2012/10/1 John Merlino <stoici...@aol.com> > I know that Struct class defines the [] instance method: > > 1.9.3p0 :014 > Struct.instance_methods(false) > => > [:==, :eql?, :hash, :inspect, :to_s, :to_a, :values, :size, :length, > :each, :each_pair, : > [], : > []=, :select, :values_at, :members, :pretty_print, :pretty_print_cycle, > :as_json] > > This allows you to mimic hash behavior via Struct: > > 1.9.3p0 :016 > HashLike = Struct.new(:x,:y) > => HashLike > 1.9.3p0 :017 > h = HashLike.new(1,2) > => #<struct HashLike x=1, y=2> > 1.9.3p0 :018 > h[:x] > => 1 > 1.9.3p0 :019 > h[:y] = 100 > => 100 > > But I come across a use case where the square brackets method was used > as instantiation: > > 1.9.3p0 :001 > Point = Struct.new :x, :y do > 1.9.3p0 :002 > def distance(point) > 1.9.3p0 :003?> Math.sqrt((point.x - self.x) ** 2 + > 1.9.3p0 :004 > (point.y - self.y) ** 2) > 1.9.3p0 :005?> end > 1.9.3p0 :006?> end > => Point > 1.9.3p0 :007 > Point[3,4].distance Point[0,0] > => 5.0 > > That confuses me. How can [] be used both as both hash key accessors > and also instantiation (e.g. new)? > > -- > You received this message because you are subscribed to the Google Groups > "Ruby on Rails: Talk" group. > To post to this group, send email to rubyonrails-talk@googlegroups.com. > To unsubscribe from this group, send email to > rubyonrails-talk+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/groups/opt_out. > > > That's because the :[] method is both defined as an instance method and as a class method of the Point class.
>Point.singleton_class.instance_methods false => [:new, :[], :members] -- Piantanida, Ignacio Julián -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk@googlegroups.com. To unsubscribe from this group, send email to rubyonrails-talk+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
