example_query.rb

This example demonstrates how use the standard Query classes.

00001 #!/usr/bin/env ruby
00002 # vim: set sw=4 sts=4 et tw=100 :
00003 
00004 =begin description
00005 This example demonstrates how use the standard Query classes.
00006 =end
00007 
00008 require 'Paludis'
00009 require 'example_command_line'
00010 
00011 include Paludis
00012 
00013 # Run a query, and show its results.
00014 def show_query(env, query)
00015     # Queries support a crude form of stringification.
00016     puts "#{query}:"
00017 
00018     # Usually the only thing clients will do with a Query object is pass it to
00019     # PackageDatabase#query.
00020     ids = env.package_database.query(query, QueryOrder::OrderByVersion)
00021 
00022     # Show the results
00023     ids.each do | id |
00024         puts "    #{id}"
00025     end
00026     puts
00027 end
00028 
00029 # We start with an Environment, respecting the user's '--environment' choice.
00030 env = EnvironmentMaker.instance.make_from_spec(ExampleCommandLine.instance.environment)
00031 
00032 # Make some queries, and display what they give.
00033 show_query(env, Query::Matches.new(Paludis::parse_user_package_dep_spec("sys-apps/paludis", [])))
00034 
00035 # Queries can be combined. The resulting query is optimised internally,
00036 # potentially giving better performance than doing things by hand.
00037 show_query(env,
00038            Query::Matches.new(Paludis::parse_user_package_dep_spec("sys-apps/paludis", [])) &
00039            Query::SupportsInstalledAction.new)
00040 
00041 # Usually Query::NotMasked should be combined with Query::SupportsInstallAction,
00042 # since installed packages aren't masked.
00043 show_query(env,
00044            Query::Matches.new(Paludis::parse_user_package_dep_spec("sys-apps/paludis", [])) &
00045            Query::SupportsInstallAction.new &
00046            Query::NotMasked.new)
00047