Flutter/Dart：如何从方法返回一个列表并将其设置为另一个列表

Question

Problem: How to retrieve from a list and append to a new list saved locally, to be used by methods in the same class.

I would like to store whats in exerciseList and put it into the local variable List CustomExercises; When I return custom exercises from getAllExercisesAsStrings() it doesn't update.

class GenerateCustom extends ExerciseListState {
  int rnd;

  GenerateCustom({this.difficulty});
  final int difficulty;
  String workout;
  String ex1;
  String ex2;
  String ex3;
  String ex4;
  String ex5;

  List customExercises = [];

  //get list of custom workouts
  List getAllExercisesAsStrings(customExercises) {
    var n;
    for (n = 0; n < exerciseList.length; n++) {
//      print(exerciseList[n].title);
      customExercises.add(exerciseList[n].title);
    }
    return customExercises;
  }

For context the getCustomType() gets a random exercise from the list to be displayed.

String getCustomType() {
    var random = Random();
    var i = random.nextInt(customExercises.length);
    print(customExercises[i]);
    return customExercises[i];
  }

  String cExerciseOne() {
    if (difficulty == 1) {
      workout =
          ('1: ' + getCustomType() + ' ' + getRepsEasy() + 'x' + getSetsEasy());
    } else if (difficulty == 2) {
      workout = ('1: ' +
          getCustomType() +
          ' ' +
          getRepsMedium() +
          'x' +
          getSetsMedium());
    } else {
      workout =
          ('1: ' + getCustomType() + ' ' + getRepsHard() + 'x' + getSetsHard());
    }
    return workout;
  }

---

When I print to console exerciseList[n].title it returns the list with the exercises eg ['exercise1','Bicep Curl', 'Pull Up', ] etc. These exercises have already been retrieved in the parent class and I would like to store them in the new list. Any guidance would be great and if you think more context is needed let me know.

Answer 1

The reason why List customExercises isn't populated is because customExercises.add() is being called inside a Stateful Widget. To add new Objects to the List, you'd need to call setState() when an item is added.

setState(() {
  customExercises.add(exerciseList[n].title);
});