Ruby/Rails - Nested blocks without hitting the DB everytime?

Question

Not exactly sure how to look this up, but I'm not finding the solution anywhere. I want to assign an array of users an array of websites. Like so:

users = User.all
sites = Site.all

users.each do |user|
  sites.each do |site|
     user.websites << site
  end
end

Obviously, this does not work because I'm missing something about block scope. However, this works:

users.each do |user|
  Site.all.each do |site|
    user.websites << site
  end
end

But I'm trying to eliminate the extra calls to the DB (Site.all.each ...) and learn something about Ruby in the process. Any help is greatly appreciated.

Maybe I am missing something, but why does the first way not work, what is the error message? — user120587
– user120587, Commented Oct 25, 2009 at 6:45

Harpastum · Accepted Answer · 2009-10-25 07:18:58Z

1

I'm not sure why the first attempt wouldn't work, but I also don't really understand why you'd append each site separately. Wouldn't this work?

users = User.all
sites = Site.all

users.each do |user|
    user.websites.concat(sites)
end

ruby-doc link to concat

If they're actually hashes (although you say they're arrays), the method you're looking for is merge

answered Oct 25, 2009 at 7:18

Harpastum

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Comments

EmFi · Accepted Answer · 2009-10-25 20:49:17Z

0

If your User model is in a has many relationship with Websites (classname Sites), then you can just do

users = User.all
sites = Site.all

users.each do |user|
  user.websites = sites
end

Edit: For Harpastum:

If user.websites contains items not in Site.all that you don't want over written the following works.

users = User.all
sites = Site.all

users.each do |user|
  user.websites << sites
end

edited Oct 25, 2009 at 20:49

answered Oct 25, 2009 at 7:52

EmFi

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3 Comments

Harpastum Over a year ago

I'm new to rails, but wouldn't that set the value of user.websites to just the new array? i.e. Wouldn't any previous records in user.websites get overwritten?

EmFi Over a year ago

Yes. But, it wouldn't matter given the assumption of a has_many relationship. There could be no items in websites that don't exist in Site.all

user188241 Over a year ago

Thanks once again, EmFi. You're a big help.

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