在Swift中使用JSONDecoder进行错误处理 [英] Error handling using JSONDecoder in Swift

问题描述

我在Swift中使用JSONDecoder()，需要获取更好的错误消息.

I am using JSONDecoder() in Swift and need to get better error messages.

在调试描述中(例如)，我可以看到诸如给定数据不是有效的JSON"之类的消息，但我需要知道这是错误原因，而不是网络错误(例如).

Within the debug description (for example) I can see messages like "The given data was not valid JSON", but I need to know it is that rather than a network error (for example).

    let decoder = JSONDecoder()
    if let data = data{
        do {
            // process data

        } catch let error {
           // can access error.localizedDescription but seemingly nothing else
    }

我试图转换为DecodingError，但这似乎并没有显示更多信息.我当然不需要字符串-甚至错误代码都比这有用得多...

I tried to cast to a DecodingError, but this does not seem to reveal more information. I certainly don't need the string - even an error code is much more helpful than this...

推荐答案

从不在解码catch块中打印error.localizedDescription.这将返回一个毫无意义的通用错误消息.始终打印error实例.然后，您会得到所需的信息.

Never print error.localizedDescription in a decoding catch block. This returns a quite meaningless generic error message. Print always the error instance. Then you get the desired information.

let decoder = JSONDecoder()
    if let data = data {
        do {
            // process data

        } catch  {
           print(error)
    }

或者对于完整组错误使用

let decoder = JSONDecoder()
if let data = data {
    do {
       // process data
    } catch let DecodingError.dataCorrupted(context) {
        print(context)
    } catch let DecodingError.keyNotFound(key, context) {
        print("Key '\(key)' not found:", context.debugDescription)
        print("codingPath:", context.codingPath)
    } catch let DecodingError.valueNotFound(value, context) {
        print("Value '\(value)' not found:", context.debugDescription)
        print("codingPath:", context.codingPath)
    } catch let DecodingError.typeMismatch(type, context)  {
        print("Type '\(type)' mismatch:", context.debugDescription)
        print("codingPath:", context.codingPath)
    } catch {
        print("error: ", error)
    }

这篇关于在Swift中使用JSONDecoder进行错误处理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！