my_to_i

README.md

String#my_to_i

Description

Custom implementation of String's to_i method

Usage

require_relative 'string'

"123".my_to_i # 123
"123a45".my_to_i # 123
"123.123".my_to_i # 123
"aaaaa".my_to_i # 0
"-123".my_to_i # -123

Testing

rspec string_spec.rb

string.rb

class String
  INT_LOOKUP = { "1" => 1, "2" => 2, "3" => 3, "4" => 4, "5" => 5, "6" => 6, "7" => 7, "8" => 8, "9" => 9, "0" => 0, "-" => -1 }

  def clean_i
    integer = self.split('.')[0]
    to_convert = []
    integer.split('').each do |i|
      break if INT_LOOKUP[i].nil?
      to_convert << INT_LOOKUP[i]
    end
    to_convert
  end

  def my_to_i
    clean_i.reverse.each_with_index.reduce(0) do |acc, (int, index)|
      if int == -1
        acc * -1
      else
        tens = 1
        index.times { |_|
          tens = tens * 10
        }
        acc + ( int * tens )
      end
    end
  end
end

string_spec.rb

require 'rspec'
require_relative 'string'

RSpec.describe String do
  context 'converts string of positive number to int' do
    it 'without special characters' do
      expect("123".my_to_i).to eq("123".to_i)
    end

    it 'with alphabet characters' do
      expect("123a".my_to_i).to eq("123a".to_i)
      expect("123a45".my_to_i).to eq("123a45".to_i)
    end

    it 'with decimal' do
      expect("123.123".my_to_i).to eq("123.123".to_i)
    end

    it 'with only letters' do
      expect("aaaaa".my_to_i).to eq("aaaaa".to_i)
    end
  end
  context 'converts string of negative number to int' do
    it 'without special characters' do
      expect("-123".my_to_i).to eq("-123".to_i)
    end

    it 'with alphabet characters' do
      expect("-123a".my_to_i).to eq("-123a".to_i)
      expect("-123a45".my_to_i).to eq("-123a45".to_i)
    end

    it 'with decimal' do
      expect("-123.123".my_to_i).to eq("-123.123".to_i)
    end

    it 'with only letters' do
      expect("-aaaaa".my_to_i).to eq("-aaaaa".to_i)
    end
  end
end