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INTUWeakForwarder.h
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INTUWeakForwarder.h
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//
// INTUWeakForwarder.h
//
// Created by Jeff Shulman and Dan Rowley on 3/14/14.
// Copyright (c) 2014 Intuit Inc
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
// "weak" references are great to use for delegate properties since they will automatically
// get nil'ed out when the delegate object goes away. Alas it turns out Apple doesn't use
// real weak references in its SDK but has all delegate properties as unsafe-unretained.
//
// This means the app will crash should the programmer forget to nil out all the delegate
// properties on dealloc and that delegate is called.
//
// So what this little NSProxy class does is store the delegate as a *real* weak reference
// and forwards all method invocations to it as long as it exists. When the delegate is
// dealloc'ed the real weak reference will be nil and nothing will be forwarded along.
//
// The NSProxy instance is stored using an associated object on the delegatee so when that goes
// away the proxy instance will too. So generally this should be the object you are setting
// the delegate property of.
//
// Instead of writing:
//
// <someinstance>.delegate = self;
//
// you write:
//
// <someinstance>.delegate = [INTUWeakForwarder forwardTo:self associatedWith:<someinstance>];
//
// E.g.:
//
// UIScrollView *scrollView = ...;
// scrollView.delegate = [INTUWeakForwarder forwardTo:self associatedWith:scrollView];
#import <Foundation/Foundation.h>
@interface INTUWeakForwarder : NSProxy
/// Factory for NSProxy forwarding object
///
/// @param theRealDelegate The delegate instance object
/// @param object The object to tie the lifetime of the proxy object to
/// @return The proxy object to assign as the delegate object
+(id)forwardTo:(id)theRealDelegate associatedWith:(id)object;
@end