Hi,
I am working in an application and I need to store my own objects in
some collections. I was using instances of Array to store that objects,
but now, I need not to store duplicated instances. Searching the Web I
found de class ‘Set’, which seems to do that. I also read that with this
collection you have to override the eql? and hash methods in your
classes objects to set a criteria to compare you objects.
I will try to explain better myself with an example:
I have the following class Track
class Track < ActiveRecord::Base
belongs_to :album
def hash
StringUtils.nice_slug(self.name, “false”).hash
end
def eql?(other)
equal = false
if StringUtils.nice_slug(self.name, “false”).downcase.eql?
StringUtils.nice_slug(other.name, “false”).downcase
equal = true
end
equal
end
end
Now, I create two instances of Track and two of Set, and I insert one
track into each Set.
a = Set::new
t1 = Track.new
=> #<Track id: nil, name: nil, lyric: nil, created_at: nil, updated_at:
nil>
t1.name = “Gracias por elegirme”
t2 = Track.new
=> #<Track id: nil, name: nil, lyric: nil, created_at: nil, updated_at:
nil>
t2.name = “Gracias Por Elegirme”
a << t1
=> #<Set: {#<Track id: nil, name: “Gracias por elegirme”, lyric: nil,
created_at: nil, updated_at: nil>}>
b = Set::new
b << t2
#<Set: {#<Track id: nil, name: “Gracias Por Elegirme”, lyric: nil,
created_at: nil, updated_at: nil>}>
And finally, I try to insert the content of b into a:
a.merge(b)
The result that I am expecting is that nothing is inserted into a
because the name of the two tracks is very similar, and when we convert
into downcase the are equal (“gracias por elegirme”).
But instead I get the following:
#<Set: {#<Track id: nil, name: “Gracias Por Elegirme”, lyric: nil,
created_at: nil, updated_at: nil>, #<Track id: nil, name: “Gracias por
elegirme”, lyric: nil, created_at: nil, updated_at: nil>}>
Now a stores the two Track instances.
I would appreciate so much your help.