Swift 2.3 NSFetchRequest

Question

自从从 2.2 迁移到 2.3 后，我现在收到以下错误：

"Extra Argument in call" in the following code:

class func objectCountForEntity (entityName:String, context:NSManagedObjectContext) -> Int {

let request = NSFetchRequest(entityName: entityName)
var error:NSError?
let count = context.countForFetchRequest(request, error: &error)

if let _error = error {
  print("\(#function) Error: \(_error.localizedDescription)")
} else {
  print("There are \(count) \(entityName) object(s) in \(context)")
}
return count
}

谁能告诉我如何在 swift 2.3 中获取实体计数，因为 countForFetchRequest 不再像在 swift 2.2

中那样工作

Answer 1

Swift 3.1

这是我的工作。

class func objectCountForEntity (entityName:String, context:NSManagedObjectContext) -> Int {

let request = NSFetchRequest(entityName: entityName)
var error:NSError?
let count = try! context.count(for: request)

if let _error = error {
    print("\(#function) Error: \(_error.localizedDescription)")
} else {
    print("There are \(count) \(entityName) object(s) in \(context)")
}
return count
}