send synchrouns request angular 6 [closed]

问题

i want to send synchrouns request this nested for loop in angular 6. it all for loop must wait each other response. Please give some example in https://stackblitz.com

protected plateInfo(debug = true) {
      for (let i = 0; i < 8; i++) {
        for (let k = 0; k < 8; k++) {
          if (k % 2 !== 0) {
            for (let threshBlock = 21; threshBlock < 31; threshBlock++) {
              if (threshBlock % 2 !== 0) {
                for (let treshWeight = 5; treshWeight < 19; treshWeight++) {
                  if (treshWeight % 2 !== 0) {
                   this.getPLateInfo.getInfoPlate({
                      qausLast: i,
                      qausParam: k,
                      treshBlock: threshBlock,
                      treshWeight: treshWeight
                    }).subscribe(_data => {
                      this.result.push(_data)
                      _data.input1 = i
                      _data.input2 = k
                    })
                  }
                }
              }
            }
          }
        }
      }
}

回答1:

What you need is a

concatMap does not subscribe to the next observable until the previous completes,

from([your source array])
    .pipe(
        concatMap(
            (item in your array) => {
                return this.getPLateInfo.getInfoPlate(....
            }
        )
    )
    .subscribe(
        (received data from your api call) => {
            process received data here...
        }
    );

import them from:

import { from } from 'rxjs';
import { concatMap } from 'rxjs/operators';

More info on concatMap here.

EDIT:

Here is a working stackblitz

Your original "plateInfo" function will make more than 1000 api calls, I hope you know what you are doing.

Anyway, I had to limit the number of items in the array to keep stackblitz site responsive.

回答2:

Try using await/async

async getResult(): MyCustomObject {
    if (typeof this.result === 'undefined') 
    {
        // save result
        this.result = await this.service.call()
        .toPromise()
        .then(resp =>resp as MyCustomObject);//Do you own cast here

    }
    return this.result;
}

来源：https://stackoverflow.com/questions/56156313/send-synchrouns-request-angular-6

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javascript

angular

synchronization

angular6