Ruby’s Magical case Statement

Ruby’scase Statement

by Tim Moore

Ruby’s Magicalcase Statement

by Tim Moore

Magical

There is Totally

Such a Thing as Magic

def handle_response(http_response) case http_response.status when 200 handle_success(http_response) when 301 handle_redirect(http_response) when 302 handle_redirect(http_response) when 303 handle_redirect(http_response) when 307 handle_redirect(http_response) when 404 handle_not_found(http_response) else handle_unknown_error(http_response) end end


















def handle_response(http_response) case http_response.status when 200 handle_success(http_response) when 301, 302, 303, 307 handle_redirect(http_response) when 404 handle_not_found(http_response) else handle_unknown_error(http_response) end end

def handle_response(http_response) case http_response.status when 200 handle_success(http_response) when 301, 302, 303, 307 handle_redirect(http_response) when 404 handle_not_found(http_response) else handle_unknown_error(http_response) end end

def handle_response(http_response) case http_response.status when 200 handle_success(http_response) when 301, 302, 303, 307 handle_redirect(http_response) when 404 handle_not_found(http_response) when 400...500 handle_client_error(http_response) when 500...600 handle_server_error(http_response) else handle_unknown_error(http_response) end end

def nickname(first_name) case first_name when 'Abraham' nickname = 'Abe' when 'Abigail' nickname = 'Abby' when 'Christopher', 'Christian', 'Christina' nickname = 'Chris' # etc., etc. else nickname = first_name end nickname end













irb> nickname 'Christopher' => "Chris" irb> nickname 'Abigail' => "Abby" irb> nickname 'Christina' => "Chris" irb> nickname 'Fabio' => "Fabio"



def nickname(first_name) nickname = case first_name when 'Abraham' 'Abe' when 'Abigail' 'Abby' when 'Christopher', 'Christian', 'Christina' 'Chris' # etc., etc. else first_name end nickname end

def nickname(first_name) nickname = case first_name when 'Abraham' 'Abe' when 'Abigail' 'Abby' when 'Christopher', 'Christian', 'Christina' 'Chris' # etc., etc. else first_name end nickname end

def nickname(first_name) case first_name when 'Abraham' 'Abe' when 'Abigail' 'Abby' when 'Christopher', 'Christian', 'Christina' 'Chris' # etc., etc. else first_name end !end

class Color < Struct.new(:r,:g,:b) ! RED = Color.new( 0xFF, 0x00, 0x00 ) GREEN = Color.new( 0x00, 0xFF, 0x00 ) BLUE = Color.new( 0x00, 0x00, 0xFF ) CYAN = Color.new( 0x00, 0xFF, 0xFF ) MAGENTA = Color.new( 0xFF, 0x00, 0xFF ) YELLOW = Color.new( 0xFF, 0xFF, 0x00 ) !end

def primary?(color, mode) case color when Color::RED, Color::GREEN, Color::BLUE mode == :additive when Color::CYAN, Color::MAGENTA, Color::YELLOW mode == :subtractive else false end end

class Color < Struct.new(:r,:g,:b) ! RED = Color.new( 0xFF, 0x00, 0x00 ) GREEN = Color.new( 0x00, 0xFF, 0x00 ) BLUE = Color.new( 0x00, 0x00, 0xFF ) CYAN = Color.new( 0x00, 0xFF, 0xFF ) MAGENTA = Color.new( 0xFF, 0x00, 0xFF ) YELLOW = Color.new( 0xFF, 0xFF, 0x00 ) !end

def primary?(color, mode) case color when Color::RED, Color::GREEN, Color::BLUE mode == :additive when Color::CYAN, Color::MAGENTA, Color::YELLOW mode == :subtractive else false end end

irb> primary? Color::RED, :additive => true irb> primary? Color::RED, :subtractive => false irb> primary? Color::CYAN, :subtractive => true irb> primary? Color.new(0,0,255), :additive => true irb> primary? Color.new(0,127,255), :additive => false

def local_search(query) case query when String specs_by_name(query) when Gem::Dependency search_by_dependency(query) when Gem::Specification, RemoteSpecification, LazySpecification, EndpointSpecification search_by_spec(query) else raise "You can't search for #{query}." end end










def want_a_beer?(beer_type) case beer_type when /^Sierra Nevada|IPA/ :yes when /V(ictoria)? ?B(itter)?/, /Bud(weiser)?/ :no else :probably end end





irb> want_a_beer? 'Sierra Nevada Pale Ale' => :yes irb> want_a_beer? 'Sierra Nevada Torpedo IPA' => :yes irb> want_a_beer? 'Mountain Goat IPA' => :yes irb> want_a_beer? 'Victoria Bitter' => :no irb> want_a_beer? 'VB' => :no irb> want_a_beer? 'V Bitter' => :no irb> want_a_beer? 'Budweiser' => :no irb> want_a_beer? 'Bud' => :no irb> want_a_beer? 'Bud Light' => :no irb> want_a_beer? 'Coopers Pale Ale' => :probably irb> want_a_beer? 'Stella Artois' => :probably

class Color def more_blue? b > r && b > g end ! def more_red? r > b && r > g end ! def more_green? g > r && g > b end end

def describe_color(color) case color when proc {|color| color.more_blue? } "blueish" when proc {|color| color.more_red? } "reddish" when proc {|color| color.more_green? } "greenish" else "pretty" end end



irb> describe_color Color::RED => "reddish" irb> describe_color Color::GREEN => "greenish" irb> describe_color Color.new(0xCC,0x11,0xFF) => "blueish" irb> describe_color Color::CYAN => "pretty"




def describe_color(color) case color when :more_blue?.to_proc "blueish" when :more_red?.to_proc "reddish" when :more_green?.to_proc "greenish" else "pretty" end end

===“case equality operator”

===“threequals”

case object when case1 do_something when case2 do_another_thing else do_something_else end

object case1 do_something case2 do_another_thing else do_something_else end

!

if case1 === object do_something elsif case2 === object do_another_thing else do_something_else end

class Range def ===(value) self.include?(value) end end

class Module def ===(object) object.is_a?(self) end end

class Regexp def ===(string) if self =~ string true else false end end end

class Proc def ===(object) self.call(object) end end

class Object def ===(other) self == other end end

def somegem_adapter case OtherGem::VERSION when version("< 1.0") OtherGemAdapter::Prerelease.new when version([">= 1.0", "< 2.0"]) OtherGemAdapter::Version1x.new when version(">= 2.0") OtherGemAdapter::Current.new end end








class VersionMatcher < Struct.new(:operator, :req_version) def ===(version) case operator when "=" version == req_version when ">" version > req_version when "<" version < req_version when ">=" version >= req_version when "<=" version <= req_version else false end end end





class VersionMatcher::All < Struct.new(:version_matchers) ! def ===(version) version_matchers .all? {|matcher| matcher === version } end !end





def version(requirements) case requirements when String op, req_version = requirements.split VersionMatcher.new(op, req_version) when Array matchers = requirements.map {|r| version(r)} VersionMatcher::All.new(matchers) end end






def somegem_adapter case OtherGem::VERSION when VersionMatcher.new("<", "1.0") OtherGemAdapter::Prerelease.new when version([">= 1.0", "< 2.0"]) OtherGemAdapter::Version1x.new when version(">= 2.0") OtherGemAdapter::Current.new end end

def somegem_adapter case OtherGem::VERSION when VersionMatcher.new("<", "1.0") OtherGemAdapter::Prerelease.new when version([">= 1.0", "< 2.0"]) OtherGemAdapter::Version1x.new when version(">= 2.0") OtherGemAdapter::Current.new end end

def somegem_adapter case OtherGem::VERSION when VersionMatcher.new("<", "1.0") OtherGemAdapter::Prerelease.new when VersionMatcher::All.new([ version(">= 1.0"), version("< 2.0") ]) OtherGemAdapter::Version1x.new when version(">= 2.0") OtherGemAdapter::Current.new end end

def somegem_adapter case OtherGem::VERSION when VersionMatcher.new("<", "1.0") OtherGemAdapter::Prerelease.new when VersionMatcher::All.new([ version(">= 1.0"), version("< 2.0") ]) OtherGemAdapter::Version1x.new when version(">= 2.0") OtherGemAdapter::Current.new end end

def somegem_adapter case OtherGem::VERSION when VersionMatcher.new("<", "1.0") OtherGemAdapter::Prerelease.new when VersionMatcher::All.new([ VersionMatcher.new(">=", "1.0"), VersionMatcher.new("<" , "2.0") ]) OtherGemAdapter::Version1x.new when version(">= 2.0") OtherGemAdapter::Current.new end end

def somegem_adapter case OtherGem::VERSION when VersionMatcher.new("<", "1.0") OtherGemAdapter::Prerelease.new when VersionMatcher::All.new([ VersionMatcher.new(">=", "1.0"), VersionMatcher.new("<" , "2.0") ]) OtherGemAdapter::Version1x.new when version(">= 2.0") OtherGemAdapter::Current.new end end

def somegem_adapter case OtherGem::VERSION when VersionMatcher.new("<", "1.0") OtherGemAdapter::Prerelease.new when VersionMatcher::All.new([ VersionMatcher.new(">=", "1.0"), VersionMatcher.new("<" , "2.0") ]) OtherGemAdapter::Version1x.new when VersionMatcher.new(">=", "2.0") OtherGemAdapter::Current.new end end

def somegem_adapter case OtherGem::VERSION when VersionMatcher.new("<", "1.0") OtherGemAdapter::Prerelease.new when VersionMatcher::All.new([ VersionMatcher.new(">=", "1.0"), VersionMatcher.new("<" , "2.0") ]) OtherGemAdapter::Version1x.new when VersionMatcher.new(">=", "2.0") OtherGemAdapter::Current.new end end

def somegem_adapter OtherGem::VERSION VersionMatcher.new("<", "1.0") OtherGemAdapter::Prerelease.new VersionMatcher::All.new([ VersionMatcher.new(">=", "1.0"), VersionMatcher.new("<" , "2.0") ]) OtherGemAdapter::Version1x.new VersionMatcher.new(">=", "2.0") OtherGemAdapter::Current.new end end

def somegem_adapter ! if VersionMatcher.new("<", "1.0") \ === OtherGem::VERSION OtherGemAdapter::Prerelease.new elsif VersionMatcher::All.new([ VersionMatcher.new(">=", "1.0"), VersionMatcher.new("<" , "2.0") ]) \ === OtherGem::VERSION OtherGemAdapter::Version1x.new elsif VersionMatcher.new(">=", "2.0") \ === OtherGem::VERSION OtherGemAdapter::Current.new end !end

def somegem_adapter ! if VersionMatcher.new("<", "1.0") \ === OtherGem::VERSION OtherGemAdapter::Prerelease.new elsif VersionMatcher::All.new([ VersionMatcher.new(">=", "1.0"), VersionMatcher.new("<" , "2.0") ]) \ === OtherGem::VERSION OtherGemAdapter::Version1x.new elsif VersionMatcher.new(">=", "2.0") \ === OtherGem::VERSION OtherGemAdapter::Current.new end !end

irb> OtherGem::VERSION = '0.9' irb> somegem_adapter => #<OtherGemAdapter::Prerelease> irb> OtherGem::VERSION = '1.0' irb> somegem_adapter => #<OtherGemAdapter::Version1x> irb> OtherGem::VERSION = '1.2' irb> somegem_adapter => #<OtherGemAdapter::Version1x> irb> OtherGem::VERSION = '2.0' irb> somegem_adapter => #<OtherGemAdapter::Current> irb> OtherGem::VERSION = '4.0' irb> somegem_adapter => #<OtherGemAdapter::Current>

Thank you!

Ruby’s Magical case Statement

Technology