Ruby相当于JavaScript运算符`||`

Question

How can this be achieved in Ruby? Can it be done without repeating the variable? Javascript:

b = a || 7

This assigns a if a is not 0 and 7 otherwise

One specific case is converting date.wday to 7 if it returns 0 (Sunday).

Answer 1

There are only two falsy values in Ruby: nil and false . So, if you really want this approach

a = b == 0 ? 7 : b

is a plausible solution, because 0 can't be evaluated as false .

However, a better option for your need is cwday , and not wday . Then you don't need to make this comparison anymore, because it returns 1 for Monday, 2 for Tuesday, and finally 7 for Sunday, as you need.

date = Date.new(2016,19,6) # => Jun 19 2016, Sunday
date.cwday # => 7

Answer 2

Just out of curiosity:

class Object
  def javascript_or?(other)
    (is_a?(FalseClass) || nil? || '' == self || 0 == self) ? nil : self
  end
end

and:

a = b.javascript_or?(7)

Answer 3

For the particular case of 0 and 7 :

a = (b + 6) % 7 + 1

:)

Answer 4

您可以使用三元运算符：

 date.wday == 0 ? 7 : date.wday

Answer 5

What you're describing here is less of a logical problem and more of a mapping one:

WEEKDAY_MAP = Hash.new { |h,k| h[k] = k < 7 ? k : nil }.merge(0 => 7)   

This one re-writes 1..6 to be the same, but 0 becomes 7. All other values are nil .

Then you can use this to re-write your day indicies:

b = WEEKDAY_MAP[a]

If at some point you want to tinker with the logic some more, that's also possible.