重试，然后忽略错误并获取源值 rxjs

Question

错误或没有错误，我想在重试后进入订阅成功处理程序。要进行测试，请注释掉 setTimeout 行。这将使 checkforText$ 始终抛出错误。我想忽略最后的错误，仍然 return 订阅成功处理程序的编辑器。

var editor = { innerText: "" }
var editorOpened$ = of(editor) // observe editor object

function checkforText(){
    return new Promise((resolve,reject) => {
        console.log('checking for text',editor)
    
        if (editor.innerText == ""){
            reject('No text');
        } else {
            resolve(editor)
        }
    })
}

var checkForText$ = defer( () => from(checkforText())) // observe text on editor object

// comment out this line out to test
setTimeout( _ => { editor.innerText = 'testing' }, 2000) 

editorOpened$.pipe( 
    switchMap(editor => 
        checkForText$.pipe(
            retryWhen(errors => {
                console.log ('no text found... retrying')
                return errors.pipe( 
                    delay(1000), 
                    take(3),
                )
            }),     
         )
     )  
).subscribe(editor => {
    console.log('FINISH CHECKING', editor)  
}, err => console.log('ERROR ',err))

找到文本时的输出（setTimeout 未注释掉）：

checking for text {innerText: ""}
no text found... retrying
checking for text {innerText: ""}
checking for text {innerText: "testing"}
FINISH CHECKING {innerText: "testing"}

未找到文本时的目标输出（注释掉 setTimeout）：

checking for text {innerText: ""}
no text found... retrying
checking for text {innerText: ""}
checking for text {innerText: ""}
checking for text {innerText: ""}
FINISH CHECKING {innerText: ""}

没有找到文本时的实际输出（注释掉 setTimeout）：

checking for text {innerText: ""}
no text found... retrying
checking for text {innerText: ""}
checking for text {innerText: ""}
checking for text {innerText: ""}

我尝试在 retryWhen 之后添加 catchError，希望将其添加到订阅成功处理程序中。但它仍然没有。有什么想法吗？

Answer 1

retryWhen不可能。

retryWhen 运算符 completes 在重试给定尝试后（在本例中，由 take(3) 和 delay(1000) 指定）。因此，如果在重试期间，您的 checkForText$ 源可观察对象未发出已解决的承诺或非错误值，则由 checkForText$ 和 retryWhen 组成的管道将不会发出任何内容，最终流将完成 post 重试。

在那之后就没有办法进入成功处理程序，除非你专门让 checkForText$ 在重试期间发出一些非错误值。

所以，如果您像下面这样在观察者中添加一个完整的回调，

editorOpened$.pipe( 
    switchMap(editor => 
        checkForText$.pipe(
            retryWhen(errors => {
                console.log ('no text found... retrying')
                return errors.pipe( 
                    delay(1000), 
                    take(3),
                )
            }),     
         )
     )  
).subscribe(editor => {
    console.log('FINISH CHECKING', editor)  
  }, 
  (err) => console.log('ERROR ',err), 
  () => console.log('I'm done!') //The complete handler
);

如果没有找到带有 setTimeout 注释的文本，您的情况将 return 跟随 -

checking for text {innerText: ""}
no text found... retrying
checking for text {innerText: ""}
checking for text {innerText: ""}
checking for text {innerText: ""}
I'm done!

然而，您可以使用 retry 实现此目的，但我不确定仅使用 retry.

如何引入延迟

editorOpened$
  .pipe(
    switchMap(editor =>
      checkForText$.pipe(
        retry(3),
        catchError(errors => of(editor))
      )
    )
  )
  .subscribe(
    editor => {
      console.log("FINISH CHECKING", editor);
    },
    err => console.log("ERROR ", err),
    () => console.log("I'm done!")
  );

这将产生：

checking for text {innerText: ""}
checking for text {innerText: ""}
checking for text {innerText: ""}
checking for text {innerText: ""}
FINISH CHECKING {innerText: ""}
I'm done!

Answer 2

正如上面 post 指出的那样，它 无法使用 retryWhen。但是，您 可以使用重试 来实现此目的，方法是确保您的源可观察对象处理任何延迟。

editorOpened$
  .pipe(
    mergeMap(editor =>
      checkForText$.pipe(
        retry(3),
        catchError(errors => of(editor))
      )
    )
  )
  .subscribe(
    editor => console.log("Finish", editor);,
    err => console.log("Error", err),
    _ => console.log("Complete")
  );

来源可观察

function checkforText(){
    return new Promise((resolve,reject) => {
        console.log('checking for text', editor)
        if (editor.innerText == ""){
            setTimeout(_=> reject('No text'), 500); // reject after half a second
        } else {
            resolve(editor)
        }
    })
}

var checkForText$ = defer(_=> from(checkforText()))

重试，然后忽略错误并获取源值 rxjs

Retry, then ignore error and get source value rxjs

javascript

rxjs

retrywhen