Ruby Koan 151提出异常

Question

我正在经历红宝石公案,我在151岁,我只是碰到了一堵砖墙.

这是公案:

# You need to write the triangle method in the file 'triangle.rb'
require 'triangle.rb'

class AboutTriangleProject2 < EdgeCase::Koan
  # The first assignment did not talk about how to handle errors.
  # Let's handle that part now.
  def test_illegal_triangles_throw_exceptions
    assert_raise(TriangleError) do triangle(0, 0, 0) end
    assert_raise(TriangleError) do triangle(3, 4, -5) end
    assert_raise(TriangleError) do triangle(1, 1, 3) end
    assert_raise(TriangleError) do triangle(2, 4, 2) end
 end
end

然后在triangle.rb中我们有:

def triangle(a, b, c)
  # WRITE THIS CODE
  if a==b && a==c
    return :equilateral
  end
  if (a==b && a!=c) || (a==c && a!=b) || (b==c && b!=a)
    return :isosceles
  end
  if a!=b && a!=c && b!=c
    return :scalene
  end
  if a==0 && b==0 && c==0
    raise new.TriangleError
  end



end

# Error class used in part 2.  No need to change this code.
class TriangleError < StandardError

end

我很困惑 - 任何帮助都会非常感激!

编辑:要完成这个公案,我需要在TriangleError类中添加一些内容 - 但我不知道是什么

更新:这是koan业力的事情:

<TriangleError> exception expected but none was thrown.

Answer 1

1. 三角形不应具有长度为0的任何边.如果是,则它可以是线段或点,具体取决于边数是多少.
2. 负长度没有意义.
3. 三角形的任何两边应该加起来超过第三边.
4. 见3,重点是"更多".

您不需要更改TriangleError代码AFAICS.看起来你的语法有点古怪.尝试改变

raise new.TriangleError

至

raise TriangleError, "why the exception happened"

此外,您应该在对它们执行任何操作之前测试值(并抛出异常).将异常内容移动到函数的开头.

Answer 2

当a,b或c为负时,你忘记了这种情况:

def triangle(a, b, c)
  raise TriangleError if [a,b,c].min <= 0
  x, y, z = [a,b,c].sort
  raise TriangleError if x + y <= z
  [:equilateral,:isosceles,:scalene].fetch([a,b,c].uniq.size - 1)
end

Answer 3

结束这样做:

def triangle(a, b, c)
  a, b, c = [a, b, c].sort
  raise TriangleError if a <= 0 || a + b <= c
  [nil, :equilateral, :isosceles, :scalene][[a, b, c].uniq.size]
end

感谢这里的评论者:)

Answer 4

我喜欢Cory的回答.但是我想知道,如果你有两个测试,有什么理由或任何东西可以获得:

raise TriangleError, "Sides must by numbers greater than zero" if (a <= 0) || (b <= 0) || (c <= 0)
raise TriangleError, "No two sides can add to be less than or equal to the other side" if (a+b <= c) || (a+c <= b) || (b+c <= a)

Answer 5

您无需修改​​异常.这样的事情应该有效;

def triangle(*args)
  args.sort!
  raise TriangleError if args[0] + args[1] <= args[2] || args[0] <= 0
  [nil, :equilateral, :isosceles, :scalene][args.uniq.length]
end

Answer 6

def triangle(a, b, c)
  [a, b, c].permutation do |sides|
    raise TriangleError unless sides[0] + sides[1] > sides[2]
  end
  case [a,b,c].uniq.size
    when 3; :scalene
    when 2; :isosceles
    when 1; :equilateral
  end
end

Answer 7

我想要一种能够有效解析所有参数的方法，而不是依赖于测试断言中给出的顺序。

def triangle(a, b, c)
  # WRITE THIS CODE
  [a,b,c].permutation { |p| 
     if p[0] + p[1] <= p[2]
       raise TriangleError, "Two sides of a triangle must be greater than the remaining side."
     elsif p.count { |x| x <= 0} > 0
       raise TriangleError, "A triangle cannot have sides of zero or less length."
     end
  }

  if [a,b,c].uniq.count == 1
    return :equilateral
  elsif [a,b,c].uniq.count == 2
    return :isosceles
  elsif [a,b,c].uniq.count == 3
    return :scalene
  end
end

希望这可以帮助其他人认识到剥猫皮的方法不止一种。