swift - 使用未解析的标识符

Question

大家可以帮忙解决这个错误吗？我正在使用 CoreData。我的这段代码有错误。具体在代码的最后一部分(返回项)。错误描述告诉我们使用了未解析的标识符“items”

class func fetchEntities(className:NSString, withPredicate predicate:NSPredicate?, managedObjectContext:NSManagedObjectContext)->NSArray{
    let fetchRequest:NSFetchRequest = NSFetchRequest()
    let entetyDescription:NSEntityDescription = NSEntityDescription.entityForName(className as! String, inManagedObjectContext: managedObjectContext)!

    fetchRequest.entity = entetyDescription

    if predicate != nil{
        fetchRequest.predicate = predicate!
    }

    fetchRequest.returnsObjectsAsFaults = false


    do{
       let items = try managedObjectContext.executeFetchRequest(fetchRequest)

    } catch {

        print("error")

    }
    return items
}

具体错误代码为

返回

Answer 1

您在 do {} block 中初始化了 item，因此函数中的项目不知道 item 变量是什么，因此您应该在函数的开头初始化 item 变量:-

class func fetchEntities(className:NSString, withPredicate predicate:NSPredicate?, managedObjectContext:NSManagedObjectContext)->NSArray{
let items: NSArray!
let fetchRequest:NSFetchRequest = NSFetchRequest()
let entetyDescription:NSEntityDescription = NSEntityDescription.entityForName(className as! String, inManagedObjectContext: managedObjectContext)!

fetchRequest.entity = entetyDescription

if predicate != nil{
    fetchRequest.predicate = predicate!
}

fetchRequest.returnsObjectsAsFaults = false


do{
   items = try managedObjectContext.executeFetchRequest(fetchRequest)

} catch {

    print("error")

}
return items
}