Flutter : How change modify unmodifiable map - flutter

Question

I have list like this in provider:
List orders=[]:
void getOrders(){
orders = [
{"id":1,
"order":[
{"id":1,"name":"mike"},
{"id":2,"name":"john"},
{"id":3,"name":"smith"}
]
},
{"id":1,
"order":[
{"id":1,"name":"roz"},
{"id":2,"name":"sam"},
{"id":3,"name":"ruby"}
]
},
];
notifyListeners();
}
in provider when I use this methos to chane indexed order with another:
void changeOrder(orderIndex,item){
orders[orderIndex].update("order",(val)=>item);
notifyListeners();
}
I get this error type '(dynamic) => dynamic' is not a subtype of type '(Object) => Object' of 'update'
and when I use this :
void changeOrder(orderIndex,item){
orders[orderIndex]["order"]=item;
notifyListeners();
}
I get this error Unsupported operation: Cannot modify unmodifiable map
Add More Details
the item in changeOrder method comes from screen contain orders :
var item = List.from(orders[index]);

Answer 1

orders type is List<Map<String, dynamic>>. While reading the item, it will be a map instead of list.
Map item = Map.from(orders[index]);
And you can use both way you;ve tried.
List<Map<String, dynamic>> orders = [];
void getOrders() {
orders = [
{
"id": 1,
"order": [
{"id": 1, "name": "mike"},
{"id": 2, "name": "john"},
{"id": 3, "name": "smith"}
]
},
{
"id": 1,
"order": [
{"id": 1, "name": "roz"},
{"id": 2, "name": "sam"},
{"id": 3, "name": "ruby"}
]
},
];
}
void changeOrder(orderIndex, item) {
orders[orderIndex]["order"] = item;
// orders[orderIndex].update("order", (val) => item);
}
void main(List<String> args) {
getOrders();
print(orders);
Map item = Map.from(orders[1]);
changeOrder(1, item);
print(orders);
}