Bang! methods

Kasia Ekiert — Sat, 28 Oct 2023 14:56:23 +0000

Ruby Bang methods (!) are a naming convention that indicates that a method can be "dangerous" or modify its receiver. For example, downcase! changes the original string to lowercase, while downcase returns a new string. Bang methods are not always destructive, but they usually want to get your attention.
The merge! method is a way to combine two hashes into one, by adding the contents of the second hash to the first one. If the hashes have duplicate keys, the values from the second hash will overwrite the values from the first one.

Ruby on Rails Bang methods (!) are methods that raise an exception when something goes wrong, such as finding a record in the database or saving a model.

Metody Bang w Ruby i w Ruby on Rails to metody, które używamy z wykrzyknikiem.
Co osiągamy poprzez użycie ! ?

Zapisujemy zamiane na obiekcie.
Użycie metody merge! na hashach powoduje powstanie nowego hasha - z dwóch podanych. Jeśli w drugim hashu będą zduplikowane klucze - z pierwszego hasha - zostaną nadpisane (chyba, że zostanie to wcześniej rozwiązane inaczej ;)
W Ruby on Rails użycie ! dodatkowo - sprawdza walidacjami czy dany obiekt może powstać i zwraca nam ewentualne errory.

Usage of method reduce in Ruby

Kasia Ekiert — Wed, 25 Oct 2023 08:35:43 +0000

Usage of reduce in ruby and a task:
Write a program that displays the sum of predecessors for the next 10 natural numbers. Expected result: 1, 3, 6, 10, 15, 21, 28, 36, 45, 55.

My solution:

def counter(n)
  sum = 0 
  letters = []
  (1..n).each do |number|
    sum += number
    letters << sum
  end
  letters.join(", "). #remember to create an array first and then to join letters inside
end 

puts counter(10) #result: 1, 3, 6, 10, 15, 21, 28, 36, 45, 55

Tests:

require './training1'

RSpec.describe '#counter' do
  subject { counter(n) }

  context 'It gives partial sums of the numbers' do
    let(:n) { 10 }

    it "should return a line of numbers" do
      expect(subject).to eq("1, 3, 6, 10, 15, 21, 28, 36, 45, 55")
    end
  end
end

But if we don’t need to display all numbers and we need just a sum of them, we may use the method reduce:


def counter(n)
  (1..n).reduce(:+) 
end 

puts counter(10) #result: 55

https://apidock.com/ruby/Enumerable/reduce

Enjoy :)

DEV Community: Kasia Ekiert

Bang! methods

Usage of method reduce in Ruby