Some help with a simple Rails problem?

rubyonrails-talk
1

Hi Guys. Im new to Rails, after developing in Java for about the last 4 years, because I want to develop better web based apps and find Ruby would be better for this. Basically im learning as I'm going and what I want to be able to do is:

Say I have created a 'user' model (storing a id, name and email), a 'society' model (imagine club/societies at a school so it would have a society's name and code) and another model joining every user to a club (i.e. user.id = society.id) all stored in a database. How would I, given a society's id, generate an array of all the names and email address of users belonging to it to then send an email on to each?

If you could help me solve this basic problem it would be fantastic as I know seeing the code on how it is done will give me a resource do many of the things I want to be able to do.

2

Let's say you've set up your models like this:

class User < ActiveRecord::Base   has_many :memberships end

class Membership < ActiveRecord::Base   belongs_to :user   belongs_to :society end

class Society < ActiveRecord::Base   has_many :memberships end

Then, if you have the id of a society, this is the kind of thing you're trying to get

@society = Society.find(id) @memberships = @society.memberships @users = @memberships.map{|m| m.user}

The Ruby #map method on an array goes through each item in the array, runs the code you specify (in this case, m.user to return the user for that membership), and puts the results into a new array. Thus you now have an array of the users who are members of that society.

For brevity, you could collapse that down to:

@users = Society.find(id).memberships.map{|m| m.user}

However, as a nicer alternative, the ActiveRecord 'has_many' accepts a :through parameter, that lets you 'reach through' associations automatically. So, if you amended your Society class to:

class Society < ActiveRecord::Base   has_many :memberships   has_many :users, :through => :memberships end

then you can just do:

@users = Society.find(id).users

and it should work.

Then, sending the emails. You'd probably set up a mailer that just takes a User object as a parameter; something like:

class SocietyMailer < ActionMailer::Base   def notification_email(user)     recipients user.email     body {:user => user}   end end

You then have a 'user' variable in the email template, which you can use to customise the email.

With that in place, you can send an email to each member with something like:

@users.each{|u| SocietyMailer.deliver_notification_email(u)}

For more on mailers, see the guide:

and for the has_many... :through construction, see:

http://guides.rubyonrails.org/association_basics.html#the-has-many-through-association

Chris

3

Nice response, Chris. Exemplary. Bravo!

Best regards, Bill

4

Chris, I am absolutely blown away at your response. Here I was thinking I would just get some guidance and you come back with an absolutely flawless reply (really going above and beyond the call of duty). Thank you SO much!! I will give it a go and I'm sure it will all work.

An absolutely brilliant gesture that shows me the Ruby community is the one to be part of.

Thanks again,

Nick

5

I would also suggest that you go to http://guides.rubyonrails.org/ and read the guides there. I am sure you will find them very helpful.

Colin