The group_by Method Stops Underage Drinking

Because sometimes you blog about Ruby on a Saturday night

February 7th, 2015 : 4 minutes

I am going to explain how to use the group_by method the way I wished it was explained to me.

group_by is a method that...

  1. - can be used to group integers or strings
  2. - is called by either an array or hash
  3. - is more powerful when followed by a block specifying how the user wants to group information

Example #1 : An array of integers

I have an array of all the ages of my team members. I want to do a bar crawl but everyone old enough?

You can see that I've called the group_by method on my array of ages. The block that I've passed looks for ages that are old enough to (legally) drink, and you can see group_by has separated the ages by those that pass true and false in the block.

Example #1 (continued): An array of integers + group labels

You can also specify how you'd like to label each group by editing the block. Below, I am using the exact same array as before but replacing "true" and "false" with "Party Peoples!" and "Too Young..." respectively.

Example #2 : A hash with strings and integers

So now I know that 2 of my teammates can't go to the bars with me, but...who are they? Below, I've created a hash with the names of the people whose ages we were previously looking at.

I can call the group_by method to my hash just like I did with my array to get the names of my underaged friends. (Maybe I shouldn't even bother inviting them.)

Example #2 (continued) : A hash with strings and integers + randomly assigning groups

After much'd be really sad for Abbey and Emerson to not be able to join us simply because of their age. So instead, why don't I just host something at my place? I'll provide the drinks and people can bring whatever they want. Or better yet! I can randomly group them to bring chasers and snacks.

I hope that helps explain how the group_by method works. Let me know if I missed something or if anything was confusing!