what is the easiest way to merge 2 list of object in flutter dart? - list

Question

what is the easiest way to merge 2 list of object in flutter dart and achieve the result?
List 1
[
{name: eat, frequency: Daily},
{name: read, frequency: Daily},
{name: walk, frequency: Daily,}
]
List 2
[
{name: eat, count: 2},
{name: read, count: 2},
{name: walk, count: 2,}
]
Result
[
{name: eat, count: 2, frequency: Daily},
{name: read, count: 2, frequency: Daily},
{name: walk, count: 2, frequency: Daily}
]

Answer 1

Assuming the lists have the same length and contain Maps:
void main() {
var l1 = [
{'name': 'eat', 'frequency': 'Daily'},
{'name': 'read', 'frequency': 'Daily'},
{'name': 'walk', 'frequency': 'Daily'}
];
var l2 = [
{'name': 'eat', 'count': 2},
{'name': 'read', 'count': 2},
{'name': 'walk', 'count': 2}
];
var l3 = [
for (var i = 0; i < l1.length; i++) {...l1[i], ...l2[i]},
];
print(l3);
// [{name: eat, frequency: Daily, count: 2}, {name: read, frequency: Daily, count: 2}, {name: walk, frequency: Daily, count: 2}]
}

Answer 2

There are several simple ways to combine these lists, but they run into several issues. For example, can you guarantee that the lists will be the same length and that the order of the lists will be identical (as far as the "name" field in the nested maps are concerned)?
If you can't guarantee equal length and matching order, then you need to resort to a slightly more complex approach that is agnostic to either of those issues.
void main() {
final list1 = [
{'name': 'eat', 'frequency': 'Daily'},
{'name': 'read', 'frequency': 'Weekly'},
{'name': 'walk', 'frequency': 'Monthly'},
];
final list2 = [
{'name': 'walk', 'count': 4},
{'name': 'eat', 'count': 2},
{'name': 'read', 'count': 3},
];
// Convert the second list into a lookup table
final lookup = Map.fromIterable(list2, key: (m) => m['name'], value: (m) => m);
// Generate the combined list, using the first list as a base
final combined = list1.map((m) => { ...m, ...lookup[m['name']] }).toList();
print(combined);
// Prints (formatted)
// [
// {name: eat, count: 2, frequency: Daily},
// {name: read, count: 3, frequency: Weekly}
// {name: walk, count: 4, frequency: Monthly},
// ]
}