class Xcodeproj::Project::PBXGroup

def <<(child) 

def <<(child)
  children << child
end

def files 

def files
  list_by_class(childReferences, Xcodeproj::Project::PBXFileReference) do |file|
    file.group = self
  end
end

def groups 

def groups
  list_by_class(childReferences, Xcodeproj::Project::PBXGroup)
end

def initialize(*) 

def initialize(*)
  super
  self.sourceTree ||= '<group>'
  self.childReferences ||= []
end

def source_files 

def source_files
  files = self.files.reject { |file| file.buildFiles.empty? }
  list_by_class(childReferences, Xcodeproj::Project::PBXFileReference, files) do |file|
    file.group = self
  end
end