如何通过 Map 的特定键合并/加入两个 Map 列表？
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【中文标题】如何通过 Map 的特定键合并/加入两个 Map 列表？【英文标题】：How to merge/join two List of Map by specific key of Map? 【发布时间】：2021-02-25 15:56:07 【问题描述】：如何通过特定键合并两个 List
例如：
List
List<Map<String, dynamic>> Wallet = [
"id": 1,
"value": 153030
,
"id": 2,
"value": 817831
,
"id": 3,
"value": 25
,
"id": 4,
"value": 660
,
"id": 5,
"value": 132
,
"id": 7,
"value": 145
];
List<Map<String, dynamic>> Currencies = [
"id": 1,
"name": "coin",
"desc": "Dummytext.",
"order": 101,
"icon": "https://icon1.png"
,
"id": 2,
"name": "karma",
"desc": "Dummytext.",
"order": 102,
"icon": "https://icon2.png"
,
"id": 3,
"name": "laurel",
"desc": "Dummytext.",
"order": 104,
"icon": "https://icon3.png"
,
"id": 4,
"name": "diamonds",
"desc": "Dummytext.",
"order": 100,
"icon": "https://icon4.png"
,
"id": 5,
"name": "tears",
"desc": "Dummytext.",
"order": 402,
"icon": "https://icon5.png"
,
"id": 6,
"name": "shard",
"desc": "Dummytext.",
"order": 409,
"icon": "https://icon6.png"
,
"id": 7,
"name": "relict",
"desc": "Dummytext.",
"order": 400,
"icon": "https://icon7.png"
,
"id": 9,
"name": "seal",
"desc": "Dummytext.",
"order": 403,
"icon": "https://icon9.png"
,
"id": 10,
"name": "silver",
"desc": "Dummytext.",
"order": 405,
"icon": "https://icon10.png"
];
合并后的列表我要找的操作后
List<Map<String, dynamic>> ExtendedWallet = [
"id": 1,
"value": 153030,
"name": "coin",
"desc": "Dummytext.",
"order": 101,
"icon": "https://icon1.png"
,
"id": 2,
"value": 817831,
"name": "karma",
"desc": "Dummytext.",
"order": 102,
"icon": "https://icon2.png"
,
"id": 3,
"value": 25,
"name": "laurel",
"desc": "Dummytext.",
"order": 104,
"icon": "https://icon3.png"
,
"id": 4,
"value": 660,
"name": "diamonds",
"desc": "Dummytext.",
"order": 100,
"icon": "https://icon4.png"
,
"id": 5,
"value": 132,
"name": "tears",
"desc": "Dummytext.",
"order": 402,
"icon": "https://icon5.png"
,
"id": 7,
"value": 145,
"name": "relict",
"desc": "Dummytext.",
"order": 400,
"icon": "https://icon7.png"
];
请注意，“id”在 Wallet 中 not 的 Currencies 地图将不会被使用，将被跳过。
希望你们能得到我的意见，并能帮助我解决这个问题！
【问题讨论】：
【参考方案1】：你可以使用singleWhere找到cross id，然后使用map进行合并，这里修复的问题是飞镖垫here
List<Map<String, dynamic>> wallet = [
"id": 1, "value": 153030,
"id": 2, "value": 817831,
"id": 3, "value": 25,
"id": 4, "value": 660,
"id": 5, "value": 132,
"id": 7, "value": 145
];
List<Map<String, dynamic>> currencies = [
"id": 1,
"name": "coin",
"desc": "Dummytext.",
"order": 101,
"icon": "https://icon1.png"
,
"id": 2,
"name": "karma",
"desc": "Dummytext.",
"order": 102,
"icon": "https://icon2.png"
,
"id": 3,
"name": "laurel",
"desc": "Dummytext.",
"order": 104,
"icon": "https://icon3.png"
,
"id": 4,
"name": "diamonds",
"desc": "Dummytext.",
"order": 100,
"icon": "https://icon4.png"
,
"id": 5,
"name": "tears",
"desc": "Dummytext.",
"order": 402,
"icon": "https://icon5.png"
,
"id": 6,
"name": "shard",
"desc": "Dummytext.",
"order": 409,
"icon": "https://icon6.png"
,
"id": 7,
"name": "relict",
"desc": "Dummytext.",
"order": 400,
"icon": "https://icon7.png"
,
"id": 9,
"name": "seal",
"desc": "Dummytext.",
"order": 403,
"icon": "https://icon9.png"
,
"id": 10,
"name": "silver",
"desc": "Dummytext.",
"order": 405,
"icon": "https://icon10.png"
];
var result = currencies.map((e)
Map<String, dynamic> founded =
wallet.singleWhere((w) => w['id'] == e['id'], orElse: ()return null;);
if (founded != null)
e.addEntries(founded.entries);
return e;
else
return null;
).toList();
print(result);
【讨论】：
好吧，不知何故它不起作用。最后尝试使用您的打印语句验证输出，但它什么也没做。此外，“as Map您可以使用此代码获得所需的结果
import 'dart:convert';
void main()
List<Map<String, dynamic>> Wallet = [
"id": 1,
"value": 153030
,
"id": 2,
"value": 817831
,
"id": 3,
"value": 25
,
"id": 4,
"value": 660
,
"id": 5,
"value": 132
,
"id": 7,
"value": 145
];
List<Map<String, dynamic>> Currencies = [
"id": 1,
"name": "coin",
"desc": "Dummytext.",
"order": 101,
"icon": "https://icon1.png"
,
"id": 2,
"name": "karma",
"desc": "Dummytext.",
"order": 102,
"icon": "https://icon2.png"
,
"id": 3,
"name": "laurel",
"desc": "Dummytext.",
"order": 104,
"icon": "https://icon3.png"
,
"id": 4,
"name": "diamonds",
"desc": "Dummytext.",
"order": 100,
"icon": "https://icon4.png"
,
"id": 5,
"name": "tears",
"desc": "Dummytext.",
"order": 402,
"icon": "https://icon5.png"
,
"id": 6,
"name": "shard",
"desc": "Dummytext.",
"order": 409,
"icon": "https://icon6.png"
,
"id": 7,
"name": "relict",
"desc": "Dummytext.",
"order": 400,
"icon": "https://icon7.png"
,
"id": 9,
"name": "seal",
"desc": "Dummytext.",
"order": 403,
"icon": "https://icon9.png"
,
"id": 10,
"name": "silver",
"desc": "Dummytext.",
"order": 405,
"icon": "https://icon10.png"
];
List<Map<String, dynamic>> ExtendedWallet = [];
Currencies.forEach((element)
Wallet.forEach((e)
if(e["id"]==element["id"])
ExtendedWallet.add(
getExtendedWallet(e["id"]
,e["value"]
,element["name"]
,element["desc"],
element["order"],
element["icon"])
);
);
);
print(json.encode(ExtendedWallet).toString());
Map<String, dynamic> getExtendedWallet(int id,int value,String name,String desc,int order,String icon)
final Map<String, dynamic> data = new Map<String, dynamic>();
data["id"] = id;
data["value"] = value;
data["name"] = name.toString();
data["desc"] = desc.toString();
data["order"] = order;
data["icon"] = icon.toString();
return data;
【讨论】：
完美运行！你能解释一下这个功能吗？以上是关于如何通过 Map 的特定键合并/加入两个 Map 列表？的主要内容，如果未能解决你的问题，请参考以下文章