Flutter how to turn Lists encoded as Strings for a SQFL database back to Lists concisely? - sql

Question

I fear I'm trying to reinvent the wheel here. I'm putting Objects into my SQFL database:
https://pub.dev/packages/sqflite
some of the object fields are Lists of ints others are Lists of Strings. I'm encoding these as plain Strings to place in a TEXT field in my SQFL database.
At some point I'm going to have to turn them back, I couldn't find anything on Google, which is surprising because this must be a very common occurrence with SQFL
I've started coding the 'decoding', but it's rookie dart. Is there anything performant around I ought to use?
Code included to prove I'm not totally lazy, no need to look, edge cases make it fail.
List<int> listOfInts = new List<int>();
String testStringOfInts = "[1,2,4]";
List<String> intermediateStep2 = testStringOfInts.split(',');
int numListElements = intermediateStep2.length;
print("intermediateStep2: $intermediateStep2, numListElements: $numListElements");
for (int i = 0; i < numListElements; i++) {
if (i == 0) {
listOfInts.add(int.parse(intermediateStep2[i].substring(1)));
continue;
}
else if ((i) == (numListElements - 1)) {
print('final element: ${intermediateStep2[i]}');
listOfInts.add(int.parse(intermediateStep2[i].substring(0, intermediateStep2[i].length - 1)));
continue;
}
else listOfInts.add(int.parse(intermediateStep2[i]));
}
print('Output: $listOfInts');
/* DECODING LISTS OF STRINGS */
String testString = "['element1','element2','element23']";
List<String> intermediateStep = testString.split("'");
List<String> output = new List<String>();
for (int i = 0; i < intermediateStep.length; i++) {
if (i % 2 == 0) {
continue;
} else {
print('adding a value to output: ${intermediateStep[i]}');
//print('value is a: ${(intermediateStep[i]).runtimeType}');
output.add(intermediateStep[i]);
}
}
print('Output: $output');
}

Answer 1

For the integers your could make the parsing like:
void main() {
print(parseStringAsIntList("[1,2,4]")); // [1, 2, 4]
}
List<int> parseStringAsIntList(String stringOfInts) => stringOfInts
.substring(1, stringOfInts.length - 1)
.split(',')
.map(int.parse)
.toList();
I need more information about how the Strings are saved in some corner cases like if they contain , and/or ' since this will change how the parsing should be done. But if both characters are valid in the string (especially ,) I will recommend you to change the storage format into JSON instead which makes it a lot easier to encode/decode and without the risk of using characters which can give you issues).
But a rather naive solution can be made like this if we know each String does not contain ,:
void main() {
print(parseStringAsStringList("['element1','element2','element23']"));
// [element1, element2, element23]
}
List<String> parseStringAsStringList(String stringOfStrings) => stringOfStrings
.substring(1, stringOfStrings.length - 1)
.split(',')
.map((string) => string.substring(1, string.length - 1))
.toList();