老款MacBook系统Monterey(MacOS 12)由于brew停止了从上游下载cocoapods提示不支持os12系统，无法安装最新版cocoapods，本文讲述了另一种方法来更新cocoapods
原文链接：http://www.kovli.com/2024/12/18/old-macos-install-cocoapods/
作者:Kovli
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尝试过的方法：
sudo gem install cocoapods
sudo gem install cocoapods -pre
gem install cocoapods --user-install
sudo gem update cocoapods --version 1.16.2
均无法成功安装，系统ruby是2.6
后来尝试用brew安装
brew install ruby
提示报错如下：
Error: Your Command Line Tools are too outdated.
Update them from Software Update in System Preferences.
If that doesn't show you any updates, run:
sudo rm -rf /Library/Developer/CommandLineTools
sudo xcode-select --install
Alternatively, manually download them from:
https://developer.apple.com/download/all/.
You should download the Command Line Tools for Xcode 14.2.
经过检查是安装了命令行工具14.2的，也重复安装一遍还是报错同样错误，判断是版本太低不支持，但是xCode14.2已经是OS12系统的最新版本了，受限于系统无法升级。
于是想着升级下当前系统所支持的最高ruby版本2.7.2
brew install ruby@2.7
报错如下，
Error: ruby@2.7 has been disabled because it is not supported upstream! It was disabled on 2024-06-15.
尝试brew安装ruby2.6
brew install ruby@2.6
报错如下
No available formula with the name "ruby@2.6". Did you mean ruby@2.7, ruby@3.2, ruby@3.1 or ruby@3.0?
也就是说brew只支持安装ruby3以上
于是安装3.0版本试试
brew install ruby@3.0
结果报错如下
Error: You are using macOS 12.
We (and Apple) do not provide support for this old version.
说明brew已经不支持macOS12系统安装ruby3了，到这里可以看出，brew在macOS12系统已经安装不了ruby了
于是考虑用rvm
curl -L get.rvm.io | bash -s stable
顺利安装了rvm最新版
rvm 1.29.12 (latest) by Michal Papis, Piotr Kuczynski, Wayne E. Seguin [https://rvm.io]
先尝试安装ruby 3以上的，结果没成功，经过查询，最高支持安装2.7.2
rvm install 2.7.2
提示报错
Error running '__rvm_make -j8',
经检查问题出在openssl
卸载openssl
brew uninstall --ignore-dependencies openssl@3
重装低版本
rm -rf /usr/local/etc/openssl@1.1
brew reinstall openssl@1.1
提示报错
Error: openssl@1.1 has been disabled because it is not supported upstream! It was disabled on 2024-10-24.
此时有种换电脑的冲动了，但是不想让老外的计谋得逞，继续努力兼容!
brew edit openssl@1.1
会提示编辑如下文件
Editing /usr/local/opt/openssl@1.1/.brew/openssl@1.1.rb
通过编辑器或者vim编辑，注释下面这行
deprecate! date: "2023-11-11", because: :unsupported
# deprecate! date: "2023-11-11", because: :unsupported
然后执行：
HOMEBREW_NO_INSTALL_FROM_API=1 brew install openssl@1.1
HOMEBREW_NO_INSTALL_FROM_API=1 这个环境变量的作用就是告诉brew 不使用api中的formula而是使用你自己编辑后的， 这样就可以正常安装被brew禁止disable的软件包了。
上面的执行完再次安装2.7.2就可以成功
rvm install 2.7.2
设为默认ruby
rvm use 2.7.2 --default
更新了ruby从系统默认的2.6到rvm安装的2.7.2后再次尝试安装cocoapods
sudo gem install cocoapods -v 1.16.2 -n /usr/local/bin
提示报错
ERROR: Error installing cocoapods:
The last version of securerandom (>= 0.3) to support your Ruby & RubyGems was 0.3.2. Try installing it with `gem install securerandom -v 0.3.2` and then running the current command again
securerandom requires Ruby version >= 3.1.0. The current ruby version is 2.7.2.137.
按照指引继续安装securerandom
sudo gem install -n /usr/local/bin securerandom -v 0.3.2
然后重试
sudo gem install cocoapods -v 1.16.2 -n /usr/local/bin
提示报错
ERROR: Error installing cocoapods:
The last version of activesupport (>= 5.0, < 8) to support your Ruby & RubyGems was 7.1.5.1. Try installing it with `gem install activesupport -v 7.1.5.1` and then running the current command again
activesupport requires Ruby version >= 3.1.0. The current ruby version is 2.7.2.137.
按照指引开始安装activesupport
sudo gem install -n /usr/local/bin activesupport -v 7.1.5.1
继续重试
sudo gem install -n /usr/local/bin cocoapods -v 1.16.2
这次终于没报错了，安装成功，检查版本
~ pod --version
1.16.2
成功更新到新版cocoapods
tips:
1、RVM官方网站
https://rvm.io/workflow/examples#rvm-list
2、ruby可安装的版本信息
rvm list known
3、cocoapods所有版本
https://rubygems.org/gems/cocoapods/versions
4、cocoapods官网
https://guides.cocoapods.org/using/getting-started.html
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http://www.kovli.com/2024/12/18/old-macos-install-cocoapods/
