Scala/Java template list iteration and concatenation of string

Question

I want to iterate over a list of strings, concatenate them with the suffix/prefix "" and if it's not the last entry of the list append a comma at end.

Wanted Output example: "circle","cube","banana"

My first try is the following snippet:

@listStringifier(list: List[String]) = @{
  if (list != null && !list.isEmpty) {
   for ((string, index) <- list.zipWithIndex){if(index != list.size-1){"string",}
   else{"string"}
   }
  }
}

But this function is always empty when I use @listStringifier anywhere.

Logging within the @listStringifier block shows that it is iterating, but not assigning anything.

If I call the for loop directly in the template like this following snippet it works:

@if (list != null && !list.isEmpty) {
  for ((string, index) <- list.zipWithIndex){if(index != list.size-1){"@string",}
  else{"@string"}
  }
}

But I dont want to iterate several times so I want to assign the concatenated string to a variable afterwards.

Any help would be appreciated, thanks in advance

Thilo · Accepted Answer · 2016-09-14T08:20:56.040

3

I think mkString can do what you want

list.mkString( "'" , "','" , "'" )

edited Sep 14 '16 at 08:20

answered Sep 14 '16 at 08:00

Thilo

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Thanks for mentioning, that was exactly what I'm looking for so I replaced the single quotation mark with the double quotation marks and it worked like a charm. Like this: `list.mkString( "\"" , "\",\"" , "\"" )` Thank you for your help – Yeti Sep 14 '16 at 08:36
Yeah, I put single quotes to not go crazy on the escape sequences (is there a way in Scala to have alternative String delimiters like Perl's `q{","}`?) – Thilo Sep 14 '16 at 08:37
I don't know mate, sorry – Yeti Sep 14 '16 at 08:43

Nagarjuna Pamu · Answer 2 · 2016-09-14T09:30:20.217

1

mkString can do this elegantly

@listStringifier(list: List[String]) = @{ list mkString("", ",", "") }

if you want quotes around the strings you could do

list.map(str => s""""$str"""").mkString(",")

edited Sep 14 '16 at 09:30

answered Sep 14 '16 at 08:04

Nagarjuna Pamu

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`(""""""", """" ,"""", """"""")` was requested. – som-snytt Sep 14 '16 at 08:08
thanks for mentioning, I tried this before, but that would only append the quotes to the very first and last sign unfortunately. – Yeti Sep 14 '16 at 08:13
@Yeti: You can add the quotes to the separating comma as well to work around that. – Thilo Sep 14 '16 at 08:25
@Thilo as mentioned in your answer it works now, thank you all for your help. I cannot mark both answers as correct, indeed they are from the point of syntax – Yeti Sep 14 '16 at 08:37

Scala/Java template list iteration and concatenation of string

2 Answers2