/*

 File: TestMethodReplacement.m

 Abstract:

 Objective C 2.0 Compatible class_poseAs() replacement. This

 demonstrates how to replace a method in an existing Objective C class,

 and how to call the old version without having to store IMP function

 pointers in a global. The trick is to define a category on the class

 whose method you want to replace. In the category, declare and

 implement a method with the same signature as the replaced method. In

 the +load method of the category, look up the original and replacement

 methods using class_getInstanceMethod(), then call

 method_exchangeImplementations(). Subsequent calls to the original

 method will call the replacement method, and an apparently recursive

 call to the replacement method will call the original method. Voila.

 Version: 1.0

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 Neither the name, trademarks, service marks or logos of Apple Computer,

 Inc. may be used to endorse or promote products derived from the Apple

 Software without specific prior written permission from Apple.  Except

 as expressly stated in this notice, no other rights or licenses, express

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 MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION

 THE IMPLIED WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS

 FOR A PARTICULAR PURPOSE, REGARDING THE APPLE SOFTWARE OR ITS USE AND

 OPERATION ALONE OR IN COMBINATION WITH YOUR PRODUCTS.

 IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL

 OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

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 */

#import <AppKit/AppKit.h>

#import <objc/runtime.h>

@interface NSWindow (TestMethodReplacement)

- (void)TestMethodReplacement_sendEvent:(NSEvent *)event;

@end

@implementation NSWindow (TestMethodReplacement)

+ (void)load {

    if (self == [NSWindow class]) {

        // Swap the implementations of -[NSWindow sendEvent:] and -[NSWindow TestMethodReplacement_sendEvent:].

        // When the -sendEvent: message is sent to an NSWindow instance, -TestMethodReplacement_sendEvent: will

        // be called instead. Calling [self TestMethodReplacement_sendEvent:event] thus calls the original method.

        Method originalMethod = class_getInstanceMethod(self, @selector(sendEvent:));

        Method replacedMethod = class_getInstanceMethod(self, @selector(TestMethodReplacement_sendEvent:));

        method_exchangeImplementations(originalMethod, replacedMethod);

    }

}

- (void)TestMethodReplacement_sendEvent:(NSEvent *)event {

    if ([event type] == NSLeftMouseDown && [event modifierFlags] & NSCommandKeyMask) {

        [NSAnimationContext beginGrouping];

        [[NSAnimationContext currentContext] setDuration:1.0];

        [[self animator] setAlphaValue:0.0];

        [NSAnimationContext endGrouping];

    } else {

        // Call the original sendEvent: method, whose implementation was exchanged with our own.

        // Note:  this ISN'T a recursive call, because this method should have been called through -sendEvent:.

        NSParameterAssert(_cmd == @selector(sendEvent:));

        [self TestMethodReplacement_sendEvent:event];

    }

}

@end