# 用于存储target相关的信息，整合pods下target的信息
  autoload :AggregateTarget,           'cocoapods/target/aggregate_target'

  # 实现了pod下的各种命令，具体的命令可以通过pod --help来查看
  autoload :Command,                   'cocoapods/command'

  # 用于移除cocoapods
  autoload :Deintegrator,              'cocoapods_deintegrate'

  # 用于支持可执行文件执行的模块
  autoload :Executable,                'cocoapods/executable'

  # 用于初始化外部资源类
  autoload :ExternalSources,           'cocoapods/external_sources'

  # 负责根据podfile生成Pods库
  autoload :Installer,                 'cocoapods/installer'

  # 提供了cocoapods的hook机制，便于plugins的编写
  autoload :HooksManager,              'cocoapods/hooks_manager'

  # 保存target的信息，用来编译单个pod
  autoload :PodTarget,                 'cocoapods/target/pod_target'

  # pod工程
  autoload :Project,                   'cocoapods/project'

  # 根据Podfile生成target的specifications
  autoload :Resolver,                  'cocoapods/resolver'

  # 用于支持Cocoapods install的时候用的目录操作
  autoload :Sandbox,                   'cocoapods/sandbox'

  # 管理所有的源代码
  autoload :SourcesManager,            'cocoapods/sources_manager'

  # 描述pods target
  autoload :Target,                    'cocoapods/target'

  # 检查一个specification是否合法
  autoload :Validator,                 'cocoapods/validator'

def install!
  prepare  # 做一些准备工作
  resolve_dependencies   # 解析依赖关系
  download_dependencies    # 下载依赖库
  determine_dependency_product_types   # 查看依赖是静态库还是动态库
  verify_no_duplicate_framework_names    # 检查是否有重复framework
  verify_no_static_framework_transitive_dependencies   # 检查是否静态库有传递依赖
  verify_framework_usage # 检查framework的使用，主要跟swift相关
  generate_pods_project # 生成pods项目文件
  integrate_user_project if installation_options.integrate_targets?  # 集成用户项目文件
  perform_post_install_actions # 执行install后处理
end

def resolve_dependencies
  analyzer = create_analyzer # 创建分析器

  plugin_sources = run_source_provider_hooks
  analyzer.sources.insert(0, *plugin_sources)

  UI.section 'Updating local specs repositories' do
    analyzer.update_repositories # 这里是依赖解析的核心功能，用于下载和更新相关的依赖库
  end unless config.skip_repo_update?

  UI.section 'Analyzing dependencies' do
    analyze(analyzer)
    validate_build_configurations
    clean_sandbox
  end
end

def generate_pods_project
  UI.section 'Generating Pods project' do
    prepare_pods_project        # 做一些准备工作,比如新建project、设置platform以及deployment_target等
    install_file_references  # 整合源文件和资源到Pods项目中
    install_libraries # 构建pod_targets和aggregate_targets
    set_target_dependencies # 增加每个aggregate目标的目标依赖，并将这个目标link在一起
    run_podfile_post_install_hooks # 执行hooks
    write_pod_project # 生成pod project文件
    share_development_pod_schemes
    write_lockfiles # 更新Podfile和PodLockfile
  end
end

 # FileReferencesInstaller
def install!
  refresh_file_accessors     # 从文件系统中读取文件
  add_source_files_references # 将源文件加到Pods项目中
  add_frameworks_bundles # 将framework加到Pods项目中
  add_vendored_libraries # 将库加到Pods项目中
  add_resources # 将资源加到Pods项目中
  link_headers # 创建头文件的链接
end

module Project
  module Options
    def options
      [
        ['--no-repo-update', 'Skip running `pod repo update` before install'],
      ].concat(super)
    end
  end

  def self.included(base)
    base.extend Options
  end

  def initialize(argv)
    config.skip_repo_update = !argv.flag?('repo-update', !config.skip_repo_update)
    super
  end

  # Runs the installer.
  #
  # @param  [Hash, Boolean, nil] update
  #         Pods that have been requested to be updated or true if all Pods
  #         should be updated
  #
  # @return [void]
  #
  def run_install_with_update(update)
    installer = Installer.new(config.sandbox, config.podfile, config.lockfile)
    installer.update = update
    installer.install!
  end
end


class Install < Command
  include Project

  self.summary = 'Install project dependencies to Podfile.lock versions'

  self.description = <<-DESC
    Downloads all dependencies defined in `Podfile` and creates an Xcode
    Pods library project in `./Pods`.

    The Xcode project file should be specified in your `Podfile` like this:

        xcodeproj 'path/to/XcodeProject'

    If no xcodeproj is specified, then a search for an Xcode project will
    be made. If more than one Xcode project is found, the command will
    raise an error.

    This will configure the project to reference the Pods static library,
    add a build configuration file, and add a post build script to copy
    Pod resources.
  DESC

  def run
    verify_podfile_exists!
    run_install_with_update(false)
  end
end

def run_install_with_update(update)
  installer = Installer.new(config.sandbox, config.podfile, config.lockfile)
  installer.update = update
  installer.install!
end