I have a list called selected list of type dynamic and it holds a list of objects, each objects contains from a teacher ID & index.
I want to check if this list contains the same Id & index, if it does i want to remove this object from the list.
here is my code ....
void addTeacher(int teacherId, int index) {
if (this.selectedList.contains({ **/// the problem is here** })) {
this.selectedList.remove({teacherId, index});
this.myColor = Colors.grey;
print('removed teacher => ${teacherId.toString()}');
} else {
this.selectedList.add({teacherId, index});
this.myColor = AsasColors().blue;
print('added teacher => ${teacherId.toString()}');
}
notifyListeners();
print(selectedList);
}
how can i achive this ?
CodePudding user response:
Contains and remove use the == operator which in this case will return false because unless you override it for a specific class it will compare by reference. You can use indexWhere to find out if an item is in a list based on a compare function like that (if the function returns -1 the item is not on the list:
// Index different than -1 means the item is found somewhere in the list
final teacherIndex = this.selectedList.indexWhere((teacher) => teacher['teacherId'] == teacherId);
if (teacherIndex != -1) {
this.selectedList.removeAt(teacherIndex);
this.myColor = Colors.grey;
print('removed teacher => ${teacherId.toString()}');
} else {
...
}
CodePudding user response:
I have implemented it and it worked fine
[The code]
[The output:]
This is the written code:
class Subject {
int? teacherID;
int? subjectID;
Subject(this.teacherID, this.subjectID);
@override
String toString() => "Subject {teacherID: $teacherID, subjectID: $subjectID";
//TODO: Change your needed criteria here..
@override
bool operator ==(Object other) =>
other is Subject &&
teacherID == other.teacherID &&
subjectID == other.subjectID;
}
void addSubject(List<Subject> list, Subject subject) {
if (list.contains(subject)) {
list.remove(subject);
} else {
list.add(subject);
}
}
void main() {
List<Subject> selectedList =
List.generate(10, (index) => Subject(index 1, index 1));
print("SelectedList = $selectedList");
addSubject(selectedList, Subject(11, 11));
addSubject(selectedList, Subject(11, 12));
addSubject(selectedList, Subject(12, 11));
addSubject(selectedList, Subject(12, 12));
print("SelectedList2 = $selectedList");
addSubject(selectedList, Subject(12, 12));
print("SelectedList3 = $selectedList");
}
Sincerely, accept the answer if it worked for you.