InjectionIII 4+

Quite simply, InjectionIII adds "Hot Reloading" capability to your iOS, tvOS and macOS projects written in Swift or Objective-C. This allows you to change the implementations of methods, functions and SwiftUI body properties without having to restart your app for rapid iteration over minor code changes and design.

To get up and running, install the app to /Applications and run it and it will appear on the menu bar.
Then, download the example project http://johnholdsworth.com/GettingStarted.zip, build and run it in Xcode. You’ll be promoted to select the directory containing the project file and sources to give InjectionIII access to which files have changed. Once injection has connected, when you save a file, it will be recompiled and injected into the running app, the new implementations taking place of the old. In the GettingStarted iOS app, if you edit the file DetailViewController.swift to change the string appended after the detail.description in function configureView() then save the file, you can see it take effect straight away.

InjectionIII requires a version of Xcode more recent than 10.2, installed at the standard location /Applications/Xcode.app. For a project to be injectable, you must also add "-Xlinker -interposable" to the Debug target of its "Other Linker Flags" build setting. Then, add one of the following to your app’s startup to connect to InjectionIII:

Xcode 10.2 and later:

#if DEBUG
Bundle(path: "/Applications/InjectionIII.app/Contents/Resources/iOSInjection.bundle")?.load()
//for tvOS:
Bundle(path: "/Applications/InjectionIII.app/Contents/Resources/tvOSInjection.bundle")?.load()
//Or for macOS:
Bundle(path: "/Applications/InjectionIII.app/Contents/Resources/macOSInjection.bundle")?.load()
#endif

InjectionIII is able to inject SwiftUI but requires minor code changes to "body" properties to ensure views are redrawn on injection. The easiest way to do this is using the "Prepare Project" menu item after you have selected a project and it will make the necessary changes.

If your project is organised across multiple directories, after you have selected the main project, you can add directories to be watched for file changes using the "Add Directory" menu item. This list resets when you select a new project. You'll need to turn sandboxing off to be able to use injection on a macOS application. Consult the project README on the support page for more information.