Getting stackoverflow on recursion - dart

Question

I want to generate INSERT statement from JSON. The problem that I have problem with recursion (in section where I am getting nested elements). it's seems that I am getting SO.
import 'dart:convert';
main() {
Map jsonMap = jsonDecode(
'{"id":"1","name":"sample","Lots":[{"id":"1","title":"books","objs":[{"book":"name"}]}]}');
KVToTableInsert(String tablename, Map jsonMap) {
List<String> insertNoticeKeys = [];
List<String> insertNoticeValues = [];
jsonMap.forEach((key, value) {
if (value is List) // nested
{
KVToTableInsert(key, jsonMap); // if comment this line all work
} else {
insertNoticeKeys.add(key);
insertNoticeValues.add(value);
}
});
String sql = "INSERT INTO $tablename (" +
insertNoticeKeys.map((e) => '"$e"').join(', ') +
") VALUES (" +
insertNoticeValues.map((e) => "'$e'").join(', ') +
")";
print(sql);
}
KVToTableInsert("RootTable", jsonMap);
}
I expected to get 3 INSERT statment:
INSERT INTO RootTable ("id", "name") VALUES ('1', 'sample')
INSERT INTO Lots ("id", "title") VALUES ('1', 'books')
INSERT INTO Objs ("book") VALUES ('name')
But I am getting crush on this app.

Answer 1

There was a slight problem in your code, basically in this part:
if (value is List){
KVToTableInsert(key, jsonMap); // if comment this line all work
}
If you closely, take a look at your KVToTableInsert, you're passing arguments Map and not list. Which fails your recursion.
What you need to do is to pass the item of the array, into your KVToTableInsert, and this will work as expected
FINAL SOLUTION
// taking your jsonMap directly, and not decoding it
void main() {
Map jsonMap = {
"id":"1",
"name":"sample",
"Lots":[
{
"id": "1",
"title":"books",
"objs":[
{
"book":"name"
}
]
}
]
};
void KVToTableInsert(tablename, jsonMap){
List<String> insertNoticeKeys = [];
List<String> insertNoticeValues = [];
jsonMap.forEach((key,value){
if (value is List)
{
// Here is the magic, you need to iterate over your list, and pass MAP, not LIST
value.forEach((item){ KVToTableInsert(key, item);});
} else {
insertNoticeKeys.add(key);
insertNoticeValues.add(value);
}
});
String sql = "INSERT INTO $tablename (" +
insertNoticeKeys.map((e) => '"$e"').join(', ') +
") VALUES (" +
insertNoticeValues.map((e) => "'$e'").join(', ') +
")";
print(sql);
}
KVToTableInsert("Rootable", jsonMap);
}
OUTPUT
INSERT INTO objs ("book") VALUES ('name')
INSERT INTO Lots ("id", "title") VALUES ('1', 'books')
INSERT INTO Rootable ("id", "name") VALUES ('1', 'sample')
Also, look at the Dart Programming Language Naming Conventions, it is a good practise to use lowerCamelCase for your function/method name.