Question

我试图为我的应用程序实现一个元素，但无法解决如何减少if语句的数量问题。我实现了以下工作，但if语句的数量是荒谬的。更不用说我必须为＆＃34; x＆＃34;。

以外的变量重复相同的代码

if x.color includes "red"
     print "red"
elsif x.color includes "blue"
     print "blue"
elsif x.color includes "yellow"
     print "yellow"
elsif x.color includes "red" and "blue"
     print "red and blue"
...

...
elsif x.color includes "red" and "blue" and "yellow"
     print "red and blue and yellow"
else
     print "none"
end

有没有办法用较少的代码来解释所有条件？

非常感谢你的时间！

Answer 1

colors =  %w[red blue yellow].select { |color| x.color.include?(color) }
print colors.count.zero? ? 'none' : colors.join(' and ')

Answer 2

如果您希望x.colors中的颜色多于红色和黄色。你可以先做＆amp;使用此数组输入，然后使用和。

连接它

common_colors = x.colors & %w(red blue yellow)
unless common_colors.empty? 
  puts colors.join(" and ")
else
  puts "none"
end

此外，您无需重复所有颜色即可。您可以对它们使用迭代。假设您有3个变量x，y和z。

[x, y, z].each do |var|
  common_colors = var.colors & %w(red blue yellow)
  unless common_colors.empty? 
    puts colors.join(" and ")
  else
    puts "none"
  end
end

Answer 3

我的2美分是，每当在Ruby中编写任何可重用的东西时，你都应该采用OOP方式。在您的情况下，可能的解决方案之一是：

class X
  class Color < String
    VALID = "red", "blue", "yellow"

    def self.new color
      fail TypeError, "Invalid color: #{color}!" unless VALID.include? color
      super
    end
  end

  attr_reader :color

  def initialize *colors
    @color = colors.map { |c| Color.new c }.uniq.sort # Turn them into Color objects.
  end

  def present_yourself
    puts "I'm #{color_string}."
  end

  private

  # This method is the remnant of your if statements. I made it private just to demonstrate
  # that you can (and should) hide the engines from the object user.
  #
  def color_string
    return "colorless" if color.empty?        # No color case.
    return color[0] if color.size == 1        # Single color case.
    # Two or more colors case:
    color.tap { |*colors, color| return colors.join( ", " ) + " and " + color }
  end
end

这个小基础设施很容易重构，让你可以做你想做的事情，而不必关心它是如何完成的：

x = X.new
x.present_yourself
#=> I'm colorless.

x = X.new "red", "blue", "yellow"
x.present_yourself
#=> I'm blue, red and yellow.

x = X.new "red", "blue", "foobar"
#=> TypeError: Invalid color: foobar!

减少if语句的数量

3 个答案: