班级没有任何结果吗？

Question

我写了一堂课，试图打印结果。

当我运行此代码时，我没有收到任何错误，但没有打印任何内容。 它显示为空白。

class Employer

  attr_accessor :id, :first_name, :last_name, :date_joined, :type_of_employment, :vehicle, :location

  def initialize(id, first_name, last_name, date_joined, type_of_employment)
    @employee_id = id
    @employee_first_name = first_name
    @employee_last_name = last_name
    @employee_date_joined = date_joined
    @employee_type_of_employment = type_of_employment
    @vehicle = "Honda"
    @location = "Toronto"
  end

end

emp1obj = Employer.new(1, "John", "Smith", "January 1, 2012", "Fulltime")
puts emp1obj
emp1obj.vehicle = "Honda"
puts emp1obj.first_name
puts emp1obj.last_name
emp1obj.location= "Toronto"

有人可以帮我找到问题吗？

Answer 1

您如何运行此文件？ 它在此处打印以下输出：

Honda
#<Employer:0x00000001779c68>

请注意，这些是统一的：

puts emp1obj.first_name
puts emp1obj.last_name

您需要使用：

@first_name = first_name
@last_name = last_name

代替

@employee_first_name = first_name
@employee_last_name = last_name

在构造函数中，如果要初始化它们。

Answer 2

低于不输出任何东西，作为相应的实例的变量（ @first_name ， @last_name的那些getter方法）， :first_name ， :last_name分别没有被分配任何值。

puts emp1obj.first_name
puts emp1obj.last_name

做如下

@first_name = first_name
@last_name = last_name

根据您的代码@employee_* ，不需要。

Answer 3

当您开始了解attr_accessor功能时，这一点很重要。 这是在做什么：

class Employer

def id
  @employee_id
end

def id=(str)
  @employee_id = str
end

def initialize(id)
    @employee_id = id
end

end
emp1obj = Employer.new(1)
puts emp1obj.id

如果要使用不同的实例变量名称，则需要将它们用作方法，而不是用于setter / getter的变量。

这将为您工作：

class Employer

  attr_accessor :employee_id, :employee_first_name, :employee_last_name, :date_joined, :type_of_employment, :vehicle, :location

def initialize(id, first_name, last_name, date_joined, type_of_employment)
    @employee_id = id
    @employee_first_name = first_name
    @employee_last_name = last_name
    @employee_date_joined = date_joined
    @employee_type_of_employment = type_of_employment
end

end
emp1obj = Employer.new(1, "John", "Smith", "January 1, 2012", "Fulltime")
puts emp1obj.employee_id
puts emp1obj.employee_first_name
puts emp1obj.employee_last_name