Array help needed

[Zouplaz]

Hello, sorry if this question is stupid but I can’t find a solution
after several readings about Arrays

Array ‘a’ contains several objets (ruby classes instances), each
instance have an id property

I need a clean solution to return true if array ‘a’ contains an instance
with id foo without iterating the whole array.

Example

def add_user(user)
unless users.include?(user.id)
users << user
end
end

users.include? statement is wrong because we compare id’s with objects.
Which is the right way to do it ?

Thanks

[Zouplaz]

On Tue, Feb 26, 2008 at 3:20 PM, Zouplaz [email protected] wrote:

Example

def add_user(user)

• unless users.include?(user.id)

• unless users.any? {|u| user.id == u.id }

[Zouplaz]

On Tue, Feb 26, 2008 at 9:36 AM, Jano S. [email protected]
wrote:

with id foo without iterating the whole array.

Example

def add_user(user)

• unless users.include?(user.id)

• unless users.any? {|u| user.id == u.id }

 users << user

end
end

If you can’t do this

def add_user(user)
unless users.include?(user) # just check the user instead of the id
users << user
end
end

then I’d also recommend Jano’s solution.

Regards,
Craig

[Zouplaz]

2008/2/26, Jano S. [email protected]:

Example

def add_user(user)

• unless users.include?(user.id)

• unless users.any? {|u| user.id == u.id }

 users << user

end
end

For a more efficient solution use a Hash:

def add_user(user)
@users[user.id] ||= user
end

def users
@users.values
end

Kind regards

robert

[Zouplaz]

On 2/26/08, Christopher S. [email protected] wrote:

end

Christopher

Additionally, if a unique user always has the same id (for instance,
they’re defined in a database and the id is the primary key), then you
can override #== in your class to compare ids to determine equality.
Then you can just call #include? with the user directly:

def add_user(user)
unless users.include?(user)
users << user
end
end

This is almost definitely the most efficient solution, but it does
require you to modify your class.

Best,
Christopher

[Zouplaz]

le 26/02/2008 15:36, Jano S. nous a dit:

def add_user(user)

• unless users.include?(user.id)

• unless users.any? {|u| user.id == u.id }

 users << user

end
end

Fine ! This is was I was looking for.

Thanks to people who answered…

[Zouplaz]

On 2/26/08, Zouplaz [email protected] wrote:

Example

def add_user(user)
unless users.include?(user.id)
users << user
end
end

users.include? statement is wrong because we compare id’s with objects.
Which is the right way to do it ?

Read up on the Enumerable module.
module Enumerable - RDoc Documentation.

You have a couple of options. The simplest code-wise is to use find:

def add_user(user)
unless users.find { |u| u.id == user.id }
users << user
end
end

Potentially marginally more efficient is #map and then calling
#include? on the result

def add_user(user)
unless users.map { |u| u.id }.include?(user.id)
users << user
end
end

Christopher