Nsryjdtyk

i have my code with ionic 3 angular 5 working as below

getUser(uid:string){

    console.log('start of getUser with uid:' + uid)

    return new Promise((resolve, reject) =>

      {

        this.db.object("/users/" + uid).snapshotChanges().map(

          (snapshot) => {return snapshot.payload.val()}

        ).subscribe(

          res => {

            console.log('response:' + res)

            resolve(res)

          },

          err => {

            console.log(err)

            reject(err)

          }

        )

      })

  }

however, with ionic 4 .map does not work any more. how do i convert this code?

Just like you can see here

Starting in version 5.5 we have shipped "pipeable operators", which
can be accessed in rxjs/operators (notice the pluralized "operators").
These are meant to be a better approach for pulling in just the
operators you need than the "patch" operators found in rxjs-compat
package.

NOTE: Using rxjs or rxjs/operators without making changes to your
build process can result in larger bundles.

So now you can use map() like this:

// RxJS

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



// ...



getUser(uid:string){

    console.log('start of getUser with uid:' + uid)

    return new Promise((resolve, reject) => {

        this.db.object("/users/" + uid)

            .snapshotChanges()

            .pipe(

                map((snapshot) => {

                    return snapshot.payload.val();

                })

            )

            .subscribe(

                res => {

                    console.log('response:' + res)

                    resolve(res)

                },

                err => {

                    console.log(err)

                    reject(err)

                }

            )

    })

}

Not related to the question itself but just in case, if you want your getUser() method to return a promise, you can use RXJS operators as well (instead of creating and resolving a promise), like this:

// RxJS

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

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



// ...



public getUser(uid: string): Promise<any> {

    console.log('start of getUser with uid:' + uid)



    return this.db

        .object("/users/" + uid)

        .snapshotChanges()

        .pipe(

            map((snapshot) => {

                return snapshot.payload.val();

            }),

            tap((response) => {

                console.log('response:' + response);

            })

        )

        .toPromise()

}