Ruby-function for reading, parsing a text-file, removing data-duplicates

Question

Task description: Implement a generate_unique_phone_numbers function. The function shall parse the given text-file.

Content-example:

Trinidad Kemp,[phone]
Noel Bush,[phone]
Claudette Davila,[phone]
Shaun Mcbride,[phone]
Katy Blanchard,[phone]
...

Then return a Set with unique phone-numbers. Means: Some phone-numbers might be included multiple times.

My solution:

require "set"
def generate_unique_phone_numbers(path)
 numbs = Set.new
 if File.exist?(path)
 lines = File.readlines(path)
 lines.each do |line|
 numbs.add line.chomp.split(",").last
 end
 else
 puts "File does not exist."
 end
 numbs
end

Are there any improvements concerning my solution, which should be implemented?

Would you have done it completely differently? Then how and why?

• radarbob: I don't understand "Some phone-numbers might be included multiple times". This directly contradicts "return a Set with unique phone-numbers"

Answer 1

This is how I'd do it:

require "set"
require "csv"
def csv_to_iterator(path)
 CSV.open(path).collect { |(_name, number)| number } 
rescue Errno::ENOENT
 []
end
def unique(iterator)
 iterator.to_set
end
def generate_unique_phone_numbers(path)
 unique(csv_to_iterator(path))
end

Ideally I would wrap it in a class, but for simplicity methods will do for this example. I'm not sure how I feel about handling exception in the first method, but I decided to include it here since you have some handling in case a file doesn't exist in your example as well.

Rationale:

1. My methods are targeting an interface instead of a concrete implementation. So for instance, it will be easier to replace csv_to_iterator to something else, let's say a DB call in case our data source changes, as long as they quack like an Enumerable.

2. The methods are congruent. In the example you might return a Set or nil (due to puts), in my case I'm always returning a set, doesn't matter what. This create a coherent interface for the execution.

3. Well defined responsibilities. In the example, a single method is managing opening a file, verifying its stats, parsing, and removing duplicates. I broke down this into multiple steps and in smaller functions.