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继Tony Coconate的Rails + Ember.js (with the Ember CLI)教程，我们正在尝试创建一个新的Rails API。安装pg（0.18.2）时发生错误，并且Bundler无法继续
当我们运行rails new api -T -d postgresql，我们得到了以下错误消息：
An error occurred while installing pg (0.18.2), and Bundler cannot continue.
Make sure that `gem install pg -v '0.18.2'` succeeds before bundling.
这就是Gemfile文件看起来像：
source "https://rubygems.org"
gem "rails", "4.2.1"
gem "activeadmin", github: "gregbell/active_admin" # Until it"s 1.0.0
gem "coffee-rails", "~> 4.0.0"
gem "devise"
gem "grape"
gem "grape-active_model_serializers"
gem "grape-swagger-rails"
gem "jquery-rails"
gem "pg"
gem "rack-cors", require: "rack/cors"
gem "sass-rails", "~> 4.0.3"
gem "uglifier", ">= 1.3.0"
group :development do
gem "better_errors"
gem "meta_request"
gem "quiet_assets"
gem "spring"
end
group :development, :test do
gem "capybara"
gem "capybara-screenshot"
gem "database_cleaner"
gem "factory_girl_rails"
gem "faker"
gem "poltergeist"
gem "pry-nav"
gem "pry-rails"
gem "pry-stack_explorer"
gem "pry-theme"
gem "rspec-rails"
gem "rubocop"
gem "shoulda-matchers"
gem "spring-commands-rspec"
end
当我们运行bundle install，我们得到了以下错误消息：
Gem::Ext::BuildError: ERROR: Failed to build gem native extension.
/Users/user_name/.rvm/rubies/ruby-2.2.1/bin/ruby -r ./siteconf20150629-73521-9m0ocx.rb extconf.rb
checking for pg_config... no
No pg_config... trying anyway. If building fails, please try again with
--with-pg-config=/path/to/pg_config
checking for libpq-fe.h... no
Can't find the 'libpq-fe.h header
*** 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/user_name/.rvm/rubies/ruby-2.2.1/bin/$(RUBY_BASE_NAME)
--with-pg
--without-pg
--enable-windows-cross
--disable-windows-cross
--with-pg-config
--without-pg-config
--with-pg_config
--without-pg_config
--with-pg-dir
--without-pg-dir
--with-pg-include
--without-pg-include=${pg-dir}/include
--with-pg-lib
--without-pg-lib=${pg-dir}/lib
extconf failed, exit code 1
Gem files will remain installed in /Users/user_name/.rvm/gems/ruby-2.2.1/gems/pg-0.18.2 for inspection.
Results logged to /Users/user_name/.rvm/gems/ruby-2.2.1/extensions/x86_64-darwin-14/2.2.0-static/pg-0.18.2/gem_make.out
An error occurred while installing pg (0.18.2), and Bundler cannot continue.
Make sure that `gem install pg -v '0.18.2'` succeeds before bundling.
当我们运行gem install pg -v '0.18.2'，我们还得到一个错误：
Building native extensions. This could take a while...
ERROR: Error installing pg:
ERROR: Failed to build gem native extension.
/Users/user_name/.rvm/rubies/ruby-2.2.1/bin/ruby -r ./siteconf20150629-73553-uaymt5.rb extconf.rb
checking for pg_config... no
No pg_config... trying anyway. If building fails, please try again with
--with-pg-config=/path/to/pg_config
checking for libpq-fe.h... no
Can't find the 'libpq-fe.h header
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers. Check the mkmf.log file for more details. You may
need configuration options.
Provided configuration options:
--with-opt-dir
--without-opt-dir
--with-opt-include
--without-opt-include=${opt-dir}/include
--with-opt-lib
--without-opt-lib=${opt-dir}/lib
--with-make-prog
--without-make-prog
--srcdir=.
--curdir
--ruby=/Users/user_name/.rvm/rubies/ruby-2.2.1/bin/$(RUBY_BASE_NAME)
--with-pg
--without-pg
--enable-windows-cross
--disable-windows-cross
--with-pg-config
--without-pg-config
--with-pg_config
--without-pg_config
--with-pg-dir
--without-pg-dir
--with-pg-include
--without-pg-include=${pg-dir}/include
--with-pg-lib
--without-pg-lib=${pg-dir}/lib
extconf failed, exit code 1
Gem files will remain installed in /Users/user_name/.rvm/gems/ruby-2.2.1/gems/pg-0.18.2 for inspection.
Results logged to /Users/user_name/.rvm/gems/ruby-2.2.1/extensions/x86_64-darwin-14/2.2.0-static/pg-0.18.2/gem_make.out
的什么是错的，而最重要的是，我们如何解决这个问题的任何想法？