Dart: Calculate all occurrences of a substring

I recently wanted to calculate all occurrences of a substring in a string with Dart. The code I used is nearly the same as you would use in Java to do this. So here’s my snippet for Dart:

int countOccurences(mainString, search) {
 int lInx = 0;
 int count =0;
 while(lInx != -1){
 lInx = mainString.indexOf(search,lInx);
 if( lInx != -1){
 count++;
 lInx+=search.length;
 }
 }
 return count;
}

You can now simply call it like that:

int countAll = countOccurences(sameRandomString, "smile");