解码Dart中的捕获响应 [英] Decode a response from a catch in Dart

问题描述

我尝试解码从捕获返回的响应，这是我尝试的内容：

I try to decode the response returned from a catch, here is what I tried :

try{
  ...
} catch (err) {
    //JsonCodec codec = new JsonCodec(); // doesn't work
    //var decoded = codec.decode(err);
    ...
 }

错误：类型'_Exception'不是类型'字符串'的子类型

Error: type '_Exception' is not a subtype of type 'String'

print（err）：

print(err) :

例外：{
error：{
code： invalid_expiry_year
}
}

Exception: { "error": { "code": "invalid_expiry_year" } }

我想获取代码的值，我尝试了很多事情，但没有用，

I would like to get the value of "code", I tried many things but it doesn't work,

有什么想法吗？

 print(err.code);

然后我得到：

推荐答案

您可以获取 message 属性和 jsonDecode 它。

try {
} catch (e) {
  var message = e.message; // not guaranteed to work if the caught exception isn't an _Exception instance
  var decoded = jsonDecode(message);
  print(decoded['error']['code'])'
}

所有这些警告都是对 Exception 的滥用。请注意，您通常不要引发异常（消息）； 。将json编码的消息放入其中并不是传达有关异常的详细信息的最佳方法。而是编写一个 Exception 的自定义实现并捕获特定类型。

All of this strikes as a misuse of Exception. Note that you generally don't want to throw Exception(message);. Putting a json encoded message in there is not the best way to communicate details about the exception. Instead, write a custom implementation of Exception and catch the specific type.

class InvalidDataException implements Exception {
  final String code;
  InvalidDataException(this.code);
}

try {
} on InvalidDataException catch(e) {
  print(e.code); // guaranteed to work, we know the type of the exception
}

请参见< a href = https://api.dartlang.org/stable/2.1.0/dart-core/Exception-class.html rel = nofollow noreferrer> Exception ：

直接使用 new Exception（ message）<<不鼓励使用/ code>，并且仅在开发过程中将其作为临时措施使用，直到完成库使用的实际例外为止。

Creating instances of Exception directly with new Exception("message") is discouraged, and only included as a temporary measure during development, until the actual exceptions used by a library are done.

另请参见 https：/ /www.dartlang.org/guides/language/effective-dart/usage#avoid-catches-with-on-clauses

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