class argument/variable 后续参数中的范围应用程序/参数结果引用

Question

我的任务是用 class 个参数制作一个利息计算器，但我很难应用 variables/arguments。我一直收到参数错误（4 为 0）。此外，如何在我的“陈述”论证中正确引用 amount 论证结果？有什么建议么？任何人都可以提供见解以帮助我在这种情况下更好地理解范围界定吗？

class InterestCalculator
  attr_accessor :principal, :rate, :years, :times_compounded

  def intitialize(principal, rate, years, times_compounded)
    @principal, @rate, @years, @times_compounded = principal, rate, years, times_compounded
  end

  def amount
    amount = @principal * (1 + @rate / @times_compounded) ** (@times_compounded * @years)
  end  

  def statement
    "After #{@years} I'll have #{amount} dollars!"
  end
end

这些是规格：

describe InterestCalculator do

  before { @calc = InterestCalculator.new(500, 0.05, 4, 5) }

  describe "#amount" do
    it "calculates correctly" do
      expect( @calc.amount ).to eq(610.1)
    end
  end

  describe "#statement" do
    it "calls amount" do
      @calc.stub(:amount).and_return(100)
      expect( @calc.statement ).to eq("After 4 years I'll have 100 dollars!")
    end
  end
end

Answer 1

您输入了 initialize 方法 ("intitialize")，因此 ruby 认为您仍在使用不带参数的默认初始化方法，因此出现错误。

Answer 2

Frederick Cheung 是正确的，但他们也在寻找要四舍五入的数字 "eq(610.1)"

def amount
    amount = @principal * (1 + @rate / @times_compounded) ** (@times_compounded * @years)
  end

应该是...

def amount
    amount = @principal * (1 + @rate / @times_compounded) ** (@times_compounded * @years)
    amount.round(2)
  end

class argument/variable 后续参数中的范围应用程序/参数结果引用

class argument/variable scope application / argument result references in subsequent argument

ruby

scope

class