Extracting a Word after delimiter in scala - scala

Question

I want to extract a word from a String in Scala
val text = "This ball is from Rock. He is good boy"
I want to extract "Rock" from the string.
I tried:
val op = text.subString(4)
text is not a fixed length string. I just want to pick first word after "From".
This doesnt give the right word. can anyone suggest.

Answer 1

This does what you want:
text.drop(text.indexOfSlice("from ")+5).takeWhile(_.isLetter)
or more generally
val delim = "from "
text.drop(text.indexOfSlice(delim)+delim.length).takeWhile(_.isLetter)
The indexOfSlice finds the position of the delimiter and the drop removes everything up to the end of the delimiter. The takeWhile takes all the letters for the word and stops at the first non-letter character (in this case ".").
Note that this is case sensitive so it will not find "From ", it will only work with "from ". If more complex testing is required then use split to convert to separate words and check each word in turn.

Answer 2

This is because you are telling scala to print everything from 4th index to end of string.
In your case you first want to split the string into words which can be done using split function and then access the word you want.
Note: split gives you an array of string and array index begin from 0 in scala so rock would be at the 4th index
This piece of code should work for you. Basically I am using a function to the processing of index of the word that immediately follows a substring (in this case from)
val text = "This ball is from Rock. He is good boy"
val splitText = text.split("\\W+")
println(splitText(4))
Based on your comment below, I would create a code something like this
import scala.util.control.Breaks.{break, breakable}
object Question extends App {
val text = "This ball is from Rock. He is from good boy"
val splitText = text.split("\\W+")
val index = getIndex(splitText, "from")
println(index)
if (index != -1) {
println(splitText(index))
}
def getIndex(arrSplit: Array[String], subString: String): Int = {
var output = -1
var index = 0
breakable {
for(item <- arrSplit) {
if(item.equalsIgnoreCase(subString)) {
output = index + 1
break
}
index = index + 1
}
}
output
}
}

Answer 3

I hope this is what you are expecting:
object Test2 extends App {
val text = "This ball is from Rock. He is good boy"
private val words = text.split(" ")
private val wordToTrack = "from"
val indexOfFrom = words.indexOf(wordToTrack);
val expectedText = words.filterNot{
case word if indexOfFrom < words.size & words.contains(wordToTrack) =>
word == words(indexOfFrom + 1)
case _ => false
}.mkString(" ")
print(expectedText)
}
words.contains(wordToTrack) guards the scenario if the from word(i.e tracking word for this example) is missing in the input text string.
I have used the partial function along with the filter to get the desired result.

Answer 4

You probably want something more general so that you can extract a word from a sentence if that word is present in the input, without having to hard-code offsets:
def extractWordFromString(input: String, word: String): Option[String] = {
val wordLength = word.length
val start = input.indexOfSlice(word)
if (start == -1) None else Some(input.slice(start, start + wordLength))
}
Executing extractWordFromString(text, "Rock") will give you an option containing the target word from input if it was found, and an empty option otherwise. That way you can handle the case where the word you were searching for was not found.