Change swift version base on podspec

change_swift_version.rb

post_install do |installer|
  installer.pods_project.targets.each do |target|
    target.build_configurations.each do |config|
      if config.name == 'Debug'
        config.build_settings['SWIFT_OPTIMIZATION_LEVEL'] = '-Onone'
        else
        config.build_settings['SWIFT_OPTIMIZATION_LEVEL'] = '-Owholemodule'
      end
      
      change_directly = false
      if change_directly
        config.build_settings['SWIFT_VERSION'] = '4.0'
      else
        # Handle framework only. skip .bundle, etc...
        next unless config.build_settings['WRAPPER_EXTENSION'].nil?
        
        puts "Checking swift verion of #{target.name} in #{config.name} configuration."
        
        pod_spec_meta = `pod spec cat #{target.name}`
        
        if !$?.success?
          puts "#{pod_spec_meta}. Skip."
          next
        end
        
        pod_sepc_hash = eval(pod_spec_meta)
        swift_version = pod_sepc_hash[:swift_version] || pod_sepc_hash[:pushed_with_swift_version]
        next unless swift_version.nil?
        
        if swift_version.to_f < 4.2
          puts "Swift version in #{target.name}.podspec is #{swift_version}, change to 4.0."
          config.build_settings['SWIFT_VERSION'] = '4.0'
        end
      end
    end
  end
end