# Problem with Observable's expand function

**URL:** <https://forums.fusetools.com/t/problem-with-observables-expand-function/892>\
**Category:** Bug Reports\
**Created:** [April 7, 2016, 10:51am UTC](https://forums.fusetools.com/t/problem-with-observables-expand-function/892 "2016-04-07T10:51:26Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Thomas](https://yyz1.discourse-cdn.com/flex035/user_avatar/forums.fusetools.com/thomas/32/97_2.png) [@Thomas](https://forums.fusetools.com/u/Thomas)\
**Post date:** [April 7, 2016, 10:51am UTC](https://forums.fusetools.com/t/problem-with-observables-expand-function/892/1 "2016-04-07T10:51:26Z")

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Hi guys, i tried to use the expand() function on Observable object, but it returned always an empty Observable.

This is my easy code:

```auto
list_transaction = Observable ([1,2,3]);
list_transaction2 = Observable ([1,2,3]).expand();

```

In the log :

```auto
{"_subscribers":[],"_isLeaf":true,"_values":[[1,2,3]]}
{"_subscribers":[],"_isLeaf":false,"_values":[]}

```

This is a common problem?

Thanks in advance ! Bye!

---

<div class="post-metadata">

**Author:** ![Remi\_Pedersen](https://yyz1.discourse-cdn.com/flex035/user_avatar/forums.fusetools.com/remi_pedersen/32/432_2.png) [@Remi\_Pedersen](https://forums.fusetools.com/u/Remi_Pedersen)\
**Post date:** [April 7, 2016, 11:37am UTC](https://forums.fusetools.com/t/problem-with-observables-expand-function/892/2 "2016-04-07T11:37:48Z")

</div>

This is probably because the reactive operator isn’t evaluated unless the resulting value is consumed somewhere in the UI.

In other words, if your UX actually tries to use list\_transaction2 (either directly or through a dependency chain of observables) then it’ll behave exactly as expected.

You can read a bit more about it [here](https://www.fusetools.com/learn/fusejs#reactive-operators)