Xcode playgrounds are a delightful way to explore the Swift language -- once you get them set up.

To use this as a starting point, fork and clone the repo, cd into the directory, and:

rvm use ruby-2.2.4
gem install cocoapods
pod install

Then open the FirebasePlayground.xcworkspace and type code into experiment.playground file and it will automatically compile and execute, displaying results in the right-side panel.

It's a bit tricky to figure out how to use CocoaPods with Playgrounds, but the actual steps are straightforward:

Here are the steps to re-create this repo, using Swift 2, Xcode 7.2, OSX 10.10.5 (Yosemite):

note: cocoapods 0.39.0 has issue with Ruby 2.3 — likely fixed in the 1.0 beta, but I stuck with older ruby and released CocoaPod for this exercise.

rvm use ruby-2.2.4
gem install cocoapods

Make a new Xcode project with File > New > Project...

then add a new Empty file to your project called Podfile by selecting from the menu File > New > File… then Other > Empty)

with the following contents:

platform :ios, '8.1'
xcodeproj 'FirebasePlayground'

use_frameworks!
target :FirebasePlayground, exclusive: true do
  pod 'Firebase'
end

back on the command-line:

pod install

This creates a new Xcode workspace, so we need to close the project in Xcode, then re-open Xcode with the file named something ending in .xcworkspace.

This new workspace should have both the original project and a new one called Pods. Now we can create the Playground, by selecting the menu: File > New > Playground… Then we save it in the root of our project directory, then add it to the project with the menu: File > Add Files To “ParsePlayground”

Now this code should compile:

import Firebase
import XCPlayground
XCPlaygroundPage.currentPage.needsIndefiniteExecution = true

We want to set needsIndefiniteExecution so that async commands will work.