gem install pg not working on Mac El Capitan

Question

I tried to install pg Gem on Mac El Capitan, but I always get this error:

    Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.

        /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby extconf.rb --with-pg-config=/Users/ricardolopes/Developer/homebrew/bin/pg_config
    Using config values from /Users/ricardolopes/Developer/homebrew/bin/pg_config
    checking for libpq-fe.h... yes
    checking for libpq/libpq-fs.h... yes
    checking for pg_config_manual.h... yes
    checking for PQconnectdb() in -lpq... no
    checking for PQconnectdb() in -llibpq... no
    checking for PQconnectdb() in -lms/libpq... no
    Can't find the PostgreSQL client library (libpq)
    *** 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=/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby
        --with-pg
        --without-pg
        --enable-windows-cross
        --disable-windows-cross
        --with-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}/
        --with-pqlib
        --without-pqlib
        --with-libpqlib
        --without-libpqlib
        --with-ms/libpqlib
        --without-ms/libpqlib


    Gem files will remain installed in /Users/ricardolopes/Code/site-noticias/vendor/bundle/ruby/2.0.0/gems/pg-0.18.3 for inspection.
    Results logged to /Users/ricardolopes/Code/site-noticias/vendor/bundle/ruby/2.0.0/gems/pg-0.18.3/ext/gem_make.out
    An error occurred while installing pg (0.18.3), and Bundler cannot continue.
    Make sure that gem install pg -v '0.18.3' succeeds before bundling.

I also tried:

ARCHFLAGS="-arch x86_64" gem install pg

When I tried it I got:

    Building native extensions.  This could take a while...
    Successfully installed pg-0.18.3
    invalid options: -f fivefish
    (invalid options are ignored)
    Parsing documentation for pg-0.18.3
    Done installing documentation for pg after 3 seconds
    1 gem installed

But I run bundle install and get the same error posted in the beginning of this post.

I tried reinstall PostgresSQL from brew.

Answer 1

Try this:

• brew update
• brew install postgresql
• sudo gem install pg -v 'VERSION'

Answer 2

This worked for me:
sudo gem install pg -- --with-pg-config=/Applications/Postgres.app/Contents/Versions/9.4/bin/pg_config

Remember to change 9.4 to your postgres version, if different from 9.4.