Class: CompoundInterest::Calculation

Inherits:
Object
  • Object
show all
Defined in:
lib/compound_interest/calculation.rb

Class Method Summary collapse

Class Method Details

.calculate(params) ⇒ Object 



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# File 'lib/compound_interest/calculation.rb', line 5

def self.calculate(params)
  raise_error(params)

  @initial_payment = params[:initial_payment]
  # number of terms
  @term = params[:term]
  # interest rate per term
  @interest_rate = params[:interest_rate].to_f / 100
  # number of interest payments for the term
  @capitalization_periodicity = params[:capitalization_periodicity]
  @payment = params[:payment] || 0
  # number of payments for the term
  @payment_periodicity = params[:payment_periodicity]

  result
end

.compound_interest_formula(num = 0) ⇒ Object 



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# File 'lib/compound_interest/calculation.rb', line 37

def self.compound_interest_formula(num = 0)
  if num.zero?
    (1.0 + @interest_rate / @capitalization_periodicity)**(@term * @capitalization_periodicity)
  else
    (1.0 + @interest_rate / @capitalization_periodicity)**((@term * @capitalization_periodicity) -
        (@capitalization_periodicity / @payment_periodicity * num))
  end
end

.periodical_payment_calculation ⇒ Object 



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# File 'lib/compound_interest/calculation.rb', line 28

def self.periodical_payment_calculation
  times = (@payment_periodicity * @term).to_i
  payment_result = 0
  (1..times).each do |i|
    payment_result += @payment * compound_interest_formula(i)
  end
  payment_result
end

.raise_error(params) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/compound_interest/calculation.rb', line 46

def self.raise_error(params)
  raise "Argument must be Hash" if params.class != Hash
  raise ArgumentError, "Argument must include :initial_payment" if params[:initial_payment].nil?
  raise ArgumentError, "Argument must include :term" if params[:term].nil?
  raise ArgumentError, "Argument must include :interest_rate" if params[:interest_rate].nil?
  raise ArgumentError, "Argument must include :capitalization_periodicity" if [:capitalization_periodicity].nil?
end

.result ⇒ Object 



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# File 'lib/compound_interest/calculation.rb', line 22

def self.result
  result = @initial_payment * compound_interest_formula
  result = periodical_payment_calculation if @payment.positive?
  result
end