Set deployment target for CocoaPods's pod

I use CocoaPods to manage dependencies in my project. I've written Podfile:

target 'MyApp' do
  platform :ios, '8.0'
  # Uncomment this line if you're using Swift or would like to use dynamic frameworks
  #use_frameworks!

  # Pods for MyApp
  pod 'KeepLayout', :git => 'https://github.com/iMartinKiss/KeepLayout', :tag => 'v1.6.0'
  pod 'EasyMapping'

  target 'MyAppTests' do
    inherit! :search_paths
    # Pods for testing
  end

  target 'MyAppUITests' do
    inherit! :search_paths
    # Pods for testing
  end

end

This file works well with CocoaPods 0.x but I can't compile project after I've updated to CocoaPods 1.0. After I've run

pod update 

I can't compile my project with error:

> /Users/<...>/Pods/KeepLayout/Sources/KeepAttribute.m:195:1: Cannot synthesize weak property because the current deployment target does not support weak references

I've seen that every library is builded with different deployment target. For example KeepLayout is builded with 4.3 deployment target.

How I can determine build target for every pod dependency?

While some development versions of CocoaPods (as well as pre-1.0 versions) may have propagated the deployment target of the project down to the pods, this is no longer the case in 1.0. To work around this, the current developer recommends using a post-install hook.

Here's a brute force approach to force a hard-coded deployment target for every pod in the generated Pods project. Paste this at the end of your Podfile:

post_install do |installer|
  installer.pods_project.targets.each do |target|
    target.build_configurations.each do |config|
      config.build_settings['IPHONEOS_DEPLOYMENT_TARGET'] = '9.2'
    end
  end
end

Since the Podfile uses a directive like platform :ios, '9.0' to specify "iOS Deployment Target" (aka IPHONEOS_DEPLOYMENT_TARGET) for the Pods/Pods.xcodeproj project, you just need to remove the Deployment Target info from each build target.
Do it by adding this to your Podfile

platform :ios, '9.0' # set IPHONEOS_DEPLOYMENT_TARGET for the pods project
post_install do |installer|
  installer.pods_project.targets.each do |target|
    target.build_configurations.each do |config|
      config.build_settings.delete 'IPHONEOS_DEPLOYMENT_TARGET'
    end
  end
end

Inspired by the github post and Alex Nauda's answer.

While the accepted answer by Alex Nauda is good, but letting the Pods inherit the target from the app might be a much better solution. 

app_ios_deployment_target = Gem::Version.new('9.2') # Change to your current deployment target

platform :ios, app_ios_deployment_target.version

# Let Pods targets inherit deployment target from the app
# This solution is suggested here: https://github.com/CocoaPods/CocoaPods/issues/4859
post_install do |installer|
  installer.pods_project.targets.each do |target|
    target.build_configurations.each do |configuration|
      pod_ios_deployment_target = Gem::Version.new(configuration.build_settings['IPHONEOS_DEPLOYMENT_TARGET'])
      if pod_ios_deployment_target <= app_ios_deployment_target
        configuration.build_settings.delete 'IPHONEOS_DEPLOYMENT_TARGET'
      end
    end
  end
end

change target to "11.0"

platform :ios, '11.0'

Here is the way to set deployment target permanently for pod targets.

Goto -> podfile -> Add below code

post_install do |installer|
  installer.pods_project.targets.each do |target|
    target.build_configurations.each do |config|
      config.build_settings['IPHONEOS_DEPLOYMENT_TARGET'] = "12.0"
     end
  end
end

1. Search for IPHONEOS_DEPLOYMENT_TARGET

2. Change the iOS Deployment Target