Create compactmap-on-map-in-dart.dart

tipsandtricks/compactmap-on-map-in-dart/compactmap-on-map-in-dart.dart

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+
+import 'dart:developer' as dev show log;
+
+// log
+extension Log on Object {
+  void log() {
+    dev.log(toString());
+  }
+}
+
+extension CompactMap<K, V> on Map<K, V> {
+  Map<K2, V2> compactMap<K2, V2>(
+    MapEntry<K2, V2>? Function(MapEntry<K, V>) f,
+  ) {
+    final result = <K2, V2>{};
+    for (final entry in entries) {
+      final newEntry = f(entry);
+      if (newEntry != null) {
+        result[newEntry.key] = newEntry.value;
+      }
+    }
+    return result;
+  }
+}
+
+final values = {
+  'first_name': 'Foo',
+  'last_name': 'Bar',
+  'age': 22,
+};
+
+void testIt() {
+  values.compactMap((entry) {
+    if (entry.key == 'age') {
+      return null;
+    } else {
+      return MapEntry(
+        entry.key.toUpperCase(),
+        entry.value,
+      );
+    }
+  }).log(); // {FIRST_NAME: Foo, LAST_NAME: Bar}
+}