swift - 类型 'NSFetchRequest' 的值没有成员 'performFetch'

Question

我写代码

    var fetchRequest: NSFetchRequest = NSFetchRequest(entityName: "Doctor")
    fetchRequest.predicate = NSPredicate(format: "id != nil")



let sortDescriptors: [NSSortDescriptor] = [(NSSortDescriptor.init(key: "distance", ascending: true)), (NSSortDescriptor.init(key: "lastname", ascending: true))]
fetchRequest.sortDescriptors = sortDescriptors

var error: NSError? = nil

//显示错误“NSFetchRequest”类型的值没有成员“performFetch”

var fetchSuccessful: Bool = fetchRequest.performFetch(error)

Answer 1

@Magdalena Dziesińska:在你的代码中......

var fetchSuccessful: Bool = fetchRequest.performFetch(error)

“performFetch”不存在。要处理错误(错误处理)，请将其放在“do-try-catch 语句”中，例如在你的代码之后...

 var fetchRequest: NSFetchRequest = NSFetchRequest(entityName: "Doctor")
fetchRequest.predicate = NSPredicate(format: "id != nil")

let sortDescriptors: [NSSortDescriptor] = [(NSSortDescriptor.init(key: "distance", ascending: true)), (NSSortDescriptor.init(key: "lastname", ascending: true))] fetchRequest.sortDescriptors = sortDescriptors

使用以下 do-try-catch 语句捕获任何错误并获取获取请求。

do {
        let results = try context.executeFetchRequest(request)
    } catch {
        print("requesting error")
    }

注意:请求是您放置“fetchRequest”的位置