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# response to http://jumpstartlab.com/news/archives/2013/04/23/the-death-of-ifs | |
#----------------- | |
# Commands : | |
#----------------- | |
class Command | |
class Quit ; def execute ; exit end end | |
class Invalid ; def execute ; puts 'invalid command' end end | |
class Tweeting ; def execute ; puts "tweeting" end end | |
class Retweeting ; def execute ; puts "retweeting" end end | |
class Commenting ; def execute ; puts "commenting" end end | |
end | |
#---------------------------------- | |
# Mapping : input -> 1 Command | |
#---------------------------------- | |
class Commands | |
MAPPING = Hash.new{ Command::Invalid.new } | |
def self.register(input, command) | |
MAPPING[input] = command | |
end | |
def self.command_for(input) | |
MAPPING[input] | |
end | |
def self.valid_inputs | |
MAPPING.keys | |
end | |
end | |
Commands.register 'q', Command::Quit.new | |
Commands.register 't', Command::Tweeting.new | |
Commands.register 'r', Command::Retweeting.new | |
Commands.register 'c', Command::Commenting.new | |
#---------------------------------- | |
# main loop | |
#---------------------------------- | |
def show_prompt | |
puts "Enter a command (one of #{Commands.valid_inputs.join(', ')})" ; true | |
end | |
while show_prompt && command = Commands.command_for(STDIN.gets.chomp) | |
command.execute | |
end | |
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#---------------------------------- | |
# test input -> command mapping | |
#---------------------------------- | |
def assert(condition) raise unless condition end | |
assert Commands.command_for('q').is_a?(Command::Quit) | |
assert Commands.command_for('t').is_a?(Command::Tweeting) | |
assert Commands.command_for('r').is_a?(Command::Retweeting) | |
assert Commands.command_for('c').is_a?(Command::Commenting) | |
assert Commands.command_for('?').is_a?(Command::Invalid) | |
assert Commands.command_for(' ').is_a?(Command::Invalid) | |
#---------------------------------- | |
# test individual commands effect | |
#---------------------------------- | |
require 'stringio' | |
def assert_output_is(expected) | |
$stdout = StringIO.new | |
yield | |
unless expected == (actual_result = $stdout.string.chomp) | |
raise "incorrect output : \n\texpected : #{expected} \n\tfound : #{actual_result}" | |
end | |
ensure | |
$stdout = STDOUT | |
end | |
assert_output_is("tweeting" ) { Command::Tweeting .new.execute } | |
assert_output_is("retweeting" ) { Command::Retweeting.new.execute } | |
assert_output_is("commenting" ) { Command::Commenting.new.execute } | |
assert_output_is("invalid command") { Command::Invalid .new.execute } | |
begin | |
Command::Quit.new.execute | |
rescue SystemExit | |
system_exit_triggered = true | |
ensure | |
raise "Quit didn't exit" unless system_exit_triggered | |
end |
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I like it.