[英]How can I reorder or sort list of model based on another List of models with Dart?
[英]Sort a List in Dart based on how another List was sorted
我正在嘗試參考另一個列表對列表進行排序。 考慮這個例子,
List<String> a = ["a", "b", "c"];
List<int> b = [2, 3, 1];
現在,我希望結果是這樣的,
a = ["c", "a", "b"];
b = [1, 2, 3];
我怎樣才能達到這個結果?
您可以通過創建一個Map
來實現此目的,該Map
包含字母到數字的映射,即2
分配了a
字母, 3
分配了b
等。
現在,您可以正常地對列表進行排序,然后根據排序之前存儲的映射重新創建其他列表:
main() {
List<String> letters = ["a", "b", "c"];
final List<int> numbers = [2, 3, 1];
final Map<int, String> mappings = {
for (int i = 0; i < numbers.length; i++)
numbers[i]: letters[i]
};
numbers.sort();
letters = [
for (int number in numbers) mappings[number]
];
print(letters); // [c, a, b]
print(numbers); // [1, 2, 3]
}
在此示例中,我使用了集合 。 Dart 2.3
中引入了用於集合文字的語法。
了解更多 。
您可以輕松地將其轉過來,然后將數字映射到您的字母。 看起來像這樣:
main() {
final List<String> letters = ["a", "b", "c"];
List<int> numbers = [2, 3, 1];
final Map<String, int> mapping = {
for (int i = 0; i < letters.length; i++)
letters[i]: numbers[i]
};
letters.sort((a, b) => b.compareTo(a));
numbers = [
for (String letter in letters) mapping[letter]
];
print(letters); // [c, b, a]
print(numbers); // [1, 3, 2]
}
請注意 ,我排序的字母按降序這里轉動有關compareTo
以及(默認a.compareTo(b)
所使用的List.sort
)。
如果您的List
有重復的元素,您將無法使用Map
。 我改為使用package:tuple
,然后使用相同的方法將兩個List
組合成一個List<Tuple2>
,對其進行排序,然后提取值:
import 'package:tuple/tuple.dart';
void main() {
var a = ["a", "b", "c", "d"];
var b = [2, 3, 1, 1];
var combined = <Tuple2<int, String>>[
for (var i = 0; i < b.length; i += 1) Tuple2(b[i], a[i]),
];
combined.sort((tuple1, tuple2) => tuple1.item1.compareTo(tuple2.item1));
for (var i = 0; i < combined.length; i += 1) {
a[i] = combined[i].item2;
b[i] = combined[i].item1;
}
print(a); // Prints: [c, d, a, b]
print(b); // Prints: [1, 1, 2, 3]
}
我用這種方式來解決問題:
List<String> strings = ["a", "b", "c", "c"];
List<int> numbers = [2, 3, 1, 0];
List<int> storeNumbers = List.from(numbers);
List<int> storeIndex = [];
//sorting numbers list
numbers.sort((a, b) => a.compareTo(b));
//get the index of numbers list elements before the sorting
for (int i = 0; i < numbers.length; i++) {
for (int j = 0; j < storeNumbers.length; j++) {
if (numbers[i] == storeNumbers[j]) {
storeIndex.add(j);
}
}
}
//generate a new string list based on the indexes we get
strings =
List.generate(strings.length, (index) => strings[storeIndex[index]]);
print(strings);//output:[c, c, a, b]
print(numbers);//output:[0, 1, 2, 3]
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