Building iOS apps with Genero

Genero provides a command-line tool to build applications for iOS devices.


Genero mobile apps for iOS are distributed as IPA packages, like any other iOS app. Genero provides a command line tool to build the .ipa package for your mobile application, or the .app directory for simulators.

Note: This documentation section implies that you are familiar with iOS app programming concepts and requirements. In order to build your apps, you must have an Apple® developer account, as well as certificates and provisioning profiles to deploy your apps. For more details, visit the Apple developer site.


Before starting the command line tool to build or deploy the app, fulfill the following prerequisites:
  1. The Genero BDL development environment (FGLDIR) must be installed on the Mac computer to compile your program files.
  2. The GMI archive (and gmibuildtool) must be installed and available.

    The GMI archive is provided as a ZIP archive (fjs-fglgmi-*.zip). Extract the archive into FGLDIR.

    Warning: If the GMI archive is not extracted into FGLDIR, the Xcode® project of the $FGLDIR/demo/MobileDemo/userfrontcall demo does not work.
    For test purposes, the GMI zip archive can be installed elsewhere in a location of your choice. You may choose to do this to resolve problems resulting from several GMI versions. If you install elsewhere, define an environment variable GMIDIR with the install location and add $GMIDIR/bin to the path.
    Note: The GMI buildtool does not need GMIDIR; However, all the supplied GMI demos need GMIDIR in the Makefiles.
    Check that the gmibuildtool command is available (add GMI-install-dir/bin to PATH for convenience).
    Important: When re-installing a new GMI archive, remove all "build" directories created by the gmibuildtool.
  3. Get an Apple developer account, device identifiers (UDID) and corresponding identifiers to sign your iOS app (certificate, bundle id, provisioning profile).
    Important: The UDID is the identifier of your physical device, it can be found with the xcrun xctrace list devices Xcode command when the device is plugged to the Mac. When deploying on a physical device, make sure that the UDID of the device is listed in the Apple Developer account that is used to generate the provisioning profiles.
  4. Xcode must be installed on your macOS® computer (utilities from Xcode toolchain are required).
    Note: Make sure that the installed Xcode version supports the iOS versions of your mobile devices. As a general rule, update the Xcode and iOS to the latest versions.
  5. iOS app resources such as icons and launch images (in all required sizes).

Finding the UDID of the plugged device

In order to find the UDID of the device plugged to your Mac, execute the xcrun xctrace list devices Xcode command, and identify the line describing your physical device:
$ xcrun xctrace list devices
== Devices ==
== Simulators ==
Apple TV 4K (2nd generation) (14.5) (XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX)
Apple TV 4K (at 1080p) (2nd generation) (14.5) (XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX)
ipad (8th generation) (14.5) (XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX)

In the above output, the UDID of the iPod® is 78b7452fa9462c98c3bc7047da344314fd032004.

Environment settings

Before starting the command-line buildtool, make sure that Xcode tools are available. Try xcodebuild -version from the command line:
$ xcodebuild -version
Xcode 11.3.1
Build version 11C504

The gmibuildtool

The gmibuildtool command line tool can build IPA packages of iOS apps written in Genero.

In order to identify the exact product version number of each GMI component, use the --version option of the gmibuildtool:
$ gmibuildtool --version
GMI version:1.40.04
VM  version:3.20.05
GWS version:3.20.05
Cordova ver:gm_1.30.14

Manage GMI plugins

In order to get the list of plugins installed in the GMI environment, use the --list-plugins option:

$ gmibuildtool --list-plugins

To install additional plugins in the GMI installation directory, use the --install-plugins option, for example:

gmibuildtool --install-plugins path-to-plugin-sources

For more usage examples, see Cordova plugins.

Creating the GMI front-end for development purpose

A self-made GMI front-end can be created with the gmibuildtool command. For more details, see Mobile development mode.

Specifying the target to build and deploy the iOS app

The gmibuildtool command can build and install iOS apps for the simulator or for physical devices.

The build and/or install action is controlled by the --device option:

  • By default, when not specifying the --device option, a directory is created for the simulator.
  • When specifying the --device booted option, the directory is created and the app is installed on the booted simulator.
  • When specifying the --device phone option, the directory and .ipa file are created.
  • When specifying the --device physical-device-name option (with a real physical device name plugged on your Mac), the directory and .ipa file are created and the app is installed on the device.

By default, the generated directory and .ipa archive can be found in $PWD/build sub-directories; however, you can specify the destination IPA file with the --output option.

Specifying the GBC to be used

Use the --gbc option, to specify which GBC has to be bundled in the iOS app package:
gmibuildtool ... --gbc gbc-archive ...

The gbc-archive parameter is the ZIP archive of the GBC front-end, to be created as described in the Create a runtime zip topic in the Genero Browser Client User Guide.

The parameter for the --gbc option can also be a regular (unzipped) GBC directory.

If the --gbc option is not used, gmibuildtool will use the GBC found in FGLGBCDIR, and if that environment variable is not defined, it defaults to FGLDIR/web_utilities/gbc/gbc.

Elements used to build the iOS app

The gmibuildtool command builds the iOS app package from the following:
  • The GMI binary archive, containing the GMI front-end and the FGLGWS runtime system library,
    Note: These files are provided in the fjs-fglgmi-*.zip archive.
    Important: When re-installing a new GMI archive, remove all "build" directories created by the gmibuildtool.
  • The GBC to be used (--gbc option),
  • The compiled application program and resource files (.42m, .42f, etc),
    Note: The application program files must include a main.42m or main.42r module.
  • The display name of the app (--app-name option),
  • The version of the app (--app-version option),
  • The debug or release mode (--mode option),
  • The certificate (to sign the app) (--certificate option),
  • The bundle Identifier (--bundle-id option),
  • The app provisioning profile (.mobileprovision file) (--provisioning option),
  • iOS app specific resources:
    • App icons (--icons option),
    • Launch images (--launch-images option) or launch storyboard file (--storyboard option).

For a complete description of command options, see gmibuildtool.

Default build directory structure

For convenience, the buildtool supports a default directory structure to find all files required to build the app:

|-- main.42m and other program files, as described in Directory structure for GMI apps
|-- gmi
|   |
|   |-- Info.plist
|   |
|   |-- LaunchScreen.storyboard  or  (default launch images)
|   |                              -- Default@2x.png
|   |                              -- Default-568h@2x.png
|   |                              -- Default-Landscape.png
|   |                              -- Default-Landscape-667h@2x.png
|   |                              -- Default-Landscape-736h@3x.png
|   |                              -- Default-Landscape@2x.png
|   |                              -- Default-Portrait.png
|   |                              -- Default-Portrait-736h@3x.png
|   |                              -- Default-Portrait-667h@2x.png
|   |                              -- Default-Portrait@2x.png
|   |   ...
|   |-- icon_29x29.png
|   |-- icon_40x40.png
|   |-- icon_57x57.png
|   |-- icon_58x58.png
|   |-- icon_72x72.png
|   |-- icon_76x76.png
|   |-- icon_80x80.png
|   |-- icon_120x120.png
|   |-- icon_152x152.png
|   |   ...
In the above directory structure:
  1. top-dir is the top directory of the default structure. It will typically hold your application program files. A different program files directory can be specified with the --program-files option.
  2. top-dir/gmi is the default directory containing the app resource files such as icons:
    1. Info.plist is the Information Property List File that will be used to build the app. Some properties will be overwritten by gmibuildtool options like --app-name and --app-version.
    2. Provide either a launch screen storyboard or default launch images:
      • LaunchScreen.storyboard is the default storyboard file for the app launch screen. This file can be specified with the gmibuildtool --storyboard option.
      • Default-*.png are the app launch image files. The directory to find launch images can be specified with the gmibuildtool --launch-images option.
    3. icon_*.png are the app icon files. The directory to find icons can be specified with the gmibuildtool --icons option.

Debug and release versions

iOS apps can be generated in a debug or release version. Release version are prepared for distribution on the App Store, while debug versions are used in development.

In debug mode, the app installed on the device can listen on the debug TCP port to allow fgldb -m connections, after enabling the debug port in the app settings.

Debug or release mode must be specified in the command line with the --mode debug or --mode release option. Additionally, if you want to deploy on a physical device, you need to use a provisioning profile corresponding to the debug or release mode:

  • In debug mode, the certificate must be a development certificate.
  • In release mode, the certificate must be a distribution certificate.

Defining the app version and build number

Apple distinguishes the app version number of a bundle (visible to the end user), from the build version number of a bundle (called a release version number in Apple docs).

You specify the app version number with the --app-version option of the gmibuildtool command. This option sets the CFBundleVersion property of the Info.plist file), and must match the version specified in iTunes® Connect.

In order to distinguish multiple builds (Apple's term is "releases") of the same app version number, define the build version number of your app with the --build-number option. This option sets the CFBundleShortVersionString property of the Info.plist file. For a given app version, you need to increase this build number, to be able to upload a new binary on iTunes Connect.

Note: If you do not specify the --build-number option, the build version number defaults to the app version specified with the --app-version option.

Defining app properties in the ./gmi/Info.plist file

iOS app are created with a set of properties that are essential configuration information for a bundled executable. These properties are defined in the "Information Property List File", an XML formatted file named Info.plist by convention.

Most important Info.plist properties are defined with gmibuildtool options such as --app-name and --app-version. However, you may need to define other properties that are out of the scope of the buildtool. For example: background modes, device capabilities, screen orientations, permanent wifi, and so on.

In order to define specific app properties, create an Info.plist file in the top-dir/gmi directory before executing the gmibuildtool. Properties covered by the buildtool will be overwritten, while any other property defined in the top-dir/gmi/Info.plist file will be left untouched.

For more details about the Info.plist file structure, see Apple developer site page about Information Property List File.

Building an iOS app with gmibuildtool

Follow the next steps to setup a GMI app build directory in order to create an iOS app, based on the default directory structure:

  1. Create the root distribution directory (top-dir)
  2. Copy compiled program files (.42m, .42f, fglprofile, application images, web component files, etc) under top-dir.
  3. Copy the default English .42s compiled string resource file under top-dir.
  4. Create non-English langage directories (fr, ge, ...) under top-dir and copie the corresponding .42s files.
  5. Copy default application data files (database file for ex) under top-dir.
  6. Create the top-dir/gmi directory.
  7. Copy iOS app resources (icons, launch screen, storyboard) under top-dir/gmi.
  8. If needed, create an top-dir/gmi/Info.plist file, to define specific iOS app properties.
Once the build directory is prepared, issue the following commands:
$ cd top-dir
$ gmibuildtool \
    --output myapp.ipa \
    --app-name "My App" \
    --app-version "v3.1.6" \
    --bundle-id "com.example.mycompany.myapp" \
    --mode release \
    --certificate "iPhone Developer" \
    --provisioning "~/Downloads/myapp.mobileprovision" \
    --device phone

Building a GMI app with C extensions or custom front calls

In order to create an iOS app using C extensions written in Objective-C as in Implementing C-Extensions for GMI, proceed as follows (the same technique can be used to build apps that include custom front calls):

  1. Build a static library from your Objective-C sources, by using the staticlib target of the $GMIDIR/lib/Makefile-gmi generic makefile (specify the library file name with the USER_LIBNAME variable). The staticlib makefile target will produce a .a library file, by using all .m and .c files found in the current directory. For example:
    $ make -f $GMIDIR/lib/Makefile-gmi USER_LIBNAME=mylib.a staticlib
  2. When building the app, specify the additional libraries with the --extension-libs option. For example:
    $ gmibuildtool ... --extension-libs "-lz libBPush.a mylib.a" ...

Regardless of whether the --extension-libs option is used, the gmibuildtool looks to see if ./gmi/*.a exists. If they exist, it adds these static libs to the link list.

If a file called ./gmi/ exists, this file is read by gmibuildtool to set additional link flags. For example:

#set LINK_FLAGS to add additional system libs or frameworks
LINK_FLAGS="-bz2 -framework MapKit"

In most cases the *.a files will be sufficient, for system frameworks like MapKit, as long as the following hint is specified in your .m source file:

/* this avoids using -framework MapKit and instructs the linker to link with MapKit*/
@ import MapKit;

Only pure C libs such as libbz2.a actually need the file, if no --extension-libs option is used and one of the static extension libs needs a system C library.

For complete examples, see $GMIDIR/demo/MobileDemo/userextension and $GMIDIR/demo/MobileDemo/userfrontcall