layout: documentation title: Tutorial - Build an iOS App

Tutorial - Build an iOS App

Like the Android app you built in the previous step, the iOS app is a simple mobile app that communicates with the backend server.

Here, you'll do the following:

Review the source files for the app
Create a BUILD file
Build the app for the simulator
Find the build outputs
Run/Debug the app on the simulator
Build the app for a device
Install the app on a device

Note that, unlike with the Android app, you don't have to modify your WORKSPACE file to add iOS-specific external dependencies.

If you're following the steps in this tutorial on Mac OS X, you can go ahead and build the sample iOS app as described below. If you are on Linux, skip ahead to the next step.

Review the source files

Let‘s take a look at the source files for the app. These are located in $WORKSPACE/ios-app/UrlGet. Again, you’re just looking at these files now to become familiar with the structure of the app. You don't have to edit any of the source files to complete this tutorial.

Create a BUILD file

At a command-line prompt, open your new BUILD file for editing:

$ vi $WORKSPACE/ios-app/BUILD

Add an objc_library rule

Bazel provides several build rules that you can use to build an app for the iOS platform. For this tutorial, you‘ll first use the objc_library rule to tell Bazel how to build an static library from the app source code and Xib files. Then you’ll use the objc_binary rule to tell it how to bundle the iOS application. (Note that this is a minimal use case of the Objective-C rules in Bazel. For example, you have to use the ios_application rule to build multi-architecture iOS apps.)

Add the following to your BUILD file:

objc_library(
    name = "UrlGetClasses",
    srcs = [
        "UrlGet/AppDelegate.m",
        "UrlGet/UrlGetViewController.m",
    ],
    hdrs = glob(["UrlGet/*.h"]),
    xibs = ["UrlGet/UrlGetViewController.xib"],
)

Note the name of the rule, UrlGetClasses.

Add an objc_binary rule

The objc_binary rule creates a binary to be bundled in the application.

Add the following to your BUILD file:

objc_binary(
    name = "ios-app-binary",
    srcs = [
        "UrlGet/main.m",
    ],
    deps = [
        ":UrlGetClasses",
    ],
)

Note how the deps attribute references the output of the UrlGetClasses rule you added to the BUILD file above.

Add an ios_application rule

The ios_application rule creates the bundled .ipa archive file for the application and also generates an Xcode project file.

Add the following to your BUILD file:

ios_application(
    name = "ios-app",
    binary = ":ios-app-binary",
    infoplist = "UrlGet/UrlGet-Info.plist",
)

Now, save and close the file. You can compare your BUILD file to the completed example in the master branch of the GitHub repo.

Build the app for the simulator

Make sure that your current working directory is inside your Bazel workspace:

$ cd $WORKSPACE

Now, enter the following to build the sample app:

$ bazel build //ios-app:ios-app

Bazel now launches and builds the sample app. During the build process, its output will appear similar to the following:

INFO: Found 1 target...
Target //ios-app:ios-app up-to-date:
  bazel-bin/ios-app/ios-app.ipa
  bazel-bin/ios-app/ios-app.xcodeproj/project.pbxproj
INFO: Elapsed time: 3.765s, Critical Path: 3.44s

Find the build outputs

The .ipa file and other outputs are located in the $WORKSPACE/bazel-bin/ios-app directory.

Run/Debug the app on the simulator

You can now run the app from Xcode using the iOS Simulator. To run the app, open the project directory $WORKSPACE/bazel-bin/ios-app/ios-app.xcodeproj in Xcode, choose an iOS Simulator as the runtime scheme and then click the Run button.

Note: If you change anything about the project file set in Xcode (for example, if you add or remove a file, or add or change a dependency), you must rebuild the app using Bazel and then re-open the project.

Build the app for a device

You need to set up bazel so that it can find the appropriate provisioning profile for the device you want to build for. To set up the “default” provisioning profile for all bazel builds:

Go to Apple Profiles and download the appropriate provisioning profile for your device. If this is confusing, please refer to Apple's documentation.
Move your profile into $WORKSPACE/tools/objc.
Optional - You may want to add your profile to your .gitignore.

Edit $WORKSPACE/tools/objc/BUILD and add:

filegroup(
    name = "default_provisioning_profile",
    srcs = ["<NAME OF YOUR PROFILE>.mobileprovision"],
)

Now you should be able to build the app for your device:

$ bazel build //ios-app:ios-app --ios_multi_cpus=armv7,arm64

This will build the app “fat”. If you would prefer just to build for your specific device architecture you can designate a single architecture.

If you would like to select a specific Xcode version/SDK version you can do so with the --xcode_version=7.2 --ios_sdk_version=9.2 options. Make sure that the Xcode version that you select has the appropriate SDK installed in it.

If you would like to specify a minimum version of iOS to run against, you can do so with the --ios_minimum_os=7.0 option.

Install the app on a device

The easiest way to install the app on the device is to launch Xcode and use the Windows > Devices command. Select your plugged in device from the list on the left, and then add the app by clicking on the “plus” sign under installed apps and selecting the .ipa that you built.

If your app does not launch, please make sure that your device was on your provisioning profile. The View Device Logs button on the Devices screen in Xcode may provide other information as to what has gone wrong.

What's next

The next step is to build a backend server for the two mobile apps you built in this tutorial.