Question

我有一个自定义对象的列表，我希望通过将其传递给函数来更改它的值：我的代码如下：

func UpdateButtonPressed(_Url : String,referenceArray: inout Array<Item>)
{

    var _itemList = [Item]()
    var result:String! = ""
    let url = URL(string:_Url)
    var request = URLRequest(url: url! as URL)
    request.httpMethod = "POST"
    request.addValue("application/json", forHTTPHeaderField: "Content-Type")
    request.addValue("application/json", forHTTPHeaderField: "Accept")

    let session = URLSession.shared
    let task = session.dataTask(with: request, completionHandler: { (data, response, error) in
        guard data != nil else {
            print("no data found: \(error)")
            return }
        do {
            let temp = NSString(data: data!, encoding: String.Encoding.utf8.rawValue)
            result = String(describing: temp!)
            DispatchQueue.main.async {
               referenceArray.append(contentsOf:  self.UpdateItem(result:result))
            }
        }
    })
    task.resume()
}

func UpdateItem(result:String)-> [Item]
{
    var _itemList = [Item]()
    _itemList = Item.ConvertJSONToItemList(result: result)
    return _itemList
}

我将我的功能调用如下：

 var mostRecent = [Item]()
       UpdateButtonPressed(_Url:PublicVariables.GetMostRecent(), referenceArray: &mostRecent)

但它没有用，我怎么能这样做？

Answer 1

您可以尝试完成

      func UpdateButtonPressed(_ Url : String , completion: @escaping (_ arr: [Item]) -> Void)       
      {

        var _itemList = [Item]()
        var result:String! = ""
        let url = URL(string:_Url)
        var request = URLRequest(url: url! as URL)
        request.httpMethod = "POST"
        request.addValue("application/json", forHTTPHeaderField: "Content-Type")
        request.addValue("application/json", forHTTPHeaderField: "Accept")

        let session = URLSession.shared
        let task = session.dataTask(with: request, completionHandler: { (data, response, error) in
            guard data != nil else {
                print("no data found: \(error)")
                return }
            do {
                let temp = NSString(data: data!, encoding: String.Encoding.utf8.rawValue)
                result = String(describing: temp!)
                DispatchQueue.main.async {

                    completion(self.UpdateItem(result:result))

                }
            }
        })
        task.resume()

 }

像这样打电话

    UpdateButtonPressed("") { (items) in

    }

Answer 2

问题的开始是你正在使用反模式。您应该努力使您的功能成为第一级功能（输入和输出）。你可以通过使用完成块或类似光明的未来或rx swift来解决这个问题。无论如何，你需要摆脱inout参数。

看一下这个链接：

https://thatthinginswift.com/completion-handlers/

https://github.com/ReactiveX/RxSwift

https://github.com/Thomvis/BrightFutures

Swift：如何通过引用函数传递对象数组

2 个答案: