Question

Let string_a = "I'm a very long long long string"

Is there a method in Ruby that truncates a string something like this?:

magic_method(string_a) # => "I'm a ver...ng string"

In Rails I can do: truncate(string_a) but only the first part is returned.

Answer 1

You can try the method String.scan with a regular expression to break the string where you wish. Try somenthing like:

def magic_method(string_x)
    splits = string_x.scan(/(.{0,9})(.*?)(.{0,9}$)/)[0]
    splits[1] = "..." if splits[1].length > 3
    splits.join
end

Explanation:
Supose string_a = "I'm a very long long long string"; string_b = "A small test string"; and string_c = "tiny". First split the string within 3 groups.

• The first group (.{0,9}) try to catch the first 9 or less characters. Ex. "I'm a ver" for string_a; "A small t" for string_b and "tiny" for string_c.
• The last group (.{0,9}$) try to catch the last 9 or less characters and the end of string ($). Ex."ng string" for string_a; "st string" for string_b and "" for string_c;
• The middle group (.*?) try to catch what is left over. This only works because of the ? that makes this regular expression not greedy (otherwise it would get the rest of the string, lefting nothing to the last group. Ex: "y long long lo" for string_a, "e" for string_b and "" for string_c

Than we check if the middle group is greater than 3 characters, if so, we replace with "...". This will only happen on string_a. Here we wouldn’t like to make string_b longer, replacing "e" with "..." resulting in "A simple t...st string".

Finally join the groups (array elements) into a single string with Array.join