Mac (El Capitan) で nokogiri のインストール @Ruby 2.3.1 でハマった

Ruby Mac OSX

いつものように

$ ~/.rbenv/plugins/ruby-build

$ git fetch origin

$ git rebase origin/master

$ rbenv install 2.3.1

$ rbenv global 2.3.1

$ gem install bundler

$ rbenv rehash

ここまでは全く問題なし。

つづいて Rails ディレクトリへ、

$ ~/projext_hogehoge/

$ rm -rf vendor/bundle

$ bundle install

....
....
Installing nokogiri 1.6.7.2 with native extensions

Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

    current directory: /Users/nyangry/workspace/some_project/vendor/bundle/gems/nokogiri-1.6.7.2/ext/nokogiri
/Users/nyangry/.rbenv/versions/2.3.1/bin/ruby -r ./siteconf20160513-85661-v1vt0k.rb extconf.rb --use-system-libraries
checking if the C compiler accepts ... yes
checking if the C compiler accepts -Wno-error=unused-command-line-argument-hard-error-in-future... no
Building nokogiri using system libraries.
libxml2 version 2.6.21 or later is required!
*** 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
        --without-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/nyangry/.rbenv/versions/2.3.1/bin/$(RUBY_BASE_NAME)
        --help
        --clean
        --use-system-libraries
        --with-zlib-dir
        --without-zlib-dir
        --with-zlib-include
        --without-zlib-include=${zlib-dir}/include
        --with-zlib-lib
        --without-zlib-lib=${zlib-dir}/lib
        --with-xml2-dir
        --without-xml2-dir
        --with-xml2-include
        --without-xml2-include=${xml2-dir}/include
        --with-xml2-lib
        --without-xml2-lib=${xml2-dir}/lib
        --with-libxml-2.0-config
        --without-libxml-2.0-config
        --with-pkg-config
        --without-pkg-config
        --with-xslt-dir
        --without-xslt-dir
        --with-xslt-include
        --without-xslt-include=${xslt-dir}/include
        --with-xslt-lib
        --without-xslt-lib=${xslt-dir}/lib
        --with-libxslt-config
        --without-libxslt-config
        --with-exslt-dir
        --without-exslt-dir
        --with-exslt-include
        --without-exslt-include=${exslt-dir}/include
        --with-exslt-lib
        --without-exslt-lib=${exslt-dir}/lib
        --with-libexslt-config
        --without-libexslt-config

To see why this extension failed to compile, please check the mkmf.log which can be found here:

  /Users/nyangry/workspace/some_project/vendor/bundle/extensions/x86_64-darwin-15/2.3.0-static/nokogiri-1.6.7.2/mkmf.log

extconf failed, exit code 1

Gem files will remain installed in /Users/nyangry/workspace/some_project/vendor/bundle/gems/nokogiri-1.6.7.2 for inspection.
Results logged to /Users/nyangry/workspace/some_project/vendor/bundle/extensions/x86_64-darwin-15/2.3.0-static/nokogiri-1.6.7.2/gem_make.out
An error occurred while installing nokogiri (1.6.7.2), and Bundler cannot continue.
Make sure that `gem install nokogiri -v '1.6.7.2'` succeeds before bundling.

libxml2 あたりっぽい・・・当然設定は

$ cat ~/.bundle/config
---
BUNDLE_BUILD__NOKOGIRI: "--use-system-libraries"
BUNDLE_BUILD__LIBV8: "--with-system-v8"
BUNDLE_PATH: vendor/bundle
BUNDLE_BIN: vendor/bundle_bin
BUNDLE_JOBS: '8'

$ cat .bundle/config
---
BUNDLE_DISABLE_SHARED_GEMS: true

で --use-system-libraries しているし、

$ brew list | grep lib
libevent
libiconv
libpng
libtiff
libtool
libxml2
libxslt

libxml2 も入っている。

いろいろ試して結局

 brew link --force libxml2

で解決。

少し前に El Capitan にアップデートした際にシンボリックリンク周りが壊れたっぽい。（アップデート /usr/local/ 周りが壊れるのはよくある・・）

何回も調べてしまう attribute? の定義箇所

Rails Rails

ここを見ると query methods と書かれているので、 https://github.com/rails/rails/blob/master/activerecord/lib/active_record/base.rb

  # == Attribute query methods
  #
  # In addition to the basic accessors, query methods are also automatically available on the Active Record object.
  # Query methods allow you to test whether an attribute value is present.
  # Additionally, when dealing with numeric values, a query method will return false if the value is zero.
  #
  # For example, an Active Record User with the <tt>name</tt> attribute has a <tt>name?</tt> method that you can call
  # to determine whether the user has a name:
  #
  #   user = User.new(name: "David")
  #   user.name? # => true
  #
  #   anonymous = User.new(name: "")
  #   anonymous.name? # => false

ここを見に行くとそれがある https://github.com/rails/rails/blob/master/activerecord/lib/active_record/attribute_methods/query.rb

Rails の save, destroy は自動的に transaction でラップされる

Rails 
save and destroy are automatically wrapped in a transaction

Both save and destroy come wrapped in a transaction that ensures that whatever you do in validations or callbacks will happen under its protected cover. So you can use validations to check for values that the transaction depends on or you can raise exceptions in the callbacks to rollback, including after_* callbacks.

As a consequence changes to the database are not seen outside your connection until the operation is complete. For example, if you try to update the index of a search engine in after_save the indexer won't see the updated record. The after_commit callback is the only one that is triggered once the update is committed. See below.

ref: ActiveRecord::Transactions::ClassMethods

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