swift - 从 Swift 2.x 到 4.0 的代码迁移问题

Question

在我回顾 Swift 中的存储库项目后，我意识到存在一个代码问题，我很难找出与 MKLocalSearch 特定函数的 API 更改相关的错误

具体来说，在我的下面的代码片段中，主要包含函数，基本上执行搜索并更新到搜索位置

func searchBarSearchButtonClicked (_ searchBar: UISearchBar){
    //here check if local search existed, it then cancel the search
    if let search = localSearch {
        search.cancel()
    }
    let request = MKLocalSearchRequest()
    request.naturalLanguageQuery = searchBar.text

    localSearch = MKLocalSearch(request: request)
    //set the network activity visible
    UIApplication.shared
        .isNetworkActivityIndicatorVisible = true

    //start the search and deliver the response with error handling asynchronously

    /* --------------------------This is where the bug occurs --------------*/
    localSearch!.start {
        [weak self] (response : MKLocalSearchResponse?, error: NSError?) in

        if error != nil {
            return
        }

        UIApplication.shared.isNetworkActivityIndicatorVisible = false
        //safely extract location search results based on response
        guard let myResponse = response else {
            print("error in search: \(error?.localizedDescription ?? MissingError)")
            return
        }
        //            guard let location = myResponse.mapItems.first else {
        //                print("There are no results")
        //                return
        //            }
        guard let location = myResponse.mapItems else{
            print("There are no results")
            return
        }
        self?.updateMapWithItem(location, region: myResponse.boundingRegion)
    }

所以我收到了错误及其完整消息 Cannot convert value of type '(MKLocalSearchResponse?, NSError?) -> ()' to expected argument type 'MKLocalSearchCompletionHandler' (aka '(Optional<MKLocalSearchResponse>, Optional<Error>) -> ()')

Swift 3.0 编译器建议我执行以下操作，但它的解决方案完全足够，因为它只是不断告诉我插入越来越多的以下语句，而没有完全解决问题。 Insert ' as! MKLocalSearchCompletionHandler'

我实际上想将整个项目代码从 Swift 2.x 迁移到 4.0，但我的意思是我需要先弄清楚从 2.x 到 3.0 的迁移。

Answer 1

使用

localSearch?.start(completionHandler: {
    [weak self] (response, error) in
    ....
})

而不是

localSearch!.start {
    [weak self] (response : MKLocalSearchResponse?, error: NSError?) in
    ....
}