My First Ruby Console App

Just started playing around with Ruby, and this is what I did after reading some tutorials.

A basic console app to demonstrate the use of ruby hash to lookup city code based on given city name.

To run the program, you've to install ruby in your computer. If you're not sure, just open your terminal\/shell\/cmd and issue this command ruby -v. If ruby is installed, the command will display version of your ruby.

Then, put below code to a file named (for example) city_code.rb and execute the file ruby /path/to/city_code.rb.

The Code

dial_book = { 
    "newyork" => "212", 
    "edison"  => "908"
}

# extract city names from hash keys
def get_city_names(hash) 
    hash.keys
end

# extract city code names from hash keys
def get_city_code(city_data, city) 
    city_data[city]
end

loop do 
    cities = get_city_names(dial_book) 
    puts "Choose city from list to lookup its code:" 
    puts cities.join "\n"

    answer = gets.chomp

    if cities.include?(answer) 
        code = get_city_code(dial_book, answer) 
        puts "\n\nThe code for #{answer} is #{code}\n\n" 
    else 
        puts "\n\nThere's no data for city '#{answer}'\n\n" 
    end
end

Screenshot

Still want more?

Let's explain what happens in the code.

The dial_book variable is a ruby hash, where we can store pairs of key & value. In ruby, the => inside hash can be referred as hash rocket.

Method in Ruby started with def methodname(param) keyword and ended with end keyword.

In above code, we defined a method called get_city_names which accepts single parameter called hash.

Unless we want to break out early, we don't need to write return keyword, Ruby returns the last evaluated expression automatically.

cities.include? – notice the question mark there.

This is a convention in ruby world. Method that returns boolean will have quesetion mark (?) at the end of its name.

When calling a method, we can omit the bracket for parameter. So, instead of writing cities.include?(answer) we can write cities.include? answer. Whichever we feel comfortable. Nice isn't it?