如何在ruby中声明模块中的函数

在下面的代码中，以不同的方式声明两个方法有什么区别。第二种方法是使用

Week

声明的，但第一种方法是在不使用

Week

的情况下声明的。我们也无法通过类对象

d1

访问第二个方法。它给出了错误

undefined method `weeks_in_year' for #<Decade:0x2c08a28> (NoMethodError)

---

您定义方法

weeks\u in_year

的方式是

Week

类的类方法，而不是实例方法。这就是为什么它没有被继承，而您在发布时得到了错误

可以使用来使用与类方法或实例方法相同的方法

module Week
  def weeks_in_month
    puts "You have four weeks in a month"
  end

  def weeks_in_year
    puts "You have 52 weeks in a year"
  end

  module_function :weeks_in_year
end

class Decade
  include Week

  def wrapper_of_weeks_in_year
    weeks_in_year
  end
end

d1 = Decade.new

d1.weeks_in_month
# You have four weeks in a month
d1.wrapper_of_weeks_in_year
# You have 52 weeks in a year
Week.weeks_in_year
# You have 52 weeks in a year

当您将使用

模块_函数

时，实例方法版本是私有的。这就是为什么您需要使用包装器方法来调用它，因为直接调用是不可能的

module Week
  def weeks_in_month
    puts "You have four weeks in a month"
  end

  def weeks_in_year
    puts "You have 52 weeks in a year"
  end

  module_function :weeks_in_year
end

class Decade
  include Week

  def wrapper_of_weeks_in_year
    weeks_in_year
  end
end

d1 = Decade.new

d1.weeks_in_month
# You have four weeks in a month
d1.wrapper_of_weeks_in_year
# You have 52 weeks in a year
Week.weeks_in_year
# You have 52 weeks in a year