Swift：调用中的额外参数'错误' [英] Swift: Extra argument 'error' in call

问题描述

我目前正在使用Swift 2.0和Xcode Beta 2开发我的第一个iOS应用程序。它读取外部JSON并在数据表格视图中生成列表。但是，我得到了一个我似乎无法解决的奇怪的小错误：

I'm currently developing my first iOS app using Swift 2.0 and Xcode Beta 2. It reads an external JSON and generates a list in a table view with the data. However, I'm getting a strange little error that I can't seem to fix:

Extra argument 'error' in call

以下是我的代码片段：

let task = session.dataTaskWithURL(url!, completionHandler: {data, response, error -> Void in
            print("Task completed")

            if(error != nil){
                print(error!.localizedDescription)
            }

            var err: NSError?

            if let jsonResult = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: &err) as? NSDictionary{

                if(err != nil){
                    print("JSON Error \(err!.localizedDescription)")
                }

                if let results: NSArray = jsonResult["results"] as? NSArray{
                    dispatch_async(dispatch_get_main_queue(), {
                        self.tableData = results
                        self.appsTableView!.reloadData()
                    })
                }
            }
        })

此行引发错误：

if let jsonResult = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: &err) as? NSDictionary{

有人可以告诉我这里我做错了吗？

Can someone please tell me what I'm doing wrong here?

推荐答案

使用 Swift 2 ，签名 NSJSONSerialization 已更改，以符合新的错误处理系统。

With Swift 2, the signature for NSJSONSerialization has changed, to conform to the new error handling system.

以下是如何使用它的示例：

Here's an example of how to use it:

do {
    if let jsonResult = try NSJSONSerialization.JSONObjectWithData(data, options: []) as? NSDictionary {
        print(jsonResult)
    }
} catch let error as NSError {
    print(error.localizedDescription)
}

Swift 3 ， NSJSONSerialization的名称 Swift API设计指南，code>及其方法已发生变化。

With Swift 3, the name of NSJSONSerialization and its methods have changed, according to the Swift API Design Guidelines.

以下是相同的例子：

do {
    if let jsonResult = try JSONSerialization.jsonObject(with: data, options: []) as? [String:AnyObject] {
        print(jsonResult)
    }
} catch let error as NSError {
    print(error.localizedDescription)
}

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