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[英]How to filter id from json list and store in another list in flutter?
[英]How to get a list of highest values from another list in flutter
我有一個包含 5 個對象的玩家列表。
"data": [
{
"id": 74,
"name": "name 1",
"type": "defender",
"value": 10
},
{
"id": 7422,
"name": "name 2",
"type": "defender",
"value": 20
},
{
"id": 2213,
"name": "Max",
"type": "defender",
"value": 30
},
{
"id": 3333,
"name": "John",
"type": "defender",
"value": 40
},
{
"id": 8793,
"name": "Alex",
"type": "defender",
"value": 50
}
]
如何獲取包含數據列表中最高值的 3 項的列表?
預期結果 => [Max, John, Alex]
我只需要基於最高價值的前 3 項
你為什么不按值對這個列表進行排序,然后從列表中取出前三個值。
首先根據值對數據進行排序,然后找出最大值
void main() {
List<Map<String, dynamic>> data = [
{"id": 74, "name": "name 1", "type": "defender", "value": 10},
{"id": 7422, "name": "name 2", "type": "defender", "value": 20},
{"id": 2213, "name": "Max", "type": "defender", "value": 30},
{"id": 3333, "name": "John", "type": "defender", "value": 40},
{"id": 8793, "name": "Alex", "type": "defender", "value": 50}
];
// sort the data based on
if (data != null && data.isNotEmpty) {
data.sort((a, b) => a['value'].compareTo(b['value']));
}
// you can simply do this
for( int i =data.length-3; i< data.length;i++){
print(data[i]["name"]);
}
// truncate the max value from the bottom part
List<Map<String, dynamic>> data1 = data.sublist(data.length-3, data.length);
// show the data whom hold the max value
data1.reversed.forEach((e){
print(e["name"]);
});
}
Output:亞歷克斯·約翰·馬克斯
注意:如果要在獲得排序值后從高到低打印,則使用 reversed
List<Map<String, dynamic>> users =[
{
"id": 74,
"name": "name 1",
"type": "defender",
"value": 10
},
{
"id": 7422,
"name": "name 2",
"type": "defender",
"value": 20
},
{
"id": 2213,
"name": "Max",
"type": "defender",
"value": 30
},
{
"id": 3333,
"name": "John",
"type": "defender",
"value": 40
},
{
"id": 8793,
"name": "Alex",
"type": "defender",
"value": 50
}
]
if (users != null && users.isNotEmpty) {
users.sort((a, b) => a['value'].compareTo(b['value']));
print(users.last['value']);
用戶列表已經在上面的代碼中排序。 所以列表的最后 3 項是最大值!
對我來說,如果您有一個標准,即 20 或 30 的值更高
List<Map<String,dynamic>> items = [{
"id": 74,
"name": "name 1",
"type": "defender",
"value": 10
},
{
"id": 7422,
"name": "name 2",
"type": "defender",
"value": 20
},
{
"id": 2213,
"name": "Max",
"type": "defender",
"value": 30
},
{
"id": 3333,
"name": "John",
"type": "defender",
"value": 40
},
{
"id": 8793,
"name": "Alex",
"type": "defender",
"value": 50
}];
然后對它們進行排序就像這樣
items.where((e) => e['value'] > 20).toList()..sort((a,b)=>b['value'].toString().compareTo(a['value'].toString()));
你會得到一組另外的數據
[
{id: 8793, name: Alex, type: defender, value: 50},
{id: 3333, name: John, type: defender, value: 40},
{id: 2213, name: Max, type: defender, value: 30}
]
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