我已经按照所示安装了pg gem，但是...
Building native extensions. This could take a while...
Successfully installed pg-0.11.0
ERROR: Could not find a valid gem '—' (>= 0) in any repository
ERROR: Could not find a valid gem '–with-pg-config=/usr/local/pg/bin/pg_config' (>= 0) in any repository
1 gem installed
Installing ri documentation for pg-0.11.0...
Installing RDoc documentation for pg-0.11.0...
当我运行bundle install时，出现了一些奇怪的情况，pg gem无法完全安装：
Fetching source index for http://rubygems.org/
Using rake (0.9.2)
Using abstract (1.0.0)
Using activesupport (3.0.10)
Using builder (2.1.2)
Using i18n (0.5.0)
Using activemodel (3.0.10)
Using erubis (2.6.6)
Using rack (1.2.3)
Using rack-mount (0.6.14)
Using rack-test (0.5.7)
Using tzinfo (0.3.29)
Using actionpack (3.0.10)
Using mime-types (1.16)
Using polyglot (0.3.2)
Using treetop (1.4.10)
Using mail (2.2.19)
Using actionmailer (3.0.10)
Using arel (2.0.10)
Using activerecord (3.0.10)
Using activeresource (3.0.10)
Using annotate (2.4.0)
Using bundler (1.0.18)
Using diff-lcs (1.1.2)
Using factory_girl (1.3.3)
Using rdoc (3.9.3)
Using thor (0.14.6)
Using railties (3.0.10)
Using rails (3.0.10)
Using factory_girl_rails (1.0)
Using faker (0.3.1)
Using gravatar_image_tag (1.0.0.pre2)
Using nokogiri (1.5.0)
Installing pg (0.11.0) with native extensions /Users/******/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/site_ruby/1.9.1/rubygems/installer.rb:552:in `rescue in block in build_extensions': ERROR: Failed to build gem native extension. (Gem::Installer::ExtensionBuildError)
然后我会看到一些提示信息，告诉我可能缺少必要的库或头文件：
*** 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/TonyNg/.rvm/rubies/ruby-1.9.2-p180/bin/ruby
--with-pg
--without-pg
--with-pg-dir
--without-pg-dir
--with-pg-include
--without-pg-include=${pg-dir}/include
--with-pg-lib
--without-pg-lib=${pg-dir}/lib
--with-pg-config
extconf.rb:24:in ``': No such file or directory - /users/****/
这是我的 Gem 文件：
source 'http://rubygems.org'
gem 'rails', '3.0.10'
# Bundle edge Rails instead:
# gem 'rails', :git => 'git://github.com/rails/rails.git'
gem 'pg'
gem 'gravatar_image_tag', '1.0.0.pre2'
gem 'will_paginate', '3.0.pre2'
group :development do
gem 'rspec-rails', '2.6.1'
gem 'annotate', '2.4.0'
gem 'faker', '0.3.1'
end
group :test do
gem 'rspec-rails', '2.6.1'
gem 'webrat', '0.7.1'
gem 'spork', '0.9.0.rc8'
gem 'factory_girl_rails', '1.0'
end
# Use unicorn as the web server
# gem 'unicorn'
# Deploy with Capistrano
# gem 'capistrano'
# To use debugger (ruby-debug for Ruby 1.8.7+, ruby-debug19 for Ruby 1.9.2+)
# gem 'ruby-debug'
# gem 'ruby-debug19', :require => 'ruby-debug'
# Bundle the extra gems:
# gem 'bj'
# gem 'nokogiri'
# gem 'sqlite3-ruby', :require => 'sqlite3'
# gem 'aws-s3', :require => 'aws/s3'
# Bundle gems for the local environment. Make sure to
# put test-only gems in this group so their generators
# and rake tasks are available in development mode:
# group :development, :test do
# gem 'webrat'
# end
我该如何解决这个问题？提前感谢您。
编辑 答案：关键是要安装pg gem到正确的路径下，而之前它没有完全安装。我在我的最后一条评论中运行了 'gem install pg -- --with-pg-config=/opt/local/lib/postgresql84/bin/pg_config' ，针对我所提供的路径。我只需要找到我的pg_config文件并在其中运行gem install。
mkmf.log文件中有什么信息呢？ - mu is too short