Notes on the Le Wagon Regular Expressions Provider Grouping exercise
Let’s say you have a user database with thousands of emails, and you want to analyze them according to their provider.
We can write a method which will group differnent emails by provider and also a method that will return emails of a certain provider.
MAIL_REGEX = /@(?<domain>[^\.]+)\./ def group_mails(emails) # TODO: group email by provider emails.select do |email| MAIL_REGEX.match(email) end emails.group_by do |email| MAIL_REGEX.match(email)[:domain] end end
To start we need to make a regex that will check to see if the email is valid. We have also specified a goup name of
<domain>. This refers to the group inside the
(). This will match any string with
@then any characters and a
We define a method of
group_mailswhich takes one parameter of
Now, we can iterate over the emails given to us as an argument using
.select. This will return an array containing all the elements which match the criteria. In this case we call
MAIL_REGEXand pass it an argument of
We then perform a second iteration using
.group_by. This will return a hash where the keys are the result from executing the block and the values are arrays of elements that correspond to each key. In other words the keys will be the domain names and the values are the array of elements which match the domain name.
def provider?(email, provider) # TODO: return true if email is of given provider match = MAIL_REGEX.match(email) if match[:domain] == provider return true else return false end end
To return true if an email is of a given provider, we can define a new method of
provider? and this willtake two arguments; an
Firstly, we assign the result of calling
MAIL_REGEXto the variable
We can then say if its true that the domain part of the regex matches the provider then return true. However, if not then it returns false.