leap.rb找不到模誤差

Question

想知道是否有人可以看到爲什麼我不能調用.modulo。我覺得就像我必須在課堂上稱Math一樣，但我不確定這是什麼情況。

的git：https://github.com/jbasalone/ja/tree/master/ruby/exercism.io/leap

錯誤：

test_leap_year(YearTest): 
    NoMethodError: undefined method `modulo' for nil:NilClass 
    /Users/jennyb/ja/ja/ruby/exercism.io/leap/year.rb:26:in `divbyfour?' 
    /Users/jennyb/ja/ja/ruby/exercism.io/leap/year.rb:17:in `leap?' 
    leap_test.rb:6:in `test_leap_year' 

這是我的代碼：

class Year 

    def initialize(theyear) 
     @theyear = theyear 
    end 
class << self 

    attr_reader :theyear 

    def initialize(theyear) 
     @theyear = theyear 
    end 

    def leap?(theyear) 
     divbyfour? && !acentury? || bcentury? 
    end 
    #private 

    def acentury? 
     theyear.modulo 100 == 0 
    end 

    def divbyfour? 
     theyear.modulo 4 == 0 
    end 

    def bcentury? 
     theyear.modulo 400 == 0 
    end 
    end 
    end 

這是我對它運行測試：

require 'minitest/autorun' 
require_relative 'year' 

class YearTest < MiniTest::Unit::TestCase 
    def test_leap_year 
    assert Year.leap?(1996) 
    end 

    def test_non_leap_year 
    skip 
    refute Year.leap?(1997) 
    end 

    def test_non_leap_even_year 
    skip 
    refute Year.leap?(1998) 
    end 

    def test_century 
    skip 
    refute Year.leap?(1900) 
    end 

    def test_fourth_century 
    skip 
    assert Year.leap?(2400) 
    end 
end 

Answer 1

這個工作對我來說：

class Year 

    attr_accessor :theyear 

    def initialize(theyear) 
     @theyear = theyear 
    end 

    def leap? 
     divbyfour? && !acentury? || bcentury? 
    end 
    #private 

    def acentury? 
     theyear.modulo(100) == 0 
    end 

    def divbyfour? 
     theyear.modulo(4) == 0 
    end 

    def bcentury? 
     theyear.modulo(400) == 0 
    end 
end 

然後調用它：

y = Year.new(1995) 
y.leap? 

或者您可以使用它像這樣：

class Year 

    def self.leap?(year) 
     @theyear = year 
     divbyfour? && !acentury? || bcentury? 
    end 

    def self.theyear 
     @theyear 
    end 
    #private 

    def self.acentury? 
     theyear.modulo(100) == 0 
    end 

    def self.divbyfour? 
     theyear.modulo(4) == 0 
    end 

    def self.bcentury? 
     theyear.modulo(400) == 0 
    end 
end 

然後你不」不需要初始化年級。

Year.leap?(1995) 
=> false 

Answer 2

在divbyfour方法你叫modulotheyear變量不存在。

這是修復您的問題的代碼。

class Year 
    attr_reader :theyear 

    def initialize(theyear) 
    @theyear = theyear 
    end 

    def leap? 
    divbyfour? && !acentury? || bcentury? 
    end 

    def acentury? 
    theyear.modulo(100) == 0 
    end 

    def divbyfour? 
    theyear.modulo(4) == 0 
    end 

    def bcentury? 
    theyear.modulo(400) == 0 
    end 
end 

例子：

>> year = Year.new 2014 
=> #<Year:0xb8eb15b4 @theyear=2014> 
>> year.leap? 
=> false 

我做了什麼：

• 刪除include Math。 Math doesn't implement modulo method，所以這裏不需要，無論如何你都不需要它 - Fixnumimplements its own modulo method。
• 刪除class << self一行。 Read up它做什麼。另外，initialize應該是一個實例方法，而不是一個類。這裏有一篇關於differences between instance and class methods in Ruby的好帖子。
• 在致電modulo時添加了括號。 theyear.modulo 100 == 0相當於theyear.modulo(100 == 0)，你真正想要的是theyear.modulo(100) == 0。

如果您有時間，請查看Ruby Koans - 這是學習Ruby及其習語的好方法。