ruby - =~ 运算符的顺序重要吗？

Question

下面两个语句除了编码风格有区别吗？

/regex/=~ "some_string_with_regex"

"some_string_with_regex"=~/regex/

Answer 1

是的，有区别。正如在 http://www.ruby-doc.org/core/classes/Regexp.html#M001232 中提到的

If =~ is used with a regexp literal with named captures, captured strings (or nil) is assigned to local variables named by the capture names.

/(?<lhs>\w+)\s*=\s*(?<rhs>\w+)/ =~ "  x = y  "
p lhs    #=> "x" 
p rhs    #=> "y"

...

The assignment is not occur if the regexp is placed at right hand side.

"  x = y  " =~ /(?<lhs>\w+)\s*=\s*(?<rhs>\w+)/
p lhs, rhs # undefined local variable

String#~=