如何从右侧分割字符串

Question

How can I split a string from right side by ',' ? From this string:

str_a = "#37/1, New Ray Street, 24th mains,2nd cross, Bangalore Karnataka India"

I want an output:

"#37/1, New Ray Street, 24th mains,2nd cross"

Answer 1

Use String#rpartition :

str_a = "#37/1, New Ray Street, 24th mains,2nd cross, Bangalore Karnataka India"
str_a.rpartition(',')
# => ["#37/1, New Ray Street, 24th mains,2nd cross", ",", " Bangalore Karnataka India"]
str_a.rpartition(',')[0]
# => "#37/1, New Ray Street, 24th mains,2nd cross"

UPDATE

If str_a does not contain , , the above code will return the empty string. Use following code if that could be an issue.

str_a = "#37/1"
head, sep, tail = str_a.rpartition(',') # => ["", "", "#37/1"]
sep == '' ? tail : head # OR   sep[0] ? head : tail
# => "#37/1"

Answer 2

While @falsetru suggestion is fairly the best if you know what the input string format is, it will return empty string if there were no commas in the input at all. Simple regexp

str_a.gsub /,[^,]*$/, ''

will return the input string intouch in such a case. Plus you have an ability to modify your input inplace with gsub! .