Bridgecraft (homophone for "witchcraft") is a command line tool for generating the Swift interface for ObjC bridging headers. This comes handy if you have a mixed Swift-ObjC codebase and you want to use code generation tools (e.g. Sourcery) that only support Swift.
How it works
Xcode already supports generating a Swift interface for any ObjC source file:
Unfortunately, this functionality tends to be flaky to the point that one cannot rely on it. Another disadvantage is that it is not exposed on the CLI and so it's rather difficult to use it in an automated manner.
Bridgecraft reproduces the steps needed for the interface generation with some additional safeguards to provide a reliable output, namely:
- creates a copy of the given project
- extracts the bridging header build setting for the given target
- modifies the target to include a dummy source that references the bridging header
- captures the relevant flags for compiling the dummy
- preprocesses the dummy by expanding macros and includes (this is where the Xcode command usually fails)
- taps into SourceKit and generates the Swift interface
Download the latest prebuilt binary (Bridgecraft-A.B.C.zip) from Releases. Unzip the archive and run
pod 'Bridgecraft'to your Podfile and run
pod update Bridgecraft. This will download the latest release binary and place it in your project's CocoaPods path so you can run it with
Bridgecraft.xcodeprojand build the
Bridgecraftscheme. This will produce the
Bridgecraft.appartifact in the derived data folder. The executable is under
Using the Swift package manager
In the root folder, run:
$ swift build -c release -Xswiftc -static-stdlib
This will create a
.build/releasefolder and produce the
Bridgecraft is a command-line tool without UI, so you can invoke it from the shell:
$ Bridgecraft.app/Contents/MacOS/Bridgecraft <command> ...
$ bridgecraft <command> ...
depending on which build method you used.
generate: generates the Swift interface from an ObjC bridging header
patch: injects a Swift source file into an Xcode project
For details and available options run:
$ bridgecraft --help
To build: Xcode 9.2, Swift 4
To run: macOS 10.10
Caveats and known issues
Preprocessing throws away all
NS_ASSUME_NONNULLmacros which would result in implicitly unwrapped optionals all over the place. To circumvent that, use the
--assume-nonnulloption but make sure all the referenced headers have previously been audited for nullability.
If your target platform is iOS/tvOS/watchOS, chances are the command will fail because it will try to build for the device instead of the simulator. As a workaround, specify the
--destinationoptions with the usual values, e.g.
$ bridgecraft <path_to_xcodeproj> <target_name> \ --sdk iphonesimulator \ --destination 'platform=iOS Simulator,name=iPhone 6,OS=latest'
Help us keep the lights on
0.1.0 - Feb 1, 2018
- CLI syntax: previous behavior can now be accessed via the
generatecommand; introduced new
- dependency cleanup (#12 by @4brunu)
0.0.5 - Jan 21, 2018
- option to specify output file
- SPM support
- informative head comment
- code tidying (#9 by @4brunu)
0.0.4 - Jan 19, 2018
- fixed unresolved system types
0.0.3 - Jan 17, 2018
(nothing new, just fighting with cocoapods)
0.0.2 - Jan 17, 2018
- added support for overriding SDK and destination settings of xcodebuild
- removed pod platform restriction
- using kylef/Commander for argument parsing