如何在不中止序列的情况下仅捕获特定类型的异常 [英] How to catch only specific type of exception without abort the sequence

问题描述

RxJs 似乎没有允许捕获特定类型异常的 catch() 方法的变体.但是很多时候我发现自己处于需要这样的操作员的境地.

RxJs does not seem to have a variation of catch() method which allow to capture only certain type of exception. But many times I found myself in a situation where such operator is needed.

例如，成像我需要解析日志文件的每一行并打印解析的消息.日志文件的某些行可能已损坏，但我真的不在乎，只想为该行输出日志消息已损坏"并继续下一行.

For example, imaging I need to parse each line of a log file and print the parsed message. Some lines of the log file might have been corrupted, but I really don't care and just want to output a "Log message corrupted" for such line and continue to the next line.

如果 catch() 确实允许我们指定特定类型的错误来捕获并传递所有其他错误，那么我们可以做一些类似下面的伪代码的事情

If catch() did allow us to specify a specific type of error to catch and pass through all other errors, we can then do some thing like pseudo-code below

readLogs()
.flatMap parseLog
.catchOnly ParseError, () ->
  'Log message corrupted'
.subscribe (logMessage) ->
  console.log logMessage

我想知道考虑到 catach() 的当前限制，RxJs 的正确方法是什么.

I was wondering what would be the proper way of RxJs to do that given the current limitation of catach().

推荐答案

您需要嵌套 catch 以防止错误终止整个链，并且您需要将逻辑分开分割和解析行:

You would need to nest catch in order to prevent an error from terminating the entire chain and you would need to separate the logic for splitting and parsing lines:

import {of, throwError} from 'rxjs'
import {flatMap, map, catchError} from 'rxjs/operators'



function handleErrors(e) {
    return (e instanceof ParseError) ? 
            of("Log message corrupted") : throwError(e);
}

readLogs().pipe(
  flatMap(splitLines)
  flatMap(line => 
    of(line).pipe(
      map(parseLine), 
      catch(handleErrors)
    )
  )
)
.subscribe(
  parsedLine => console.log(parsedLine),
  e => console.error('Fatal error: ' + e);
);

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