How to make two api calls using Promise.all within Angular9?

Question

I making an api call using Promise.all as below:

    Promise.all(this.hostName.slice(0, this.Id.length).map((hostName) => {
        return this.serviceC.status(hostName)
            .then(res => {
                return new Promise((resolve, reject) => {
                    const oretry: ORInterface = {
                        oQid: res.rows[0].qid,
                        reason: this.reason
                    };
                    this.serviceB.retry(oretry).subscribe(resolve);
                });
            });
    }))
.then(() => {
        this.dialog.close();
    })
        .catch(err => {
            console.log(err);
        });

The above code is working fine. Now I want to make another api call after the successful completion of this.serviceB.retry(oretry) . The second api is this.serviceB.createDbEntry(sentry) and sentry looks as below:

                    const sretry: SDInterface = {
                        hostName,
                        Id: this.Id.slice(0, this.Id.length),
                        reason: this.reason
                    };

And, I am doing it as below

    Promise.all(this.hostName.slice(0, this.Id.length).map((hostName) => {
        return this.serviceC.status(hostName)
            .then(res => {
                return new Promise((resolve, reject) => {
                    const oretry: ORInterface = {
                        oQid: res.rows[0].qid,
                        reason: this.reason
                    };
                    const sretry: SDInterface = {
                        hostName,
                        Id: this.Id.slice(0, this.Id.length),
                        reason: this.reason
                    };
                    this.serviceB.retry(oretry).subscribe(resolve);
                    this.serviceB.createDbEntry(sentry).subscribe(resolve);
                });
            });
    }))
.then(() => {
        this.dialog.close();
    })
        .catch(err => {
            console.log(err);
        });

The above code is giving an error:

error: "SequelizeValidationError: string violation: Id cannot be an array or an object"

It is looks like it is not calling the second api for every Id

Answer 1

promise.all takes input in an array and gives response in an array,

Create 2 functions each with your asynchronous logic returning a promise,

Say funcA and funcB, then use below to invoke them parellely

Promise.all([funcA(this.hostName), funcB(this.id)])
    .then(respones => {
        console.log(responses[0]); //return value for funcA
        console.log(responses[1]); //return value for funcB
    })
    .catch(err => console.log(err));

I am assuming your logic of functions are correct, I just copy-pasted from your question and gave them structure

const funcA = (hostName) => {
hostName.slice(0, this.Id.length).map((hostName) => {
    return this.serviceC.status(hostName)
        .then(res => {
            return new Promise((resolve, reject) => {
                const oretry: ORInterface = {
                    oQid: res.rows[0].qid,
                    reason: this.reason
                };
                this.serviceB.retry(oretry).subscribe(resolve);
            });
        });
    });
}


const funcB = (Id) => {
Id.slice(0, this.Id.length).map(id => {
                return new Promise((resolve, reject) => {
                    const sretry: SDInterface = {
                        hostName,
                        Id: id,
                        reason: this.reason
                    };

                    this.serviceB.createDbEntry(sentry).subscribe(resolve);
                });
            })
}

Answer 2

You may want to take a look a forkJoin

import { Observable, forkJoin } from 'rxjs';

And then

ngOnInit() {
    let one = this.http.get('some/api/1') //some observable;
    let two = this.http.get('some/api/2') // another observable;

    forkJoin([one, tow]).subscribe(response => {
     // results[0] is our one call
     // results[1] is our second call
     let var1 = response[1];
     let var2 = response[0];
    }/*, error => { in case error handler } */); 
}

Answer 3

Wouldn't it be better to use Promise.all() once more?

Promise.all(this.hostName.slice(0, this.Id.length).map((hostName) => {
    return this.serviceC.status(hostName)
        .then(res => {
            return new Promise((resolve, reject) => {
                const oretry: ORInterface = {
                    oQid: res.rows[0].qid,
                    reason: this.reason
                };
                this.serviceB.retry(oretry).subscribe(resolve);
            });
        })
        .then(() => {
            return Promise.all(this.Id.slice(0, this.Id.length).map(id => {
                return new Promise((resolve, reject) => {
                    const sretry: SDInterface = {
                        hostName,
                        Id: id,
                        reason: this.reason
                    };

                    this.serviceB.createDbEntry(sentry).subscribe(resolve);
                });
            })
        });
}))
    .then(() => {
        this.dialog.close();
    })
    .catch(err => {
        console.log(err);
    });

And using toPromise() will make the code more concise.

Promise.all(this.hostName.slice(0, this.Id.length).map((hostName) => {
    return this.serviceC.status(hostName)
        .then(res => {
            const oretry: ORInterface = {
                oQid: res.rows[0].qid,
                reason: this.reason
            };
            return this.serviceB.retry(oretry).toPromise();
        })
        .then(() => {
            return Promise.all(this.Id.slice(0, this.Id.length).map(id => {
                const sretry: SDInterface = {
                    hostName,
                    Id: id,
                    reason: this.reason
                };

                this.serviceB.createDbEntry(sentry).toPromise();
            })
        });
}))
    .then(() => {
        this.dialog.close();
    })
    .catch(err => {
        console.log(err);
    });

Answer 4

Use combineLatest, in Angular we use RxJs not promises.

combineLatest(
  [this.http.get('call1'), this.http.get('call2')]
).subscribe(([result1, result2]) => {
  // do stuff with result1 and result2
});