CocoaPodsのインストールで色々ハマった。

iOS開発にてKiwiを使って、テストコードを書くために  
まずはCocoaPodsをインストールしようとしたのだが、色々ハマったのでメモ。

```bash
$ gem install Cocoapods

"/Users/user_name/.rvm/rubies/ruby-1.9.3-p362/bin/ruby" -rubygems /Users/user_name/.rvm/gems/ruby-1.9.3-p362/gems/rake-10.3.1/bin/rake RUBYARCHDIR=/Users/user_name/.rvm/gems/ruby-1.9.3-p362/gems/xcodeproj-0.16.1/ext RUBYLIBDIR=/Users/user_name/.rvm/gems/ruby-1.9.3-p362/gems/xcodeproj-0.16.1/ext
/Users/user_name/.rvm/rubies/ruby-1.9.3-p362/bin/ruby extconf.rb
checking for -std=c99 option to compiler... *** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers.  Check the mkmf.log file for more
details.  You may need configuration options.

Provided configuration options:
        --with-opt-dir
        --with-opt-include
        --without-opt-include=${opt-dir}/include
        --with-opt-lib
        --without-opt-lib=${opt-dir}/lib
        --with-make-prog
        --without-make-prog
        --srcdir=.
        --curdir
        --ruby=/Users/user_name/.rvm/rubies/ruby-1.9.3-p362/bin/ruby
/Users/user_name/.rvm/rubies/ruby-1.9.3-p362/lib/ruby/1.9.1/mkmf.rb:381:in `try_do': The compiler failed to generate an executable file. (RuntimeError)
You have to install development tools first.
        from /Users/user_name/.rvm/rubies/ruby-1.9.3-p362/lib/ruby/1.9.1/mkmf.rb:491:in `block in try_compile'
        from /Users/user_name/.rvm/rubies/ruby-1.9.3-p362/lib/ruby/1.9.1/mkmf.rb:443:in `with_werror'
        from /Users/user_name/.rvm/rubies/ruby-1.9.3-p362/lib/ruby/1.9.1/mkmf.rb:491:in `try_compile'
        from extconf.rb:24:in `block in <main>'
        from /Users/user_name/.rvm/rubies/ruby-1.9.3-p362/lib/ruby/1.9.1/mkmf.rb:790:in `block in checking_for'
        from /Users/user_name/.rvm/rubies/ruby-1.9.3-p362/lib/ruby/1.9.1/mkmf.rb:284:in `block (2 levels) in postpone'
        from /Users/user_name/.rvm/rubies/ruby-1.9.3-p362/lib/ruby/1.9.1/mkmf.rb:254:in `open'
        from /Users/user_name/.rvm/rubies/ruby-1.9.3-p362/lib/ruby/1.9.1/mkmf.rb:284:in `block in postpone'
        from /Users/user_name/.rvm/rubies/ruby-1.9.3-p362/lib/ruby/1.9.1/mkmf.rb:254:in `open'
        from /Users/user_name/.rvm/rubies/ruby-1.9.3-p362/lib/ruby/1.9.1/mkmf.rb:280:in `postpone'
        from /Users/user_name/.rvm/rubies/ruby-1.9.3-p362/lib/ruby/1.9.1/mkmf.rb:789:in `checking_for'
        from extconf.rb:23:in `<main>'
rake aborted!
Command failed with status (1): [/Users/user_name/.rvm/rubies/ruby-1.9.3-p3...]
/Users/user_name/.rvm/gems/ruby-1.9.3-p362/gems/xcodeproj-0.16.1/ext/xcodeproj/Rakefile:37:in `block in <top (required)>'
Tasks: TOP => default => ext
(See full trace by running task with --trace)
```

You have to install development tools first.  
と言われるので、開発ツールが必要らしい。

[ここ](http://stackoverflow.com/questions/20939568/error-error-installing-cocoapods-error-failed-to-build-gem-native-extension)を参考にコマンドを試してみる。

```bash
$ xcode-select --install
```

そこから下記にコマンドをもう一度、試してみる。

```bash
$ gem install cocoapods
```

ダメだ、さっきと同じエラーが起こった。   

[ここ](http://stackoverflow.com/questions/20939568/error-error-installing-cocoapods-error-failed-to-build-gem-native-extension)を参考に今度は下のコマンドを試してみる。

```bash
$ brew install apple-gcc42
==> Downloading https://downloads.sf.net/project/machomebrew/Bottles/apple-gcc42-4.2.1-5666.3.mavericks.bottle.2.tar.gz
######################################################################## 100.0%
==> Pouring apple-gcc42-4.2.1-5666.3.mavericks.bottle.2.tar.gz
==> Caveats
NOTE:
This formula provides components that were removed from XCode in the 4.2
release. There is no reason to install this formula if you are using a
version of XCode prior to 4.2.

This formula contains compilers built from Apple's GCC sources, build
5666.3, available from:

  http://opensource.apple.com/tarballs/gcc

All compilers have a `-4.2` suffix. A GFortran compiler is also included.
==> Summary
?  /usr/local/Cellar/apple-gcc42/4.2.1-5666.3: 104 files, 75M
```

もう一回チャレンジ。

```bash
$ gem install cocoapods

Building native extensions.  This could take a while...
Fetching: cocoapods-try-0.2.0.gem (100%)
Fetching: escape-0.0.4.gem (100%)
Fetching: open4-1.3.3.gem (100%)
Fetching: cocoapods-0.32.1.gem (100%)

CHANGELOG:

## 0.32.1

##### Bug Fixes

* Fixed the Podfile `default_subspec` attribute in nested subspecs.
  [Fabio Pelosin][irrationalfab]
  [#2050](https://github.com/CocoaPods/CocoaPods/issues/2050)


Successfully installed xcodeproj-0.16.1
Successfully installed cocoapods-try-0.2.0
Successfully installed escape-0.0.4
Successfully installed open4-1.3.3
Successfully installed cocoapods-0.32.1
5 gems installed
Installing ri documentation for xcodeproj-0.16.1...
Installing ri documentation for cocoapods-try-0.2.0...
Installing ri documentation for escape-0.0.4...
Installing ri documentation for open4-1.3.3...
Installing ri documentation for cocoapods-0.32.1...
Installing RDoc documentation for xcodeproj-0.16.1...
Installing RDoc documentation for cocoapods-try-0.2.0...
Installing RDoc documentation for escape-0.0.4...
Installing RDoc documentation for open4-1.3.3...
Installing RDoc documentation for cocoapods-0.32.1...
```

お、うまくいった。
ちゃんと、インストールされているのを確認した。

```bash
$ gem list | grep cocoapods
cocoapods (0.32.1)
cocoapods-core (0.32.1)
cocoapods-downloader (0.5.0)
cocoapods-try (0.2.0)
```