Question

The following code:

str = "1, hello,2"
puts str
arr = str.split(",")
puts arr.inspect
arr.collect { |x| x.strip! }
puts arr.inspect

produces the following result:

1, hello,2
["1", " hello", "2"]
["1", "hello", "2"]

This is as expected. The following code:

str = "1, hello,2"
puts str
arr = (str.split(",")).collect { |x| x.strip! }
puts arr.inspect

Does however produce the following output:

1, hello,2
[nil, "hello", nil]

Why do I get these “nil”? Why can’t I do the .collect immediately on the splitted-array?

Thanks for the help!

Answer 1

The #collect method will return an array of the values returned by each block’s call. In your first example, you’re modifying the actual array contents with #strip! and use those, while you neglect the return value of #collect.

In the second case, you use the #collect result. Your problem is that #strip! will either return a string or nil, depending on its result – especially, it’ll return nil if the string wasn’t modified.

Therefore, use #strip (without the exclamation mark):

1.9.3-p194 :005 > (str.split(",")).collect { |x| x.strip }
 => ["1", "hello", "2"]