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47 lines
942 B
47 lines
942 B
4 months ago
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Map<S, List<T>> groupBy<S, T>(Iterable<T> values, S Function(T) key) {
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var map = <S, List<T>>{};
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for (var element in values) {
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(map[key(element)] ??= []).add(element);
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}
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return map;
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}
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Map<String, int> groupCount<S, T>(Map<S, List<T>> values) {
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var map = <String, int>{};
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for (var element in values.keys) {
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map["$element"] = values[element]?.length ?? 0;
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}
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return map;
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}
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Map<String, T> groupItem<S, T>(Map<S, List<T>> values) {
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var map = <String, T>{};
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for (var element in values.keys) {
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if (values[element] == null) {
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continue;
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}
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map["$element"] = values[element].first;
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}
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return map;
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}
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extension ListExtension<S, T> on Iterable<T> {
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Map<S, List<T>> lGroupBy(S Function(T) key) {
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return groupBy(this, key);
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}
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}
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extension MapExtension<S, T> on Map<S, List<T>> {
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Map<String, int> get mGroupCount => groupCount(this);
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Map<String, T> get mGroupItem => groupItem(this);
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}
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