问题描述
我只是在学习RoR所以请耐心等待。我试图用字符串写一个if或语句。这是我的代码：
I am just learning RoR so please bear with me. I am trying to write an if or statement with strings. Here is my code:
<% if controller_name != "sessions" or controller_name != "registrations" %>
我尝试了很多其他方法，使用括号和 || 但似乎没有任何效果。也许是因为我的JS背景...
I have tried many other ways, using parentheses and || but nothing seems to work. Maybe its because of my JS background...
我如何测试变量是否不等于字符串1或字符串2？
How can I test if a variable is not equal to string one or string two?
推荐答案
这是一个基本的逻辑问题：
This is a basic logic problem:
(a !=b) || (a != c)
只要b！= c，
总是为真。一旦你记住在布尔逻辑中
will always be true as long as b != c. Once you remember that in boolean logic
(x || y) == !(!x && !y)
然后你可以找到摆脱黑暗的道路。
then you can find your way out of the darkness.
(a !=b) || (a != c)
!(!(a!=b) && !(a!=c)) # Convert the || to && using the identity explained above
!(!!(a==b) && !!(a==c)) # Convert (x != y) to !(x == y)
!((a==b) && (a==c)) # Remove the double negations
（a == b）&&的唯一方法（a == c）为真是b == c。因此，既然你已经给出了b！= c，那么 if 语句将始终为false。
The only way for (a==b) && (a==c) to be true is for b==c. So since you have given b != c, the if statement will always be false.
只是猜测，但可能你想要
Just guessing, but probably you want
<% if controller_name != "sessions" and controller_name != "registrations" %>
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