如何使用NSURLSession在Swift中解析JSON [英] How to parse JSON in Swift using NSURLSession

问题描述

我正在尝试解析JSON，但收到此错误:

I am trying to parse JSON but getting this error:

表达类型含糊不清，没有更多上下文

type of expression is ambiguous without more context

我的代码是:

func jsonParser() {

    let urlPath = "http://headers.jsontest.com/"
    let endpoint = NSURL(string: urlPath)
    let request = NSMutableURLRequest(URL:endpoint!)

    let session = NSURLSession.sharedSession()
    NSURLSession.sharedSession().dataTaskWithRequest(request){ (data, response, error) throws -> Void in

        if error != nil {
            print("Get Error")
        }else{
            //var error:NSError?
            do {
                let json:AnyObject =  try NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions(rawValue: 0)) as? NSDictionary

            print(json)

        } catch let error as NSError {
            // error handling
            print(error?.localizedDescription)
        }
        }
    }
    //task.resume()
}

在Xcode 6.4中没有尝试捕获就可以正常工作，但是在Xcode 7中却无法工作.

This is working fine with out try catch in Xcode 6.4 but this is not working in Xcode 7.

推荐答案

不要为解码对象声明AnyObject类型，因为您希望它成为NSDictionary，并且您正在执行转换以执行此操作

Don't declare an AnyObject type for your decoded object since you want it to be an NSDictionary and you're performing a conversion to do this.

此外，最好将零选项用于NSJSONSerialization，而不要使用随机选项.

Also it's better to use zero options for NSJSONSerialization instead of random ones.

在我的示例中，我还使用了一个自定义错误类型来进行演示.

In my example I've also used a custom error type just for demonstration.

请注意，如果您使用的是自定义错误类型，则还必须包含通用的catch才能详尽无遗(在此示例中，只需简单地向下转换为NSError).

Note, if you're using a custom error type, you have to also include a generic catch to be exhaustive (in this example, with a simple downcasting to NSError).

enum JSONError: String, ErrorType {
    case NoData = "ERROR: no data"
    case ConversionFailed = "ERROR: conversion from JSON failed"
}

func jsonParser() {
    let urlPath = "http://headers.jsontest.com/"
    guard let endpoint = NSURL(string: urlPath) else {
        print("Error creating endpoint")
        return
    }
    let request = NSMutableURLRequest(URL:endpoint)
    NSURLSession.sharedSession().dataTaskWithRequest(request) { (data, response, error) in
        do {
            guard let data = data else {
                throw JSONError.NoData
            }
            guard let json = try NSJSONSerialization.JSONObjectWithData(data, options: []) as? NSDictionary else {
                throw JSONError.ConversionFailed
            }
            print(json)
        } catch let error as JSONError {
            print(error.rawValue)
        } catch let error as NSError {
            print(error.debugDescription)
        }
   }.resume()
}

与Swift 3.0.2相同:

enum JSONError: String, Error {
    case NoData = "ERROR: no data"
    case ConversionFailed = "ERROR: conversion from JSON failed"
}

func jsonParser() {
    let urlPath = "http://headers.jsontest.com/"
    guard let endpoint = URL(string: urlPath) else {
        print("Error creating endpoint")
        return
    }
    URLSession.shared.dataTask(with: endpoint) { (data, response, error) in
        do {
            guard let data = data else {
                throw JSONError.NoData
            }
            guard let json = try JSONSerialization.jsonObject(with: data, options: []) as? NSDictionary else {
                throw JSONError.ConversionFailed
            }
            print(json)
        } catch let error as JSONError {
            print(error.rawValue)
        } catch let error as NSError {
            print(error.debugDescription)
        }
    }.resume()
}

这篇关于如何使用NSURLSession在Swift中解析JSON的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！