CODEWITHSUNDEEP
angularrxjs
Nastaran Heydari
Nastaran Heydari

Reputation: 165

How to modify Observable values with rxjs operators?

I have an angular app and in one of the components I'm getting user's notifications(Emails) via a service. the service returns an array of Objects and in each object there's information of an email like subject , userid of the sender, etc. the structure of array of email object is like this:

[{
  UserId:"...",

  Notification:{
     Subject:null,
     Body:"<div>...</div>",
     .
     .
     .
  },
  .
  .
  .
},
.
.
.]

some emails don't have subject and the value of Subject property is null in the object. I want to set a value for emails with Subject:null.

this.notifService.getAllNotificationsForCurrentUser(userId)
.pipe(
    map(emails => {
       emails.map(email=>{
         if(email.Notification.Subject === null){
            email.Notification.Subject = "(No Subject)";
         }
       })
    }
)
.subscribe(
    result=> this.messages = result
);

I used map operator and it doesn't work. and it has some errors:

Cannot read property 'Notification' of undefined

how can I fix it?

Upvotes: 0

Views: 3341

Answers (2)

sabithpocker
sabithpocker

Reputation: 15566

If this is only for display purposes, you should just do

{{email.Notification.Subject || '(No Subject)'}}

If not, go for mapping the array.

Upvotes: 1

jo_va
jo_va

Reputation: 13963

Use the rxjs map operator with Array.prototype.map().

  1. The first map allows you to modify the array of emails as if flows down the stream. It maps over the stream elements, each element is an array of emails.

  2. The second map changes the array of emails to set the empty subject fields to no subject. It maps over the emails array, each element is an email.

import { map } from 'rxjs/operators';

this.notifService.getAllNotificationsForCurrentUser(userId).pipe(
    map(emails => {
        return emails.map(email => ({
            ...email,
            Notification: {
                ...Notification,
                Subject: email.subject ? email.subject : 'no subject'
            }
        }));
    })
).subscribe(
    result=> this.messages = result
);

Upvotes: 3

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