Can't use indexOf in List of Map in DART

问题

I have a List of Map like this

List<Map<String, String>> data = [
  {"id":"1", "name":"Job"},
  {"id":"2", "name":"Teh"},
  {"id":"3", "name":"Maru"},
  {"id":"4", "name":"Pam"},
];

void main() {
  var index = data.indexOf({"id":"1", "name":"Job"});
  print("Index: $index");
}

Result run on DartPad was: Index: -1. How can I using indexOf for Map object in List? Thanks

回答1:

It doesn't work because the two maps aren't the same Object, to solve that, you can either use const objects or use indexWhere

With const:

// Create a const (immutable) list.
List<Map<String, String>> data = const [
  {"id":"1", "name":"Job"},
  {"id":"2", "name":"Teh"},
  {"id":"3", "name":"Maru"},
  {"id":"4", "name":"Pam"},
];

void main() {
  // Search for the map.
  var index = data.indexOf(const {"id":"1", "name":"Job"});
  print("Index: $index");
}

Using indexWhere:

List<Map<String, String>> data = const [
  {"id":"1", "name":"Job"},
  {"id":"2", "name":"Teh"},
  {"id":"3", "name":"Maru"},
  {"id":"4", "name":"Pam"},
];

void main() {
  // Index where id is 1 and name is Job.
  var index = data.indexWhere((e) => e["id"] == "1" && e["name"] == "Job");
  print("Index: $index");
}

来源：https://stackoverflow.com/questions/58956044/cant-use-indexof-in-list-of-map-in-dart