Swift 4在完成处理程序中获得结果

Question

我有一个方法正在调用另一个具有完成处理程序的方法。

func getFilesAndDirectories(folder:String) -> Array<Dictionary<String, String>>
    {
        var returnedResults = Array<Dictionary<String, String>>()

        WebService().GetFilesAndDirectories(folder)
        {
            (result: Array<Dictionary<String, String>>) in

            DispatchQueue.main.async {

                returnedResults = result

            }

        }

        return returnedResults
    }

以下是我如何称呼它：

var filesDirectories = Array<Dictionary<String, String>>()

override func viewDidAppear(_ animated: Bool) {

        filesDirectories = getFilesAndDirectories(folder: "/")
        print(filesDirectories)
    }

但是当我打印filesDirectories时，它会返回[]

我的问题是，如何将getFilesAndDirectories的结果传递给filesDirectories？

Answer 1

func getFilesAndDirectories(folder:String, completionHandler:@escaping (_ result:Array<Dictionary<String, String>>) -> Void)
{
    var returnedResults = Array<Dictionary<String, String>>()

    WebService().GetFilesAndDirectories(folder)
    {
        (result: Array<Dictionary<String, String>>) in

        DispatchQueue.main.async {
            returnedResults = result

            completionHandler(returnedResults)
        }
    }
}

您可以使用以下相同的

var filesDirectories = Array<Dictionary<String, String>>()

override func viewDidAppear(_ animated: Bool) {
    getFilesAndDirectories(folder: "/") { result in
        self.filesDirectories = result
        print(filesDirectories)
    }
}

Answer 2

你可以这样做：

func getFilesAndDirectories(folder: String, completionHandler: @escaping (_ result: Array<Dictionary<String, String>>) -> ()) {

    WebService().GetFilesAndDirectories(folder) {
        (result: Array<Dictionary<String, String>>) in
            completionHandler(result)
        }
}

然后：

override func viewDidAppear(_ animated: Bool) {

    getFilesAndDirectories(folder: "/", completionHandler: ({
    (result) in 
        print(result)
    }))
}

您应该在completionHandler范围内拥有正确的值。