Implements Objective C delegate support

examples/delegate.py

@@ -0,0 +1,44 @@
+"""
+This example simplifies the code from the URL Loading System Programming Guide
+(http://goo.gl/JJ2Q8T). It uses NSURLConnection to request an invalid connection
+and get the connection:didFailWithError: delegate method triggered.
+"""
+from kivy.app import App
+from kivy.uix.widget import Widget
+from pyobjus import autoclass, objc_delegate, objc_str
+from pyobjus.dylib_manager import load_framework, INCLUDE
+
+load_framework(INCLUDE.AppKit)
+load_framework(INCLUDE.Foundation)
+
+NSURL = autoclass('NSURL')
+NSURLConnection = autoclass('NSURLConnection')
+NSURLRequest = autoclass('NSURLRequest')
+
+
+class MyObjcDelegate:
+  """A delegate class implemented in Python."""
+
+  def connection_didFailWithError_(self, connection, error):
+    print("Protocol method got called!!", connection, error)
+
+
+def request_connection():
+    # This method request connection to an invalid URL so the
+    # connection_didFailWithError_ protocol method will be triggered.
+    url = NSURL.URLWithString_(objc_str('abc'))
+    request = NSURLRequest.requestWithURL_(url)
+    # Converts the Python delegate object to Objective C delegate instance
+    # simply by calling the objc_delegate() function.
+    delegate = objc_delegate(MyObjcDelegate(), ['NSURLConnectionDelegate'])
+    connection = NSURLConnection.connectionWithRequest_delegate_(request,
+                                                                 delegate)
+
+
+class DelegateApp(App):
+  def build(self):
+    request_connection()
+    return Widget()
+
+if __name__ == "__main__":
+    DelegateApp().run()