appDelegate.managedObjectContext.deleteObject(fetchResults[0])
        } else {
            // no data
        }
    }catch{
        //error
    }