Getting playgrounds working in a project in xcode

gistfile1.txt

1. Create a new xcode project
  - You can skip this if you're adding the playground to an existing project
2. File > Save as workspace - save workspace in project folder
  - You can skip this if you're adding the playground to an existing workspace
3. File > Playground - create new playground in project folder
4. Drag playground in at the _workspace_ level (root item, i.e. _not_ under the project)
5. Add a new Framework to your project (I usually name mine something like 'PlaygroundKit')
  - You don't need to include tests
  - Choose 'None' for Enbed in Application
6. Make all project files you want to be accessible to the playground are members of the new target 
  - this includes any new files you add
7. Build the new target 
  - You need to do this each time you make changes so they are available to the playground
8. `@testable import <PlaygroundTarget>` in playground and go nuts
  - `@testable` can be omitted if everything you want available to the playground is explicitly `public`

NOTE: If you have any Cocoapods, make sure you add a target entry for <PlaygroundTarget> so they get access to the pods

Having said that - I'm almost certain that you can add a playground to a project in xcode10 and it 'just works' - I could have sworn I saw something on one of the talks at WWDC about this...