From 06c2fc97ad7cc6a59168e5995894167100a4cf6f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Krist=C3=B3f=20T=C3=B3th?= <kristof.toth@avatao.com>
Date: Fri, 1 Jun 2018 13:58:50 +0200
Subject: [PATCH] Implement decorator to lazy initialise a property

---
 lib/tfw/decorators/__init__.py        |  1 +
 lib/tfw/decorators/lazy_initialise.py | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+)
 create mode 100644 lib/tfw/decorators/lazy_initialise.py

diff --git a/lib/tfw/decorators/__init__.py b/lib/tfw/decorators/__init__.py
index 80c5788..cd61318 100644
--- a/lib/tfw/decorators/__init__.py
+++ b/lib/tfw/decorators/__init__.py
@@ -2,3 +2,4 @@
 # All Rights Reserved. See LICENSE file for details.
 
 from .rate_limiter import RateLimiter
+from .lazy_initialise import LazyInitialise
diff --git a/lib/tfw/decorators/lazy_initialise.py b/lib/tfw/decorators/lazy_initialise.py
new file mode 100644
index 0000000..615721b
--- /dev/null
+++ b/lib/tfw/decorators/lazy_initialise.py
@@ -0,0 +1,19 @@
+# Copyright (C) 2018 Avatao.com Innovative Learning Kft.
+# All Rights Reserved. See LICENSE file for details.
+
+
+class LazyInitialise:
+    """
+    Decorator that replaces a function with the value
+    it calculates on the first call.
+    """
+    def __init__(self, func):
+        self.func = func
+        self.__doc__ = func.__doc__
+
+    def __get__(self, instance, owner):
+        if instance is None:
+            raise TypeError('Cannot get object property from class!')
+        value = self.func(instance)
+        setattr(instance, self.func.__name__, value)
+        return value