Cocoapods with multiple projects: Firebase causes "Class XXX is implemented in both (...)" warning

I'm currently working on a Swift project where the workspace contains multiple projects (ACM...) due to company decision.

When adding Firebase with Cocoapods, I need it in two of the projects (in 'myapp' and 'ACMLoyalty'). So my .podfile looks like this:

workspace 'myapp.xcworkspace'
platform :ios, '12.0'
use_frameworks!

def shared_pods
  source 'https://github.com/CocoaPods/Specs.git'

  pod 'Nuke', '9.2.3'
  pod 'Alamofire', '~> 4.9.1'
  pod 'DeepDiff', '2.3.1'
end

def firebase_pods
  pod 'Firebase/Analytics', '7.4.0'
  pod 'Firebase/Crashlytics', '7.4.0'
  pod 'Firebase', '7.4.0'
end

def appcenter_pods
  pod 'AppCenter', '4.1.0'
  pod 'AppCenter/Distribute', '4.1.0'
end

project 'myapp.xcodeproj'
project 'ACMCore/ACMCore.xcodeproj'
project 'ACMData/ACMData.xcodeproj'
project 'ACMLoyalty/ACMLoyalty.xcodeproj'
project 'ACMMVVM/ACMMVVM.xcodeproj'
project 'ACMNetwork/ACMNetwork.xcodeproj'
project 'ACMShared/ACMShared.xcodeproj'

target :myapp do
  project 'myapp.xcodeproj'
  shared_pods
  firebase_pods
  appcenter_pods
end

target :ACMCore do
  project 'ACMCore/ACMCore.xcodeproj'
  shared_pods
end

target :ACMData do
  project 'ACMData/ACMData.xcodeproj'
  shared_pods
end

target :ACMLoyalty do
  use_frameworks! :linkage => :dynamic
  project 'ACMLoyalty/ACMLoyalty.xcodeproj'
  shared_pods
  firebase_pods

  target 'ACMLoyaltyTests' do
    inherit! :search_paths
    shared_pods
    firebase_pods
  end

  target 'ACMLoyaltyTestHost' do
    inherit! :search_paths
    shared_pods
    firebase_pods
  end
end

target :ACMMVVM do
  project 'ACMMVVM/ACMMVVM.xcodeproj'
  shared_pods

  target 'ACMMVVMTests' do
    inherit! :search_paths
    shared_pods
  end
end

target :ACMNetwork do
  project 'ACMNetwork/ACMNetwork.xcodeproj'
  shared_pods

  target 'ACMNetworkTests' do
    inherit! :search_paths
    shared_pods
  end
end

target :ACMShared do
  project 'ACMShared/ACMShared.xcodeproj'
  shared_pods

  target 'ACMSharedTests' do
    inherit! :search_paths
    shared_pods
  end
end

post_install do |installer|
  installer.pods_project.targets.each do |target|
    target.build_configurations.each do |config|
      if Gem::Version.new('9.0') > Gem::Version.new(config.build_settings['IPHONEOS_DEPLOYMENT_TARGET'])
        config.build_settings['IPHONEOS_DEPLOYMENT_TARGET'] = '9.0'
      end
    end
  end
end

Problem:

During run-time I get following warnings in the console:

objc[2946]: Class FIRAnalyticsConnector is implemented in both /private/var/containers/Bundle/Application/05B31227-083E-42A7-9E27-DB7924A754B9/myapp.app/Frameworks/ACMLoyalty.framework/ACMLoyalty (0x107c4d1b8) and /private/var/containers/Bundle/Application/05B31227-083E-42A7-9E27-DB7924A754B9/myapp.app/myapp (0x104217298). One of the two will be used. Which one is undefined.

This is just one line as sample, but there are a lot of other Firebase classes listed with the same description.

After some research I know, that the problem is, that Firebase is a static library and will be simply copied to the specific target which causes this issue. With the other libraries (dynamic) this problem doesn't occur.

Does anybody have a solution for my problem?

Edit: Answer @mbi

I already tried a solution with abstract_target.

Please find my .podfile for this attempt:

# Uncomment the next line to define a global platform for your project
workspace 'myapp.xcworkspace'
platform :ios, '12.0'
use_frameworks!

project 'myapp.xcodeproj'
project 'ACMCore/ACMCore.xcodeproj'
project 'ACMData/ACMData.xcodeproj'
project 'ACMLoyalty/ACMLoyalty.xcodeproj'
project 'ACMMVVM/ACMMVVM.xcodeproj'
project 'ACMNetwork/ACMNetwork.xcodeproj'
project 'ACMShared/ACMShared.xcodeproj'

abstract_target 'myapp-app' do
  source 'https://github.com/CocoaPods/Specs.git'

  pod 'Nuke', '9.2.3'
  pod 'Alamofire', '~> 4.9.1'
  pod 'DeepDiff', '2.3.1'

  pod 'Firebase/Analytics', '7.4.0'
  pod 'Firebase/Crashlytics', '7.4.0'
  pod 'Firebase', '7.4.0'

  def appcenter_pods
    pod 'AppCenter', '4.1.0'
    pod 'AppCenter/Distribute', '4.1.0'
  end

  target :myapp do
    project 'myapp.xcodeproj'
    appcenter_pods
  end

  target :ACMCore do
    project 'ACMCore/ACMCore.xcodeproj'
  end

  target :ACMData do
    project 'ACMData/ACMData.xcodeproj'
  end

  target :ACMLoyalty do
    project 'ACMLoyalty/ACMLoyalty.xcodeproj'

    target 'ACMLoyaltyTests' do
    end

    target 'ACMLoyaltyTestHost' do
    end
  end

  target :ACMMVVM do
    project 'ACMMVVM/ACMMVVM.xcodeproj'

    target 'ACMMVVMTests' do
    end
  end

  target :ACMNetwork do
    project 'ACMNetwork/ACMNetwork.xcodeproj'

    target 'ACMNetworkTests' do
    end
  end

  target :ACMShared do
    project 'ACMShared/ACMShared.xcodeproj'

    target 'ACMSharedTests' do
    end
  end
end

post_install do |installer|
  installer.pods_project.targets.each do |target|
    target.build_configurations.each do |config|
      if Gem::Version.new('9.0') > Gem::Version.new(config.build_settings['IPHONEOS_DEPLOYMENT_TARGET'])
        config.build_settings['IPHONEOS_DEPLOYMENT_TARGET'] = '9.0'
      end
    end
  end
end

The problem is, with this solution I have even more warning, because Firebase is built in ALL projects and conflicts.

EDIT2: With the answer of @arturdev I got it working without the `... implemented in both...` warning with following podfile:

# Uncomment the next line to define a global platform for your project
workspace 'myapp.xcworkspace'
platform :ios, '12.0'
use_frameworks!

project 'myapp.xcodeproj'
project 'ACMCore/ACMCore.xcodeproj'
project 'ACMData/ACMData.xcodeproj'
project 'ACMLoyalty/ACMLoyalty.xcodeproj'
project 'ACMMVVM/ACMMVVM.xcodeproj'
project 'ACMNetwork/ACMNetwork.xcodeproj'
project 'ACMShared/ACMShared.xcodeproj'

abstract_target 'myapp-app' do
  source 'https://github.com/CocoaPods/Specs.git'

  pod 'Nuke', '9.2.3'
  pod 'Alamofire', '~> 4.9.1'
  pod 'DeepDiff', '2.3.1'

  def firebase_pods
    pod 'Firebase/Analytics', '7.4.0'
    pod 'Firebase/Crashlytics', '7.4.0'
    pod 'Firebase', '7.4.0'
  end

  def appcenter_pods
    pod 'AppCenter', '4.1.0'
    pod 'AppCenter/Distribute', '4.1.0'
  end

  target :myapp do
    project 'myapp.xcodeproj'
    firebase_pods
    appcenter_pods

    target 'myappTests' do
    end
  end

  target :ACMCore do
    project 'ACMCore/ACMCore.xcodeproj'

    target 'ACMCoreTests' do
      firebase_pods
    end
  end

  target :ACMData do
    project 'ACMData/ACMData.xcodeproj'

    target 'ACMDataTests' do
      firebase_pods
    end
  end

  target :ACMLoyalty do
    project 'ACMLoyalty/ACMLoyalty.xcodeproj'
    firebase_pods

    target 'ACMLoyaltyTests' do
    end

    target 'ACMLoyaltyTestHost' do
    end
  end

  target :ACMMVVM do
    project 'ACMMVVM/ACMMVVM.xcodeproj'

    target 'ACMMVVMTests' do
    end
  end

  target :ACMNetwork do
    project 'ACMNetwork/ACMNetwork.xcodeproj'

    target 'ACMNetworkTests' do
    end
  end

  target :ACMShared do
    project 'ACMShared/ACMShared.xcodeproj'

    target 'ACMSharedTests' do
    end
  end
end

PROJECT_ROOT_DIR = File.dirname(File.expand_path(__FILE__))
PODS_DIR = File.join(PROJECT_ROOT_DIR, 'Pods')
PODS_TARGET_SUPPORT_FILES_DIR = File.join(PODS_DIR, 'Target Support Files')

post_install do |installer|

  ## For more information: https://stackoverflow.com/questions/65904011/cocoapods-with-multiple-projects-firebase-causes-class-xxx-is-implemented-in-b
  remove_static_framework_duplicate_linkage({
     'ACMLoyalty' => ['FBLPromises', 'FIRAnalyticsConnector', 'FirebaseAnalytics', 'FirebaseCore', 'FirebaseCoreDiagnostics', 'FirebaseCrashlytics', 'FirebaseInstallations', 'GoogleAppMeasurement', 'GoogleDataTransport', 'GoogleUtilities']
  })

  installer.pods_project.targets.each do |target|
    target.build_configurations.each do |config|
      #config.build_settings['LD_NO_PIE'] = 'NO'
      if Gem::Version.new('9.0') > Gem::Version.new(config.build_settings['IPHONEOS_DEPLOYMENT_TARGET'])
        config.build_settings['IPHONEOS_DEPLOYMENT_TARGET'] = '9.0'
      end
    end
  end
end

# CocoaPods provides the abstract_target mechanism for sharing dependencies between distinct targets.
# However, due to the complexity of our project and use of shared frameworks, we cannot simply bundle everything under
# a single abstract_target. Using a pod in a shared framework target and an app target will cause CocoaPods to generate
# a build configuration that links the pod's frameworks with both targets. This is not an issue with dynamic frameworks,
# as the linker is smart enough to avoid duplicate linkage at runtime. Yet for static frameworks the linkage happens at
# build time, thus when the shared framework target and app target are combined to form an executable, the static
# framework will reside within multiple distinct address spaces. The end result is duplicated symbols, and global
# variables that are confined to each target's address space, i.e not truly global within the app's address space.
#
# Previously we avoided this by linking the static framework with a single target using an abstract_target, and then
# provided a shim to expose their interfaces to other targets. The new approach implemented here removes the need for
# shim by modifying the build configuration generated by CocoaPods to restrict linkage to a single target.
def remove_static_framework_duplicate_linkage(static_framework_pods)
  puts "Removing duplicate linkage of static frameworks"

  Dir.glob(File.join(PODS_TARGET_SUPPORT_FILES_DIR, "Pods-*")).each do |path|
    pod_target = path.split('-', -1).last

    static_framework_pods.each do |target, pods|
      next if pod_target == target
      frameworks = pods.map { |pod| identify_frameworks(pod) }.flatten

      Dir.glob(File.join(path, "*.xcconfig")).each do |xcconfig|
        lines = File.readlines(xcconfig)

        if other_ldflags_index = lines.find_index { |l| l.start_with?('OTHER_LDFLAGS') }
          other_ldflags = lines[other_ldflags_index]

          frameworks.each do |framework|
            other_ldflags.gsub!("-framework \"#{framework}\"", '')
          end

          File.open(xcconfig, 'w') do |fd|
            fd.write(lines.join)
          end
        end
      end
    end
  end
end

def identify_frameworks(pod)
  frameworks = Dir.glob(File.join(PODS_DIR, pod, "**/*.framework")).map { |path| File.basename(path) }

  if frameworks.any?
    return frameworks.map { |f| f.split('.framework').first }
  end

  return pod
end

Solution

Some of the pod dependencies are being compiled as a static library and not dynamic (f.e. Firebase and other Google libs).

A static framework can't be linked more than once (f.e. in a framework target and in a main target which also links the framework above), because the linkage of static frameworks happens during build-time, yet for the dynamic frameworks the linkage happens on runtime and the linker is smart enough to avoid duplications.

Therefore you need to write a script in your podfile to remove static library linkages.

A dirty example:

post_install do |installer|
  remove_static_framework_duplicate_linkage({
        'FrameworkTarget1' => ['Firebase', 'FirebaseAnalytics', 'FirebaseCore', 'FirebaseCoreDiagnostics', 'FirebaseCoreDiagnosticsInterop', 'FirebaseInstanceID', 'FirebaseInstallations', 'GoogleAppMeasurement', 'GoogleDataTransport', 'GoogleDataTransportCCTSupport', 'GoogleUtilities'],
        'FrameworkTarget2' => ['GoogleMaps', 'GooglePlaces'],
  })

    installer.pods_project.targets.each do |target|
        target.build_configurations.each do |config|
                config.build_settings['LD_NO_PIE'] = 'NO'
                config.build_settings.delete 'IPHONEOS_DEPLOYMENT_TARGET'
        end
  end
end


# CocoaPods provides the abstract_target mechanism for sharing dependencies between distinct targets.
# However, due to the complexity of our project and use of shared frameworks, we cannot simply bundle everything under
# a single abstract_target. Using a pod in a shared framework target and an app target will cause CocoaPods to generate
# a build configuration that links the pod's frameworks with both targets. This is not an issue with dynamic frameworks,
# as the linker is smart enough to avoid duplicate linkage at runtime. Yet for static frameworks the linkage happens at
# build time, thus when the shared framework target and app target are combined to form an executable, the static
# framework will reside within multiple distinct address spaces. The end result is duplicated symbols, and global
# variables that are confined to each target's address space, i.e not truly global within the app's address space.
#
# Previously we avoided this by linking the static framework with a single target using an abstract_target, and then
# provided a shim to expose their interfaces to other targets. The new approach implemented here removes the need for
# shim by modifying the build configuration generated by CocoaPods to restrict linkage to a single target.
def remove_static_framework_duplicate_linkage(static_framework_pods)
  puts "Removing duplicate linkage of static frameworks"

  Dir.glob(File.join(PODS_TARGET_SUPPORT_FILES_DIR, "Pods-*")).each do |path|
    pod_target = path.split('-', -1).last

    static_framework_pods.each do |target, pods|
      next if pod_target == target
      frameworks = pods.map { |pod| identify_frameworks(pod) }.flatten

      Dir.glob(File.join(path, "*.xcconfig")).each do |xcconfig|
        lines = File.readlines(xcconfig)

        if other_ldflags_index = lines.find_index { |l| l.start_with?('OTHER_LDFLAGS') }
          other_ldflags = lines[other_ldflags_index]

          frameworks.each do |framework|
            other_ldflags.gsub!("-framework \"#{framework}\"", '')
          end

          File.open(xcconfig, 'w') do |fd|
            fd.write(lines.join)
          end
        end
      end
    end
  end
end

def identify_frameworks(pod)
  frameworks = Dir.glob(File.join(PODS_DIR, pod, "**/*.framework")).map { |path| File.basename(path) }

  if frameworks.any?
    return frameworks.map { |f| f.split('.framework').first }
  end

  return pod
end

Cocoapods with multiple projects: Firebase causes "Class XXX is implemented in both (...)" warning

Problem:

Edit: Answer @mbi

EDIT2: With the answer of @arturdev I got it working without the ... implemented in both... warning with following podfile:

EDIT2: With the answer of @arturdev I got it working without the `... implemented in both...` warning with following podfile: