Observable Finally on Subscribe

The current "pipable" variant of this operator is called finalize() (since RxJS 6). The older and now deprecated "patch" operator was called finally() (until RxJS 5.5).

I think finalize() operator is actually correct. You say:

do that logic only when I subscribe, and after the stream has ended

which is not a problem I think. You can have a single source and use finalize() before subscribing to it if you want. This way you're not required to always use finalize():

let source = new Observable(observer => {  observer.next(1);  observer.error('error message');  observer.next(3);  observer.complete();}).pipe(  publish(),);source.pipe(  finalize(() => console.log('Finally callback')),).subscribe(  value => console.log('#1 Next:', value),  error => console.log('#1 Error:', error),  () => console.log('#1 Complete'));source.subscribe(  value => console.log('#2 Next:', value),  error => console.log('#2 Error:', error),  () => console.log('#2 Complete'));source.connect();

This prints to console:

#1 Next: 1#2 Next: 1#1 Error: error messageFinally callback#2 Error: error message

Jan 2019: Updated for RxJS 6

The only thing which worked for me is this

fetchData()  .subscribe(    (data) => {       //Called when success     },    (error) => {       //Called when error    }  ).add(() => {       //Called when operation is complete (both success and error)  });

I'm now using RxJS 5.5.7 in an Angular application and using finalize operator has a weird behavior for my use case since is fired before success or error callbacks.

Simple example:

// Simulate an AJAX callback...of(null)  .pipe(    delay(2000),    finalize(() => {      // Do some work after complete...      console.log('Finalize method executed before "Data available" (or error thrown)');    })  )  .subscribe(      response => {        console.log('Data available.');      },      err => {        console.error(err);      }  );

I have had to use the add medhod in the subscription to accomplish what I want. Basically a finally callback after the success or error callbacks are done. Like a try..catch..finally block or Promise.finally method.

Simple example:

// Simulate an AJAX callback...of(null)  .pipe(    delay(2000)  )  .subscribe(      response => {        console.log('Data available.');      },      err => {        console.error(err);      }  )  .add(() => {    // Do some work after complete...    console.log('At this point the success or error callbacks has been completed.');  });