iOS開發必備：cocoapods
一、什么是cocoapods？
CocoaPods是一個用來幫助我們管理第三方依賴庫的工具。
它可以解決庫與庫之間的依賴關系，下載庫的源代碼，同時通過創建一個Xcode的workspace來將這些第三方庫和我們的工程連接起來，供我們開發使用。
使用CocoaPods的目的是讓我們能自動化的、集中的、直觀的管理第三方開源庫（比如JSONKit，AFNetWorking等）。
二、如何安裝？
方法一：當然是官方的文檔最權威啦，這就需要去官網看看了。
CocoaPods是Swift和Objective-C Cocoa項目的依賴管理器。 它有超過28萬個圖書館，并在超過170萬的應用程序中使用。 CocoaPods可以幫助您優化擴展項目。
CocoaPods是用Ruby構建的，可以使用OS X上提供的默認Ruby安裝。我們建議您使用默認的ruby。
使用默認的Ruby安裝可能需要在安裝gem時使用sudo。 更多安裝說明在指南中。
https://guides.cocoapods.org/using/getting-started.html#getting-started
這是官方的安裝指南。
如果你英語和我一樣不太好的話，還是用民間的傳統方法吧。
方法二：小白新手安裝步驟詳解?。。?/h2>
CocoaPods是以Ruby gem包的形式被安裝的。Mac OS系統是自帶Ruby環境的。
可以先在終端（Terminal）輸入：sudo gem install cocoapods，如果不出錯的話，那是萬幸了，但是基本上都是會出現error的，因為ruby的軟件源rubygems.org因為使用亞馬遜的云服務，被我天朝屏蔽了，所以需要更新一下ruby的源。
保守起見首先還是先查看下當前ruby版本：
打開終端（Terminal）輸入?
ruby -v
2.更新Ruby源，網上的一種解決方案是將遠替換成淘寶的，不過現在淘寶的 ruby 源已經不維護了，請替換成 Ruby China，
具體輸入：
gem sources --removehttps://rubygems.org/? ? ?/*去掉ruby源*/
gem sources -ahttps://gems.ruby-china.org/? ? ? ?/*添加新的源*/
gem sources -l? ? ? /*查看當前ruby源*/
3.安裝：
具體輸入：
sudo gem install cocoapods
4.如果你的gem太老，可能也會有問題，可以嘗試用如下命令升級gem:
具體輸入：
sudo gem update --system
之后的新建podfile網上都有流程啦，自己動手一下，搜索。
我要說一下我遇到的問題。
cocoapods安裝及使用遇到的問題合集：
1.
安裝cocoapods過程中，需要輸入電腦密碼，輸入密碼的時候，你會發現光標和平常不一樣，而且你輸入的時候數字會顯示不出來，不用理會，直接輸入完按enter/return回車鍵。
2.當輸入“sudo gem install cocoapods”或者“sudo gem install -n /usr/local/bin cocoapods”
出現以下錯誤：
ERROR:? While executing gem ... (Gem::DependencyError)
Unable to resolve dependencies: cocoapods requires cocoapods-core (= 1.2.0), cocoapods-downloader (< 2.0, >= 1.1.3), cocoapods-trunk (< 2.0, >= 1.1.2), molinillo (~> 0.5.5), xcodeproj (< 2.0, >= 1.4.1)
yangyangyangdeMacBook-Pro:~ yang$ sudo nvram boot-args="rootless=0"
nvram: Error setting variable - 'boot-args': (iokit/common) general error
解決方法：
輸入：
rvm list known
出現錯誤：-bash: rvm: command not found
則繼續輸入：
curl -L get.rvm.io | bash -s stable
出現以下：
即表示rvm安裝完成。
繼續輸入：
rvm list known
出現以下：
會顯示出所有的ruby的版本
yangyangyangdeMacBook-Pro:~ yang$ rvm list known
# MRI Rubies
[ruby-]1.8.6[-p420]
[ruby-]1.8.7[-head] # security released on head
[ruby-]1.9.1[-p431]
[ruby-]1.9.2[-p330]
[ruby-]1.9.3[-p551]
[ruby-]2.0.0[-p648]
[ruby-]2.1[.10]
[ruby-]2.2[.6]
[ruby-]2.3[.3]
[ruby-]2.4[.0]
ruby-head
.
.
.
# IronRuby
ironruby[-1.1.3]
ironruby-head
繼續輸入：sudo gem install cocoa pods
出現以下：
yangyangyangdeMacBook-Pro:~ yang$ sudo gem install cocoa pods
Password:
Fetching: i18n-0.7.0.gem (100%)
Successfully installed i18n-0.7.0
Fetching: thread_safe-0.3.5.gem (100%)
Successfully installed thread_safe-0.3.5
Fetching: tzinfo-1.2.2.gem (100%)
Successfully installed tzinfo-1.2.2
Fetching: minitest-5.9.1.gem (100%)
Successfully installed minitest-5.9.1
Fetching: concurrent-ruby-1.0.2.gem (100%)
Successfully installed concurrent-ruby-1.0.2
Fetching: activesupport-5.0.1.gem (100%)
ERROR:? Error installing cocoa:
activesupport requires Ruby version >= 2.2.2.
ERROR:? Error installing pods:
activesupport requires Ruby version >= 2.2.2.
繼續輸入：rvm install 2.2.2? /*選擇安裝最新的Ruby*/
出現以下：
Searching for binary rubies, this might take some time.
Found remote file https://rvm_io.global.ssl.fastly.net/binaries/osx/10.12/x86_64/ruby-2.2.2.tar.bz2
Checking requirements for osx.
About to install Homebrew, press `Enter` for default installation in `/usr/local`,
type new path if you wish custom Homebrew installation (the path needs to be writable for user)
:
==> This script will install:
/usr/local/bin/brew
/usr/local/share/doc/homebrew
/usr/local/share/man/man1/brew.1
/usr/local/share/zsh/site-functions/_brew
/usr/local/etc/bash_completion.d/brew
/usr/local/Homebrew
Press RETURN to continue or any other key to abort
==> Downloading and installing Homebrew...
remote: Counting objects: 5079, done.
remote: Compressing objects: 100% (3186/3186), done.
remote: Total 5079 (delta 2798), reused 3338 (delta 1722), pack-reused 0
Receiving objects: 100% (5079/5079), 2.66 MiB | 44.00 KiB/s, done.
Resolving deltas: 100% (2798/2798), done.
From https://github.com/Homebrew/brew
...
* [new tag]? ? ? ? 1.1.9? ? ? -> 1.1.9
HEAD is now at dfad3f3 Merge pull request #2034 from reitermarkus/spec-gpg
==> Tapping homebrew/core
Cloning into '/usr/local/Homebrew/Library/Taps/homebrew/homebrew-core'...
remote: Counting objects: 4137, done.
remote: Compressing objects: 100% (4013/4013), done.
remote: Total 4137 (delta 30), reused 433 (delta 9), pack-reused 0
Receiving objects: 100% (4137/4137), 3.31 MiB | 87.00 KiB/s, done.
Resolving deltas: 100% (30/30), done.
Tapped 4010 formulae (4,166 files, 10.4M)
==> Cleaning up /Library/Caches/Homebrew...
==> Migrating /Library/Caches/Homebrew to /Users/yang/Library/Caches/Homebrew...
==> Deleting /Library/Caches/Homebrew...
Already up-to-date.
==> Installation successful!
==> Homebrew has enabled anonymous aggregate user behaviour analytics.
Read the analytics documentation (and how to opt-out) here:
https://git.io/brew-analytics
==> Next steps:
- Run `brew help` to get started
- Further documentation:
https://git.io/brew-docs
Installing requirements for osx.
Updating system.........
Installing required packages: autoconf, automake, libtool, pkg-config, coreutils, libyaml, readline, libksba, openssl...........
Certificates in '/usr/local/etc/openssl/cert.pem' are already up to date.
Requirements installation successful.
ruby-2.2.2 - #configure
ruby-2.2.2 - #download
% Total? ? % Received % Xferd? Average Speed? Time? ? Time? ? Time? Current
Dload? Upload? Total? Spent? ? Left? Speed
100 6854k? 100 6854k? ? 0? ? 0? 14400? ? ? 0? 0:08:07? 0:08:07 --:--:-- 17131
No checksum for downloaded archive, recording checksum in user configuration.
ruby-2.2.2 - #validate archive
ruby-2.2.2 - #extract
ruby-2.2.2 - #validate binary
ruby-2.2.2 - #setup
ruby-2.2.2 - #gemset created /Users/yang/.rvm/gems/ruby-2.2.2@global
ruby-2.2.2 - #importing gemset /Users/yang/.rvm/gemsets/global.gems.............
ruby-2.2.2 - #generating global wrappers........
ruby-2.2.2 - #gemset created /Users/yang/.rvm/gems/ruby-2.2.2
ruby-2.2.2 - #importing gemsetfile /Users/yang/.rvm/gemsets/default.gems evaluated to empty gem list
ruby-2.2.2 - #generating default wrappers........
Updating certificates in '/etc/openssl/cert.pem'.
mkdir: /etc/openssl: Permission denied
mkdir -p "/etc/openssl" failed, retrying with sudo
yang password required for 'mkdir -p /etc/openssl':
and sudo mkdir worked
繼續輸入：
sudo gem install cocoapods
出現以下：
最終看到了：26 gems installed
就代表最終cocoapods安裝好啦
三、如何新建Podfile文件？
終端輸入：
vim Podfile
點擊“i”，進入文件編輯模式
輸入：
platform :ios, '10.0'? /*設置iOS 10的版本號*/
target 'Cloud Weather' do? /*目標文件*/
pod 'AFNetworking'? ? /*輸入你要用到的第三方庫，后面可以設置版本號，如果不設置就是默認最新版本*/
end
編輯完成后，然后按Esc，并且輸入“ ：”號進入vim命令模式，然后在冒號后邊輸入wq
注意：鍵盤輸入 ：后，才能輸入wq?；剀嚭蟀l現PodTest項目總目錄中多一個Podfile文件
繼續在終端中輸入：
pod install
如上圖所示，
打開文件夾，會出現以下三個文件
