Question

我有以下地图

Map testMap = { 
  3 : {
    'order': 3,
    'sample' : 'sample'
  },
  2 : {
    'order': 2,
    'sample' : 'sample'
  },
  1 : {
    'order': 1,
    'sample' : 'sample'
  },
  4: {
    'order': 4,
    'sample' : 'sample'
  }
};

我如何按键对其进行排序，如果订单不可能按顺序排序＆＃39;子图中的值。

注意：地图最多可增加100个字段。

解决我以前一定很累，但以防其他人在这里寻找是我的解决方案。另外，用SplayTreeMap按键排序会产生一个奇怪的顺序，如1,10,11,12,13,14,15,16,17,18,19,2,20,21 ......

import 'dart:collection';

void main() {
  Map testMap = {
     11: {
      'order': '11',
      'sample' : 'sample'
    },
    3 : {
      'order': '3',
      'sample' : 'sample'
    },
    2 : {
      'order': '2',
      'sample' : 'sample'
    },
    1 : {
      'order': '1',
      'sample' : 'sample'
    },
    4: {
      'order': '4',
      'sample' : 'sample'
    },
    31: {
      'order': '31',
      'sample' : 'sample'
    },
    21: {
      'order': '21',
      'sample' : 'sample'
    }
  };

  final sorted = new SplayTreeMap.from(testMap, (a, b) => int.parse(testMap[a]['order']).compareTo(int.parse(testMap[b]['order'])));

  print(sorted);
}

Answer 1

import 'package:queries/collections.dart';

void main() {
  var d = Dictionary.fromMap(testMap);
  // Sort by key
  var q = d
      .orderBy((kv) => kv.key)
      .toDictionary$1((kv) => kv.key, (kv) => kv.value);
  print(q.toMap());
  // Sort by the value 'order' in reverse order
  q = d
      .orderByDescending((kv) => int.parse(kv.value['order']))
      .toDictionary$1((kv) => kv.key, (kv) => kv.value);
  print(q.toMap());
}

var testMap = {
  11: {'order': '11', 'sample': 'sample'},
  3: {'order': '3', 'sample': 'sample'},
  2: {'order': '2', 'sample': 'sample'},
  1: {'order': '1', 'sample': 'sample'},
  4: {'order': '4', 'sample': 'sample'},
  31: {'order': '31', 'sample': 'sample'},
  21: {'order': '21', 'sample': 'sample'}
};

结果：

{1: {order: 1, sample: sample}, 2: {order: 2, sample: sample}, 3: {order: 3, sample: sample}, 4: {order: 4, sample: sample}, 11: {order: 11, sample: sample}, 21: {order: 21, sample: sample}, 31: {order: 31, sample: sample}} {31: {order: 31, sample: sample}, 21: {order: 21, sample: sample}, 11: {order: 11, sample: sample}, 4: {order: 4, sample: sample}, 3: {order: 3, sample: sample}, 2: {order: 2, sample: sample}, 1: {order: 1, sample: sample}}

Answer 2

有关根据其值对Map进行排序的示例代码

vector<std::unique_ptr<Foo>> my_vector;

void setFoo(Foo foo) {
    my_vector.emplace_back(std::make_unique<Foo>(foo));
}

按键或按值对Dart中的地图进行排序

2 个答案: