Ruby-on-rails 测试空或零值字符串
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Testing for empty or nil-value string
提问by Richard Brown
I'm trying to set a variable conditionally in Ruby. I need to set it if the variable is nil or empty (0 length string). I've come up with the following:
我正在尝试在 Ruby 中有条件地设置一个变量。如果变量为 nil 或空（0 长度字符串），我需要设置它。我想出了以下几点：
variable = id if variable.nil? || (!variable.nil? && variable.empty?)
While it works, it doesn't seem very Ruby-like to me. Is the a more succinct way of expressing the above?
虽然它有效，但对我来说似乎不太像 Ruby。以上是不是更简洁的表达方式？
回答by Jon Gauthier
The second clause does not need a !variable.nil?check—if evaluation reaches that point, variable.nilis guaranteed to be false (because of short-circuiting).
第二个子句不需要!variable.nil?检查——如果评估达到那个点，variable.nil保证是假的（因为短路）。
This should be sufficient:
这应该足够了：
variable = id if variable.nil? || variable.empty?
If you're working with Ruby on Rails, Object.blank?solves this exact problem:
如果您正在使用 Ruby on Rails，Object.blank?可以解决这个确切的问题：
An object is blank if it's false, empty, or a whitespace string. For example,
""," ",nil,[], and{}are all blank.
如果对象为 false、空或空白字符串，则该对象为空。例如
""，" "，nil，[]，和{}都是空白。
回答by Adrian Teh
If you're in Rails, .blank?should be the method you are looking for:
如果你在 Rails 中，.blank?应该是你正在寻找的方法：
a = nil
b = []
c = ""
a.blank? #=> true
b.blank? #=> true
c.blank? #=> true
d = "1"
e = ["1"]
d.blank? #=> false
e.blank? #=> false
So the answer would be:
所以答案是：
variable = id if variable.blank?
回答by sawa
variable = id if variable.to_s.empty?
