leap.rb找不到模误差
leap.rb找不到模误差
提问于 2014-03-30 22:42:06
想知道为什么我不能打电话给.modulo。我觉得好像我必须在课堂上给数学打电话，但我不确定是这样的。
git：https://github.com/jbasalone/ja/tree/master/ruby/exercism.io/leap
错误：
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'这是我的密码：
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这就是我所面临的考验：
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回答 2
Stack Overflow用户
回答已采纳
发布于 2014-03-30 23:04:27
这对我来说很管用：
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然后你用：
y = Year.new(1995)
y.leap?或者，您可以像这样使用它：
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然后就不需要初始化you类了。
Year.leap?(1995)
=> falseStack Overflow用户
发布于 2014-03-30 23:01:08
在divbyfour方法中，对不存在的theyear变量调用modulo。
这里有一个代码可以解决你的问题。
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示例：
>> year = Year.new 2014
=> #<Year:0xb8eb15b4 @theyear=2014>
>> year.leap?
=> false我所做的：
- 移除
include Math。方法，所以这里不需要它，反正你也不需要它--Fixnum方法。 - 移除
class << self线。读完关于它所做的事情。而且，initialize应该是一个实例方法，而不是类方法。这是Ruby中实例方法和类方法的区别上的一个很好的帖子。 - 在对
modulo的调用中添加括号。theyear.modulo 100 == 0相当于theyear.modulo(100 == 0)，您真正想要的是theyear.modulo(100) == 0。
如果您有时间，请查看红宝石考恩 --这是学习Ruby及其成语的一个很好的方法。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/22750873
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