Ruby：“如果 !object.nil？” 或“如果对象”
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Ruby: "if !object.nil?" or "if object"
提问by bigpotato
Are they the same when used in an if/else/endstatement? What do you usually do? I'm wondering if there are any subtle differences or edge cases where objectand !object.nil?would respond differently.
它们在if/else/end语句中使用时是否相同？你平常都做什么？我想知道是否有任何细微的差异或边缘情况，object并且!object.nil?会做出不同的反应。
回答by Marek Lipka
There are differences. For example:
存在差异。例如：
false.nil?
# => false
So:
所以：
if !false.nil?
'foo'
end
# => "foo"
if false
'foo'
end
# => nil
As @tokland suggested, in most cases using !obj.nil?construction is unnecessary.
正如@tokland 所建议的，在大多数情况下使用!obj.nil?构造是不必要的。
回答by Christopher Oezbek
There is one and only one case in which !object.nil?and objectevaluate to different results in a boolean context and that is if objectis false. In all other situations the result is the same.
有一种且只有一种情况，其中!object.nil?andobject在布尔上下文中评估为不同的结果，即 if objectis false。在所有其他情况下，结果都是一样的。
With this, I think we can answer your real question (which is: Is there any situation where I must use if !object.nil?instead of just if objectwhen protecting against objectbeing nil?):
有了这个，我想我们可以回答你真正的问题（即：有什么情况我必须使用if !object.nil?而不是仅仅if object在防止object为零时使用？）：
No, you can always use if objectif you want to check against nil.
不，if object如果你想检查，你可以随时使用nil。
回答by Yu Hao
回答by Anton
Well. if objectwill behave differently from if !object.nil?if object=false.
好。if object将与if !object.nil?if不同object=false。
That's about it.
就是这样。
回答by Logan Serman
Objects can override nil?but they cannot be falsely unless they are nil or false. Personally I use nil?or ActiveSupport's present?so that I maintain that flexibility. I also think it reads a bit better.
对象可以覆盖，nil?但它们不能是错误的，除非它们是 nil 或 false。我个人使用nil?ActiveSupport 或 ActiveSupport，present?以便保持这种灵活性。我也觉得读起来好一点。
