Continuously add data to Map

Question

I need to add data to a Map or HashMap before a for...loop, add data to the Map during the for...loop and then create the document with all of the data after the loop.

Answer 1

An equivalent block of code to what you wrote in Java, for Dart, is:

Map<String, Object> createDoc = new HashMap();
createDoc['type'] = type;
createDoc['title'] = title;
for (int x = 0; x < sArray.length; x++) {
  createDoc['data' + x] = sArray[x];
}

Of course, Dart has type inference and collection literals, so we can use a more short-hand syntax for both. Let's write the exact same thing from above, but with some more Dart (2) idioms:

var createDoc = <String, Object>{};
createDoc['type'] = type;
createDoc['title'] = title;
for (var x = 0; x < sArray.length; x++) {
  createDoc['data' + x] = sArray[x];
}

OK, that's better, but still is not using everything Dart provides. We can use the map literal instead of writing two more lines of code, and we can even use string interpolation:

var createDoc = {
  'type': type,
  'title': title,
};
for (var x = 0; x < sArray.length; x++) {
  createDoc['data$x'] = sArray[x];
}

---

I also imported dart:collection to use HashMap, but it won't let me use

Map<String, Object> newMap = new HashMap<>(); I get the error: `"A value of type 'HashMap' can't be assigned to a variable of type

'Map'`"

There is no such syntax new HashMap<> in Dart. Type inference works without it, so you could just write Map<String, Object> map = new HashMap(), or like my above example, var map = <String, Object> {}, or even better, var map = { 'type': type }, which will type the map for you based on the key and value.

I hope that helps!