RxJs 捕获错误并继续 [英] RxJs catch error and continue

问题描述

我有一个要解析的项目列表，但其中一个的解析可能会失败.

I have a list of items to parse, but the parsing of one of them can fail.

捕获错误但继续执行序列的Rx-Way"是什么

What is the "Rx-Way" to catch error but continue executing the sequence

代码示例:

var observable = Rx.Observable.from([0,1,2,3,4,5])
.map(
  function(value){
      if(value == 3){
        throw new Error("Value cannot be 3");
      }
    return value;
  });

observable.subscribe(
  function(value){
  console.log("onNext " + value);
  },
  function(error){
    console.log("Error: " + error.message);
  },
  function(){
    console.log("Completed!");
  });

<script src="https://cdnjs.cloudflare.com/ajax/libs/rxjs/4.0.6/rx.all.js"></script>

我想以非 Rx 方式做什么:

What I want to do in a non-Rx-Way:

var items = [0,1,2,3,4,5];

for (var item in items){
  try{
    if(item == 3){
      throw new Error("Value cannot be 3");
    }
    console.log(item);
  }catch(error){
     console.log("Error: " + error.message);
  }
}

提前致谢

推荐答案

我建议您使用 flatMap(现在 rxjs 版本 5 中的 mergeMap)代替，这将如果您不关心它们，让您折叠错误.实际上，您将创建一个内部 Observable，如果发生错误，它可以被吞下.这种方法的优点是您可以将运算符链接在一起，如果管道中的任何地方发生错误，它都会自动转发到 catch 块.

I would suggest that you use flatMap (now mergeMap in rxjs version 5) instead, which will let you collapse errors if you don't care about them. Effectively, you will create an inner Observable that can be swallowed if an error occurs. The advantage of this approach is that you can chain together operators and if an error occurs anywhere in the pipeline it will automatically get forwarded to the catch block.

const {from, iif, throwError, of, EMPTY} = rxjs;
const {map, flatMap, catchError} = rxjs.operators;

// A helper method to let us create arbitrary operators
const {pipe} = rxjs;

// Create an operator that will catch and squash errors
// This returns a function of the shape of Observable<T> => Observable<R>
const mapAndContinueOnError = pipe(
  //This will get skipped if upstream throws an error
  map(v => v * 2),
  catchError(err => {
    console.log("Caught Error, continuing")
    //Return an empty Observable which gets collapsed in the output
    return EMPTY;
  })
)

const observable = from([0, 1, 2, 3, 4, 5]).pipe(
  flatMap((value) => 
    iif(() => value != 3, 
      of(value), 
      throwError(new Error("Value cannot be 3"))
    ).pipe(mapAndContinueOnError)
  )
);

observable.subscribe(
  (value) => console.log("onNext " + value), (error) => console.log("Error: " + error.message), () => console.log("Completed!")
);

<script src="https://unpkg.com/rxjs@7.0.0/dist/bundles/rxjs.umd.min.js"></script>

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