flutter create json or add list map - json

Question

I'm trying to create a custom json and with android java I can use json object and json array, but I couldn't find them in flutter. I created list <Map <String, String >> but when I add data it changes all indexes.
List<Map<String,String>> myList=[];
Map<String,String> mymap;
for(int i=0;i<5;i++){
mymap['name']='test'+i.toString();
myList.add(mymap);
print(myList[0]);// its always change test0,test1,test2
}
for (int i=0;i<5;i++){
print(myList[i]); // its write test5,test5,test5,test5,test5 why?
}

Answer 1

//pass your decoded json
Map<String, dynamic> json = jsonDecode(rawJson);
List<Location> locations = List<Location>.from(json["locations"].map((x) => Location.fromJson(x)))
//Location class => days is a premitive list and can be deserialized below
class Location {
Location({
this.name,
this.days,
});
String name;
List<int> days;
factory Location.fromJson(Map<String, dynamic> json) => Location(
name: json["name"],
days: List<int>.from(json["days"].map((x) => x)),
);
Map<String, dynamic> toJson() => {
"name": name,
"days": List<dynamic>.from(days.map((x) => x)),
};
}

Answer 2

When you assign variable to complex class it is passing reference not value, complex classes are those that you created and built in like List, Map ... etc
In this example in your List you are adding same Map 5 times,
and because it was passing reference same Map getting changed 5 times. I hope I make sense.
Here an example.
List<Map<String,String>> myList=[];
Map<String,String> mymap; // This created one object in the current scope.
// First iteration , i = 0
mymap['name']='test'+i.toString(); // Now mymap = { name: 'test0' };
myList.add(mymap); // mylist = [mymap];
// Second iteration , i = 1
mymap['name'] = 'test'+i.toString(); // Now mymap = { name: 'test1' };. But since you already added the same mymap in myList, now myList = [{ name: 'test1' }
myList.add(mymap); // This is again adding the same mymap. So mylist = [{ name: 'test1' }, { name: 'test1' }];