comparing objects
in [Ruby]
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From: Anderson Leite on 3 Jun 2010 18:29 How can I compare two objects and get true if some of his atributes are equals ? I need to compare two arrays of users, and get and third array just with the matches. I found the "&" method that work for Fixnuns and String, but...how to use with objects ? class User attr_accessor :email end a = User.new a.email = 'ruby(a)rails.com' b = User.new b.email = 'ruby(a)rails.com' array_one = [a] array_two = [b] array_three = array_one & array_two puts array_three # I want the user here Can you help me ? thanks -- Posted via http://www.ruby-forum.com/.
From: Marcin Wolski on 3 Jun 2010 21:41 Anderson Leite wrote: > How can I compare two objects and get true if some of his atributes are > equals ? > > I need to compare two arrays of users, and get and third array just with > the matches. I found the "&" method that work for Fixnuns and String, > but...how to use with objects ? > > > class User > attr_accessor :email > end > > a = User.new > a.email = 'ruby(a)rails.com' > > b = User.new > b.email = 'ruby(a)rails.com' > > array_one = [a] > array_two = [b] > > > array_three = array_one & array_two > > puts array_three # I want the user here > > > > Can you help me ? > thanks I think you need to define how to compare your objects and their hash. Have a look below. class User attr_accessor :email def ==(other) @email == other.email end alias eql? == def hash code = 17 code = 37*code + @email.hash end def to_s "#@email" end end a = User.new a.email = 'ruby(a)rails.com' c = User.new c.email = 'groovy(a)rails.com' b = User.new b.email = 'ruby(a)rails.com' d = User.new d.email = 'c++(a)rails.com' d = User.new d.email = 'python(a)rails.com' array_one = [a,d] array_two = [b, c] array_three = array_one & array_two puts array_three # I want the user here #prints ruby(a)rails.com -- Posted via http://www.ruby-forum.com/.
From: Robert Dober on 4 Jun 2010 04:02 On Fri, Jun 4, 2010 at 3:41 AM, Marcin Wolski <wolskint(a)o2.pl> wrote: <snip> > def ==(other) > @email == other.email > end this seems ok > > alias eql? == > > def hash > code = 17 > code = 37*code + @email.hash > end > Are you sure you want to do this? "equal" objects would overwrite each other when used as hash keys. This is normally not a good idea, be sure you really want/need this! R -- The best way to predict the future is to invent it. -- Alan Kay
From: Marcin Wolski on 4 Jun 2010 04:16 Robert Dober wrote: > On Fri, Jun 4, 2010 at 3:41 AM, Marcin Wolski <wolskint(a)o2.pl> wrote: > <snip> >> �def ==(other) >> �@email == other.email >> �end > this seems ok >> >> �alias eql? == >> >> �def hash >> � �code = 17 >> � �code = 37*code + @email.hash >> end >> > Are you sure you want to do this? "equal" objects would overwrite each > other when used as hash keys. This is normally not a good idea, be > sure you really want/need this! > R What would be the other possible solution to this problem? The example code will not work without overwritten eql? and hash methods. -- Posted via http://www.ruby-forum.com/.
From: Robert Dober on 4 Jun 2010 05:31
On Fri, Jun 4, 2010 at 10:16 AM, Marcin Wolski <wolskint(a)o2.pl> wrote: > Robert Dober wrote: >> On Fri, Jun 4, 2010 at 3:41 AM, Marcin Wolski <wolskint(a)o2.pl> wrote: >> <snip> >>> �def ==(other) >>> �@email == other.email >>> �end >> this seems ok >>> >>> �alias eql? == >>> >>> �def hash >>> � �code = 17 >>> � �code = 37*code + @email.hash >>> end >>> >> Are you sure you want to do this? "equal" objects would overwrite each >> other when used as hash keys. This is normally not a good idea, be >> sure you really want/need this! >> R > > What would be the other possible solution to this problem? The example > code will not work without overwritten eql? and hash methods. > -- > Posted via http://www.ruby-forum.com/. > Does it not? Seems to work on my box class A def == other true end end # class A a1 = A::new a2 = A::new a3 = A::new p [a1,a2] & [a1,a3] -- The best way to predict the future is to invent it. -- Alan Kay |