How to rearrange map keys in dart? - flutter

Question

I have a map like below :
{
"Future": [
{
"accountId": 57,
"firstName": "Inez",
"lastName": "Mitchell",
"middleName": "J",
}
],
"Overdue": [
{
"accountId": 5,
"firstName": "Mak",
"lastName": "Mitchell",
"middleName": "M",
}
],
"Due Today": [
{
"accountId": 59,
"firstName": "Jack",
"lastName": "Daniel",
"middleName": "P",
}
]
}
and wanted the map like in below order, Due Today first, Overdue 2nd and Future at last.
{
"Due Today": [
{
"accountId": 59,
"firstName": "Jack",
"lastName": "Daniel",
"middleName": "P",
}
],
"Overdue": [
{
"accountId": 5,
"firstName": "Mak",
"lastName": "Mitchell",
"middleName": "M",
}
],"Future": [
{
"accountId": 57,
"firstName": "Inez",
"lastName": "Mitchell",
"middleName": "J",
}
]
}
also these keys in length are 3 but sometimes we got only two of them means Due Today and Future but we have to make sure order is like 1. Due Today 2. Overdue 3. Future

Answer 1

There is no operation which simply rearranges the iteration order of a normal Dart map.
Dart maps usually default to using LinkedHashMap which orders its element (for example for iteration) in key insertion order.
If a key is already there, changing its value does not change the key's position in the iteration order, but any new key added will end up after all existing keys.
That provides the only avaialble way to change iteration order: Remove the key and add it again, which will put it at the end of the iteration order instead of where it previously was.
So, to reorder a map, the easiest is to create a new map:
var newMap = <String, List<Map<String, String>>>{};
for (var key in ["Due Today", "Overdue", "Future"]) {
if (map.containsKey(key)) newMap[key] = map[key];
}
Then newMap has the keys in the correct order. If you want to update your existing map to the same order, then you can do: map..clear()..addAll(newMap); afterwards.
If you want to avoid the extra map, you can delete keys and re-add them instead.
for (var key in ["Due Today", "Overdue", "Future"]) {
if (map.containsKey(key)) {
var value = map[key];
map.delete(key);
map[key] = value;
}
}
This should remove and re-add each key, if it's there at all, in the order you want them.

Answer 2

var keys = abc.keys.toList()..shuffle();
for(var k in keys) {
print('$k, ${abc[k]}');}

Answer 3

steps you need todo:
convert the map to a temp list
do your edits on the list
clear the map
copy the entries from the list back to map
**
> extension ExtensionsOnMap on Map<String, ChannelItem> {
> void replace(int index, String key, ChannelItem channelItem) {
>
> var tmpLst = this.entries.map((e) => MapEntry(e.key, e.value)).toList();
>
> tmpLst.removeAt(index);
> tmpLst.insert(index, new MapEntry(key, channelItem));
>
> this.clear();
>
> tmpLst.forEach((mapEntry) => this[mapEntry.key] = mapEntry.value);
> }
> }
**

Answer 4

Code:
void main(){
Map map = {
"Future": [
{
"accountId": 57,
"firstName": "Inez",
"lastName": "Mitchell",
"middleName": "J",
}
],
"Overdue": [
{
"accountId": 5,
"firstName": "Mak",
"lastName": "Mitchell",
"middleName": "M",
}
],
"Due Today": [
{
"accountId": 59,
"firstName": "Jack",
"lastName": "Daniel",
"middleName": "P",
}
]
};
for(String key in ['Due Today', 'Overdue', 'Future']){
var value = map[key];
map.remove(key);
map[key] = value;
}
print(map);
}
Output:
{
Due Today: [{
accountId: 59,
firstName: Jack,
lastName: Daniel,
middleName: P
}],
Overdue: [{
accountId: 5,
firstName: Mak,
lastName: Mitchell,
middleName: M
}],
Future: [{
accountId: 57,
firstName: Inez,
lastName: Mitchell,
middleName: J
}]
}