Flutter - Map not working when addAll function call

Question

This the code I have right now (I'm using Mobx):

@observable
ObservableMap dates = ObservableMap();

@action
void getDate() {
  final Map obj = {};
  final map = item['dates'].map((date) {
    DateTime key = DateTime.parse(date['date']);

    obj.addAll({
      key: ['list']
    });
  });

//    print(map);
  dates.addAll(obj);
}

I have function to call query and call getDate function.

At my UI I just call the dates but it won't return any value. The value only return if the print syntax not comment.

Any solutionn?

Solution

You are using the map method to do something for each element of item['dates']. That doesn't work because the map operation is lazy and doesn't do anything until you start using the result. You can call .toList() on the result to make it do all the computations, but that's a roundabout way to do it.

Use forEach instead to eagerly do something for each element, or, even better, use a for-in loop:

item['dates'].forEach((date) { ... });

or

for (var date in item['dates']) {
  var key = DateTime.parse(date['date']);
  obj.addAll({key: ['list']});
  // or just:
  // obj[key] = ['list'];
}

Comments

[ssuhat]

thank you. just learn something new. Map is lazy. I thought for statement will reduce performance.