How can I use Swift REPL with iOS SDK

Question

Can I run Swift REPL with iOS SDK?

I want to import and use UIKit in REPL, but no success.

$ xcrun --sdk iphonesimulator8.1 --show-sdk-p         


        

Answer 1

The Swift REPL currently does not support iOS device or iOS simulator.

Answer 2

You may achieve it by running repl from lldb, which attached to iOS application process (of your Xcode project).

1. Build project in Xcode, or:

   $ xcrun xcodebuild -configuration Debug -destination 'platform=iOS Simulator,name=iPhone 7,OS=10.3' clean build
   

2. Start standalone lldb for your iOS project:

   $ xcrun lldb -- $DerivedData/$AppName/Build/Products/Debug-iphonesimulator/$AppName.app
   (lldb) process attach --name '$AppName' --waitfor
   

   You may find useful platform select ios-simulator and platform connect $UDID commands here.

3. Run your iOS application in iOS simulator from Xcode

   • Or from command line:

     1. Boot simulator

        • From instruments:

          $ xcrun instruments -w "`xcrun instruments -s | grep 'iPhone 7 (10.3)' | head -1`"
          

        • Or as an application:

          $ open -a "Simulator" --args -CurrentDeviceUDID "`xcrun instruments -s | grep 'iPhone 7 (10.3)' | head -1 | sed -E -e 's/[^][]*\[([^][]*)\][^][]*/\1/g'`"
          

     2. Install the application on simulator, and launch it:

        $ xcrun simctl install booted $DerivedData/$AppName/Build/Products/Debug-iphonesimulator/$AppName.app
        $ xcrun simctl launch booted $AppBundleID
        

        Also, you can even use xcrun simctl launch --wait-for-debugger and start lldb later.

   • Or with ios-sim:

     1. Optionally boot simulator & install the application:

        $ ios-sim start --devicetypeid 'iPhone-7, 10.3'
        $ ios-sim install --devicetypeid 'iPhone-7, 10.3' $DerivedData/$AppName/Build/Products/Debug-iphonesimulator/$AppName.app
        

     2. Launch it:

        $ ios-sim launch --devicetypeid 'iPhone-7, 10.3' $DerivedData/$AppName/Build/Products/Debug-iphonesimulator/$AppName.app
        

4. Attach to process in iOS simulator in lldb:

   (lldb) continue
   (lldb) process interrupt
   

5. Run swift repl.

   (lldb) repl
    1> import UIKit
    2> 
   

Furthermore, as opposed to swift repl in Xcode debug terminal emulator, here we have working source autocompletion and command history navigation.