splat 参数后的可选参数 [英] Optional argument after splat argument

问题描述

这是我的程序:

def calculate(*numbers, options = {})
  add(numbers)      if options[:add]
  subtract(numbers) if options[:add] == false
end

def add(*numbers)
  numbers.reduce(:+)
end

def subtract(*numbers)
  numbers.reduce(:-)
end

p calculate(1,2)

在第 1 行，它在抱怨

On line 1, it is complaining

tests.rb:1: 语法错误，意外的'='，期待')'
def计算(*数字，选项= {})
________________________________________________^
[0.1s 内完成，退出代码为 1]

tests.rb:1: syntax error, unexpected '=', expecting ')'
def calculate(*numbers, options = {})
________________________________________________^
[Finished in 0.1s with exit code 1]

我认为这可能是 Ruby 中默认值的问题，因为在 v1.9 之前，您需要按顺序拥有所有默认值 - 但这不应该是问题，因为我的版本是

I thought it might have been a problem with default values in Ruby, because before v1.9, you were required to have all default values in order - but this shouldn't be the issue because my version is

ruby 2.0.0p195 (2013-05-14) [i386-mingw32]

我试过把所有的空格都调换，因为 ruby​​ 在方法方面似乎特别擅长那些东西，但没有骰子.

I've tried transposing the spaces all over, because ruby seems to be particular with those things when it comes to methods, but no dice.

可能是我的 splat 变量 *numbers 吗?

Could it be my splat variable *numbers ?

推荐答案

感谢 @maerics 和 @JorgWMittag -

Thanks @maerics and @JorgWMittag -

当你有一个 splat 时，它会保留所有参数，这就是为什么它不喜欢我的第二个选项"参数.我通过将我的参数更改为 -

When you have a splat, it reserves all arguments, which is why it was not liking my second "options" argument. I fixed this issue by changing my arguments around to -

def calculate(*arguments)
  options = arguments[-1].is_a?(Hash) ? arguments.pop : {}
  options[:add] = true if options.empty?
  return add(*arguments) if options[:add]
  return subtract(*arguments) if options[:subtract]
end

这篇关于splat 参数后的可选参数的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！