From e2f13e166b73d06cdf938de786789e2e9a80fac5 Mon Sep 17 00:00:00 2001
From: ryohey <info@codingcafe.jp>
Date: Sun, 9 Jun 2019 00:25:07 +0900
Subject: [PATCH] Add Dictionary.removeEmpty()

---
 .../ProjectSpec/CollectionExtensions.swift    | 33 +++++++++++++++++++
 1 file changed, 33 insertions(+)
 create mode 100644 Sources/ProjectSpec/CollectionExtensions.swift

diff --git a/Sources/ProjectSpec/CollectionExtensions.swift b/Sources/ProjectSpec/CollectionExtensions.swift
new file mode 100644
index 00000000..40803a24
--- /dev/null
+++ b/Sources/ProjectSpec/CollectionExtensions.swift
@@ -0,0 +1,33 @@
+import Foundation
+
+private protocol EmptyRemovable {
+    func removeEmpty() -> Self
+    var isEmpty: Bool { get }
+}
+
+extension Array: EmptyRemovable {
+    public func removeEmpty() -> Array {
+        return compactMap {
+            if let e = ($0 as? EmptyRemovable)?.removeEmpty() {
+                return e.isEmpty ? nil : e as? Element
+            }
+            return $0
+        }
+    }
+}
+
+extension Dictionary: EmptyRemovable {
+    // this is a little trick that defines the generics parameter from optional Value to unwrapped Value
+    private static func removeEmpty<Key, Value>(dict: Dictionary<Key, Value?>) -> Dictionary<Key, Value> {
+        return dict.compactMapValues {
+            if let e = ($0 as? EmptyRemovable)?.removeEmpty() {
+                return e.isEmpty ? nil : e as? Value
+            }
+            return $0
+        }
+    }
+
+    public func removeEmpty() -> Dictionary<Key, Value> {
+        return Dictionary.removeEmpty(dict: self)
+    }
+}