Swift 2.3 NSFetchRequest

Question

由于从2.2迁移到2.3，我现在得到了以下错误：

以下代码中的“调用中的额外参数”：

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
}

有谁能建议我如何获得一个实体，因为countForFetchRequest不再像它在Swid2.2中那样起作用

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
}