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Yes, HotReloading for Swift, Objective-C & C++!

This project is the InjectionIII app for live code updates available as a Swift Package. i.e.:


Note: you should only add the HotReloading product to your target.

Then, you can inject function implementations without having to rebuild your app... Icon

To try out an example project that is already set-up, clone this fork of SwiftUI-Kit.

To use on your project, add this repo as a Swift Package and add "Other Linker Flags": -Xlinker -interposable. You no longer need to add a "Run Script" build phase. If want to inject on a device, see the notes below on how to configure the InjectionIII app. Note however, on an M1/M2 Mac this project only works with an iOS/tvOS 14 or later simulator. Also, due to a quirk of how Xcode how enables a DEBUG build of Swift Packages, your "configuration" needs to contain the string "Debug".

Remember not to release your app with this package configured.

You should see a message that the app is watching for source file changes in your home directory. You can change this scope by adding comma separated list in the environment variable INJECTION_DIRECTORIES. Should you want to connect to the when using the simulator, add the environment variable INJECTION_DAEMON to your scheme.

Consult the README of the InjectionIII project for more information in particular how to use it to inject SwiftUI using the HotSwiftUI protocol extension.

HotReloading using VSCode

It's possible to use HotReloading from inside the VSCode editor and realise a form of "VScode Previews". Consult this project for the setup required.

Device Injection

This version of the HotReloading project and it's dependencies now support injection on a real iOS or tvOS device.

Device injection now connects to the (github release 4.6.0 or above) and requires you type the following commands into a Terminal then restart the app to opt into receiving remote connections from a device:

$ rm ~/Library/Containers/com.johnholdsworth.InjectionIII/Data/Library/Preferences/com.johnholdsworth.InjectionIII.plist
$ defaults write com.johnholdsworth.InjectionIII deviceUnlock any

Note, if you've used the App Store version of InjectionIII in the past, the binary releases have a different preferences file and the two can get confused and prevent writing this preference from taking effect. This is why the first rm command above can be necessary. If your device doesn't connect check the app is listening on port 8899:

% netstat -an | grep LIST | grep 88
tcp4       0      0         *.*                    LISTEN
tcp4       0      0  *.8899                 *.*                    LISTEN

If your device still doesn't connect either add an INJECTION_HOST environment variable to your scheme containg the WiFi IP address of the host you're running the on or clone this project and code your mac's IP address into the hostname variable in Package.swift. Then, drag the clone onto your project to have it take the place of the configured Swift Package as outlined in these instructions.

Note: as the HotReloading package needs to connect a network socket to your Mac to receive commands and new versions of code, expect a message the first time you run your app after adding the package asking you to "Trust" that your app should be allowed to do this. Likewise, at the Mac end (as the InjectionIII app needs to open a network port to accept this connection) you may be prompted for permission if you have the macOS firewall turned on.

For SwiftUI you can force screen updates by following the conventions outlined in the HotSwiftUI project then you can experience something like "Xcode Previews", except for a fully functional app on an actual device!

Vapor injection

To use injection with Vapor web server, it is now possible to just download the and add the following line to be called as the server configures (when running Vapor from inside Xcode):

    #if DEBUG && os(macOS)
    Bundle(path: "/Applications/")?.load()

It will also be necessary to add the following argument to your targets:

    linkerSettings: [.unsafeFlags(["-Xlinker", "-interposable"],
            .when(platforms: [.macOS], configuration: .debug))]

As an alternative, you can add this Swift package as a dependency to Vapor's Package.swift of the "App" target.

Thanks to...

The App Tracing functionality uses the OliverLetterer/imp_implementationForwardingToSelector trampoline implementation via the SwiftTrace project under an MIT license.

SwiftTrace uses the very handy as an alternative to the dyld_dynamic_interpose dynamic loader private api. See the project source and header file included in the framework for licensing details.

The "Remote" server in this project which allows you to capture videos from your device includes code adapted from acj/TimeLapseBuilder-Swift

This release includes a very slightly modified version of the excellent canviz library to render "dot" files in an HTML canvas which is subject to an MIT license. The changes are to pass through the ID of the node to the node label tag (line 212), to reverse the rendering of nodes and the lines linking them (line 406) and to store edge paths so they can be coloured (line 66 and 303) in "canviz-0.1/canviz.js".

It also includes CodeMirror JavaScript editor for the code to be evaluated in the Xprobe browser under an MIT license.

$Date: 2023/09/18 $