1 files changed, 32 insertions, 0 deletions
diff --git a/src/app/pipes/guard-type.pipe.ts b/src/app/pipes/guard-type.pipe.ts
new file mode 100644
index 0000000..0c2b847
--- /dev/null
+++ b/src/app/pipes/guard-type.pipe.ts
@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2022. Deutsche Telekom AG
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+
+import { Pipe, PipeTransform } from '@angular/core';
+
+export type TypeGuard<A, B extends A> = (a: A) => a is B;
+
+// https://github.com/angular/angular/issues/34522#issuecomment-762973301
+@Pipe({
+  name: 'guardType',
+})
+export class GuardTypePipe implements PipeTransform {
+  transform<A, B extends A>(value: A, typeGuard: TypeGuard<A, B>): B | undefined {
+    return typeGuard(value) ? value : undefined;
+  }
+}