# Chapter 10: challenge 1 '.do'?

**URL:** <https://forums.kodeco.com/t/chapter-10-challenge-1-do/78660>\
**Category:** RxSwift\
**Created:** [August 9, 2019, 10:43am UTC](https://forums.kodeco.com/t/chapter-10-challenge-1-do/78660 "2019-08-09T10:43:01Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![jawzapps](https://assets.chunter.kodeco.com/user_avatar/forums.kodeco.com/jawzapps/32/108006_2.png) [@jawzapps](https://forums.kodeco.com/u/jawzapps)\
**Post date:** [August 9, 2019, 10:43am UTC](https://forums.kodeco.com/t/chapter-10-challenge-1-do/78660/1 "2019-08-09T10:43:01Z")

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OK, so I’ve been scratching my head over the first challenge in chapter 10 and finally had to look at the solution, which involves a “.do” operator. A what now? I’ve searched back through the book and it looks like “.do” hasn’t been introduced so far, so feeling a little “erm, oh” about this particular challenge. Did I miss something?

What does ‘.do’ do? And how are we supposed to have come up with that solution if we haven’t heard of it yet?

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**Author:** ![shogunkaramazov](https://assets.chunter.kodeco.com/user_avatar/forums.kodeco.com/shogunkaramazov/32/108826_2.png) [@shogunkaramazov](https://forums.kodeco.com/u/shogunkaramazov)\
**Post date:** [September 5, 2019, 10:16pm UTC](https://forums.kodeco.com/t/chapter-10-challenge-1-do/78660/2 "2019-09-05T22:16:49Z")

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@jawzapps Do you still have issues with this?

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**Author:** ![system](https://s3.amazonaws.com/cdn.raywenderlich.com/community/forum-assets/noun-game-ghost-878668.png) [@system](https://forums.kodeco.com/u/system)\
**Post date:** [January 23, 2020, 2:43am UTC](https://forums.kodeco.com/t/chapter-10-challenge-1-do/78660/3 "2020-01-23T02:43:04Z")

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Closed on January 23, 2020, 2:43am UTC

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