Question

我在我的班级Dog中创建了check_dog方法，检查狗是否接种过疫苗或蠕虫病毒。

但是，我发现很难想到这个语句If the dog is only vaccinated or only wormed, the dog can only be accepted by itself.

的布尔表达式

你可以在下面看到我缩进了我需要帮助的行，因为这行导致'nil'。

class Dog
    attr_accessor :name, :age, :breed, :vaccinated, :wormed

  def initialize(name, age, breed, vaccinated, wormed)
  @name = name
  @age = age
  @breed = breed
  @vaccinated = vaccinated
  @wormed = wormed
    end

  def check_dog
    if @vaccinated && @wormed == true
    puts "#{@name} can be accepted" 
   ----> elsif @vaccinated || @wormed == true
    puts "#{@name} can only be accepted by itself"
    else
    puts "#{@name} cannot be accepted"
    end
  end

end

spot = Dog.new("Spot", 5, "Labrador", true, false)
spot.check_dog # Should return: "Spot can only be accepted by itself".

Answer 1

def check_dog
  case [@vaccinated, @wormed]
  when [true, true] then "#{@name} can be accepted" 
  when [false, false] then "#{@name} cannot be accepted"
  else "#{@name} can only be accepted by itself"
  end.tap(&method(:puts))
end

这样打印并返回result。

Answer 2

你写它的方式看起来不正确...使用你的风格应该看起来像这样：

def check_dog
  if @vaccinated == true && @wormed == true
    puts "#{@name} can be accepted" 
  elsif @vaccinated == true || @wormed == true
    puts "#{@name} can only be accepted by itself"
  else
    puts "#{@name} cannot be accepted"
  end
end

为了更简单，你可以这样做

def check_dog
  if @vaccinated && @wormed # both are truthy
    puts "#{@name} can be accepted" 
  elsif @vaccinated || @wormed # one or the other are truthy
    puts "#{@name} can only be accepted by itself"
  else # falsey
    puts "#{@name} cannot be accepted"
  end
end

另请注意，该方法实际上是返回nil ..您没有返回任何内容，而是输出到stdout ...尝试将代码更改为：

def check_dog
  if @vaccinated && @wormed # both are truthy
    "#{@name} can be accepted" 
  elsif @vaccinated || @wormed # one or the other are truthy
    "#{@name} can only be accepted by itself"
  else # falsey
    "#{@name} cannot be accepted"
  end
end

如果一个或另一个是真正的布尔值

2 个答案: