Flutter map.addAll() results in failure - dart

Question

I got the following List<Map> in Flutter:
List<Map<String, dynamic>> recipeList = [
{
'name': 'rec1',
'id': 1,
'img': 'images/recipe.jpg',
'ingredients': [{
'name': 'salt',
'amount': '1',
'unit': '1',
},
{
'name': 'flour',
'amount': '100',
'unit': 'g',
},
{
'name': 'water',
'amount': '100',
'unit': 'g',
},
{
'name': 'milk',
'amount': '100',
'unit': 'g',
},],
},]
I pass it down through several Widgets and at some point I want to add the key value pair {'didBuy':false} to every Map inside the ingredients list (which is basically recipeList['ingredients']).
Thus I call:
List<Map<String, dynamic>> resultList = recipeList['ingredients'].map((elem) {
elem.addAll({'didBuy': false});
print(elem);
}).toList();
Unfortunately the following error message results: Dart Error: Unhandled exception:type '_InternalLinkedHashMap<String, bool>' is not a subtype of type 'Map<String, String>' of 'other'.
Does anybody know what is the correct way to add something to a map, without getting this error message?
Edited the question to be more precise.
EDIT2:
After calling the type of the List explicitly inside the Map as Hadrien suggested, I can add the key value pair with the boolean. Long term I want to fetch the data from the Internet, so I defined a RecipeObj:
class RecipeObj{
String name;
int id;
String img;
List<Map<String, dynamic>> ingredients;
RecipeObj(this.name, this.id, this.img, this.ingredients);
}
Here I explicitly state the type of the ingredients attribute, so I thought I could get of the explicit calling inside the (main) recipeList. But after passing the ingredients attribute down through some widgets, flutter recognizes it as List<Map<String, String>>, although I define it everywhere as an List<Map<String, dynamic>>, why is that?

Answer 1

dart infer the type of your ingredients list with Map<String, String>
you can specify the type by yourself inside your list
'ingredients': <Map<String, dynamic>>[ {
'name': 'salt',
'amount': '1',
'unit': '1',
},
or build a new Map<String, dynamic> inside your map function
List<Map<String, dynamic>> resultList = recipeList['ingredients'].map((elem) {
final map = Map<String, dynamic>.from(elem);
map.addAll({'didBuy': false});
return map;
}).toList();

Answer 2

This should do
List<Map<String,dynamic>> recipeList = [
at least if recipeList and ingredients point at the same collection instance.
var ingredients = recipeList;

Answer 3

Is this what you need?
void main() {
List<Map> recipeList = [
{
'name': 'rec1',
'id': 1,
'img': 'images/recipe.jpg',
'ingredients': [{
'name': 'salt',
'amount': '1',
'unit': '1',
},
{
'name': 'flour',
'amount': '100',
'unit': 'g',
},
{
'name': 'water',
'amount': '100',
'unit': 'g',
},
{
'name': 'milk',
'amount': '100',
'unit': 'g',
},]
},];
print("[DATA BEFORE ANY CHANGE]");
print("recipeList.length=${recipeList.length}");
print("recipeList[0][\"ingredients\"]=${recipeList[0]["ingredients"]}");
print("recipeList[0][\"ingredients\"].last=${recipeList[0]["ingredients"].last}");
print("recipeList[0][\"ingredients\"].length=${recipeList[0]["ingredients"].length}");
// no recipe is worth if it doesn't contain chocolate
recipeList[0]["ingredients"].add({
'name': 'cocoa powder',
'amount': '200',
'unit': 'g',
});
print("\n\n[DATA AFTER ADD]");
print("recipeList[0][\"ingredients\"].last=${recipeList[0]["ingredients"].last}");
print("recipeList[0][\"ingredients\"].length=${recipeList[0]["ingredients"].length}");
}
OUTPUT
[DATA BEFORE ANY CHANGE]
recipeList.length=1
recipeList[0]["ingredients"]=[{name: salt, amount: 1, unit: 1}, {name: flour, amount: 100, unit: g}, {name: water, amount: 100, unit: g}, {name: milk, amount: 100, unit: g}]
recipeList[0]["ingredients"].last={name: milk, amount: 100, unit: g}
recipeList[0]["ingredients"].length=4
[DATA AFTER ADD]
recipeList[0]["ingredients"].last={name: cocoa powder, amount: 200, unit: g}
recipeList[0]["ingredients"].length=5