Classes in Dart

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Dart Object Oriented Programming Class Tutorial and Example.

We will explore classes in this tutorial.

Let's start by looking at various implementations to get a feeling of classes in dart.

Let's say we want to reprsent a single Employee with his details.

class Employee {
  String firstName;
  String lastName;
  String mobileNo;
  String emailId;

  Employee(this.firstName, this.lastName, this.mobileNo, this.emailId);
  Employee.fromMap(Map map) {
    firstName = map[firstName];
    lastName = map[lastName];
    mobileNo = map[mobileNo];
    emailId = map[emailId];
  }
}

Here's another example:

class Name {
  String firstName;
  String lastName;
  Map<String, dynamic> toMap() {
    return {
      'firstName': firstName,
      'lastName': lastName
    };
  }

  String toString() => "$firstName $lastName";
}

Here's another example to represent a todo:

class Todo {
  int _id;
  String _title;
  String _description;
  String _date;
  int _priority;

  Todo(this._title, this._priority, this._date, [this._description]);
  Todo.withId(this._id, this._title, this._priority, this._date, [this._description]);

  int get id => _id;
  String get title => _title;
  String get description => _description;
  int get priority => _priority;
  String get date => _date;

  set title(String newTitle) {
    if (newTitle.length <= 255) {
      _title = newTitle;
    }
  }

  set description(String newDescription) {
    if (newDescription.length <= 255) {
      _description = newDescription;
    }
  }

  set priority(int newPriority) {
    if (newPriority >= 0 && newPriority <= 3) {
      _priority = newPriority;
    }
  }

  set date(String newDate) {
    _date = newDate;
  }

  Map<String, dynamic> toMap(){
    var map = Map<String, dynamic>();
    map["title"] = _title;
    map["description"] = _description;
    map["priority"] = _priority;
    map["date"] = _date;
    if(_id != null){
      map["id"] = _id;
    }
    return map;
  }

  Todo.fromObject(dynamic o){
    this._id = o["id"];
    this._title = o["title"];
    this._description = o["description"];
    this._priority = o["priority"];
    this._date = o["date"];
  }

}

You create an abstract class using the abstract keyword:

abstract class AuthStateListener {
  void onAuthStateChanged(AuthState state);
}

NB/= More examples and explanations coming soon.

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