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Bridgecraft
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
Installation
-
Binary distribution
Download the latest prebuilt binary (Bridgecraft-A.B.C.zip) from Releases. Unzip the archive and run
bin/bridgecraft
. -
Cocoapods
Add
pod 'Bridgecraft'
to your Podfile and runpod update Bridgecraft
. This will download the latest release binary and place it in your project's CocoaPods path so you can run it with$PODS_ROOT/Bridgecraft/bin/bridgecraft
-
Manual build
-
Using Xcode
Open
Bridgecraft.xcodeproj
and build theBridgecraft
scheme. This will produce theBridgecraft.app
artifact in the derived data folder. The executable is underBridgecraft.app/Contents/MacOS/Bridgecraft
-
Using the Swift package manager
In the root folder, run:
$ swift build -c release -Xswiftc -static-stdlib
This will create a
.build/release
folder and produce thebridgecraft
executable.
-
Usage
Bridgecraft is a command-line tool without UI, so you can invoke it from the shell:
$ Bridgecraft.app/Contents/MacOS/Bridgecraft <command> ...
or
$ bridgecraft <command> ...
depending on which build method you used.
Available commands:
generate
: generates the Swift interface from an ObjC bridging headerpatch
: injects a Swift source file into an Xcode project
For details and available options run:
$ bridgecraft --help
Requirements
To build: Xcode 10, Swift 4.2<br/> To run: macOS 10.10
Caveats and known issues
-
Preprocessing throws away all
NS_ASSUME_NONNULL
macros which would result in implicitly unwrapped optionals all over the place. To circumvent that, use the--assume-nonnull
option 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
-configuration
,-sdk
,-destination
or any other options that you want to send to the xcodebuild with the usual values, e.g.$ bridgecraft generate <path_to_xcodeproj> <target_name> -- \ -configuration Debug \ -sdk iphonesimulator \ -destination 'platform=iOS Simulator,name=iPhone 6,OS=latest'
License
MIT