Calculator. This method calculates the result of the basic mathematical operations in a string

string_calculator.rb

def calculator string
  while string.match /[*\/]/
    # p string
    string.gsub!(/(\d+)\s*([*\/])\s*(\d+)/) do |regex| 
      num1 = $1.to_i
      num2 = $3.to_i
      operator = $2.to_sym
      "#{[num1, num2].reduce(operator)}"
    end
  end

  while string.match /[-\+]/
    string.gsub!(/(\d+)\s*([-\+])\s*(\d+)/) do |regex| 
      num1 = $1.to_i
      num2 = $3.to_i
      operator = $2.to_sym
      "#{[num1, num2].reduce(operator)}"
    end
  end

  string.to_i
end

string_calculator_spec.rb

require 'calculator'

describe "method calculator exist" do
  it "calculator 2 + 3 == 5" do 
    expect(calculator("2 + 3")).to eq 5
  end
end

describe "method subtraction" do
  it "10 - 5 == 5" do
    expect(calculator("10 - 5")).to eq(5)
  end
end

describe "method with multiple operators" do
  it "10 - 5 == 5" do
    expect(calculator("12 + 1 * 2 + 4 / 2")).to eq(16)
  end
end