How to truncate a string in elixir?

Question

I'm working with slugs for elixir, the idea is: I have a string with [a-zA-Z0-9] words separated by hyphens. Like:

string = "another-long-string-to-be-truncated-and-much-text-here"

I want to be ensure that max string length equals to 30, but I also want to be sure that words aren't cut by half on reaching maximum length. So that first 30 symbols of string are another-long-string-to-be-trun but I want to have another-long-string-to-be with word truncated to be removed completely. How can I do that?

Answer 1

UPD 12/2018 Yuri Golobokov posted the better solution here, I’d suggest to use it instead of the below.

---

The simplest approach would be:

"another-long-string-to-be-truncated-and-much-text-here"
|> String.slice(0..29) 
|> String.replace(~r{-[^-]*$}, "")
#⇒ "another-long-string-to-be"

There is one glitch with it: if the hyphen is exactly on position 31, the last term will be removed. To avoid this, one might explicitly check fot the condition above:

str = "another-long-string-to-be-truncated-and-much-text-here"
case str |> String.at(30) do                                      
  "-" -> str |> String.slice(0..29)                                  
  _   -> str |> String.slice(0..29) |> String.replace(~r{-[^-]*$}, "")
end                                                               
#⇒ "another-long-string-to-be"

or:

orig = "another-long-string-to-be-cool-cated-and-much-text-here"
str = orig |> String.slice(0..29) 
unless String.at(orig, 30) == "-", do: str = str |> String.replace(~r{-[^-]*$}, "")
str
#⇒ "another-long-string-to-be-cool"