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我發現了一些非常棒的代碼，來自Matt Gallagher，用於使用NSInvocation撤消工作。儘管現在管理層希望我們將ARC用於我們的所有代碼，現在我們將所有代碼轉換爲ARC。這最後一塊是剩下的。馬特，沒有時間做轉換，所以我希望能在這裏得到一些幫助。援助將NSInvocation代碼轉換爲ARC兼容（已經Objective-C）
任何援助將不勝感激！
謝謝！
NSInvocation的（ForwardedConstruction）.H
//
// NSInvocation(ForwardedConstruction).h
//
// Created by Matt Gallagher on 19/03/07.
// Copyright 2007 Matt Gallagher. All rights reserved.
//
// Permission is given to use this source code file without charge in any
// project, commercial or otherwise, entirely at your risk, with the condition
// that any redistribution (in part or whole) of source code must retain
// this copyright and permission notice. Attribution in compiled projects is
// appreciated but not required.
//
@interface NSInvocation (ForwardedConstruction)
+ (id)invocationWithTarget:(id)target
invocationOut:(NSInvocation **)invocationOut;
+ (id)retainedInvocationWithTarget:(id)target
invocationOut:(NSInvocation **)invocationOut;
@end
NSInvocation的（ForwardedConstuction）.M
//
// NSInvocation(ForwardedConstuction).m
//
// Created by Matt Gallagher on 19/03/07.
// Copyright 2007 Matt Gallagher. All rights reserved.
//
// Permission is given to use this source code file without charge in any
// project, commercial or otherwise, entirely at your risk, with the condition
// that any redistribution (in part or whole) of source code must retain
// this copyright and permission notice. Attribution in compiled projects is
// appreciated but not required.
//
#import "NSInvocation(ForwardedConstruction).h"
#import <objc/runtime.h>
#import <objc/message.h>
//
// InvocationProxy is a private class for receiving invocations via the
// forwarding mechanism and saving the received invocation to an external
// invocation pointer.
//
// To avoid as many instance methods as possible, InvocationProxy is a base
// class (not a subclass of NSObject) and does not implement the NSObject
// protocol (and so is *not* a first-class object).
//
@interface InvocationProxy
{
Class isa;
NSInvocation **invocation;
id target;
BOOL retainArguments;
NSUInteger forwardingAddress;
}
/*+ (id)alloc;*/
+ (void)setValuesForInstance:(InvocationProxy *)instance
target:(id)target
destinationInvocation:(NSInvocation **)destinationInvocation
retainArguments:(BOOL)retain;
- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector;
- (void)forwardInvocation:(NSInvocation *)forwardedInvocation;
@end
#ifndef __OBJC_GC__
//
// DeallocatorHelper is a basic object which takes an id
// and deallocates it when the DeallocatorHelper is deallocated.
//
// Not used in a garbage collected environment (which should deallocate the
// id automatically).
//
@interface DeallocatorHelper : NSObject
{
id object;
}
- (id)initWithObject:(id)newObject;
- (void)dealloc;
@end
@implementation DeallocatorHelper
//
// initWithObject
//
// Init method for objects which sets the id to be autoreleased.
//
- (id)initWithObject:(id)newObject
{
self = [super init];
if (self != nil)
{
object = newObject;
}
return self;
}
//
// dealloc
//
// Deallocates the id.
//
- (void)dealloc
{
NSDeallocateObject(object);
[super dealloc];
}
@end
#endif
@implementation InvocationProxy
//
// initialize
//
// This empty method is required because the runtime tries to invoke it when
// the first message is sent to the Class. If it doesn't exist, the runtime
// gets mad.
//
+ (void)initialize
{
}
//
// alloc
//
// Allocator for the class. Also sets the
//
+ (id)alloc
{
//
// Allocate the object using the default allocator.
//
InvocationProxy *newObject =
#ifdef __OBJC_GC__
objc_allocate_object(self, 0);
#else
NSAllocateObject(self, 0, nil);
#endif
return newObject;
}
- (id)init {
return self;
}
//
// setValuesForInstance:target:destinationInvocation:retainArguments:
//
// Method to set the attributes on the instance passed in. We use a class
// method instead of an instance method to avoid extra instance methods on
// the class.
//
+ (void)setValuesForInstance:(InvocationProxy *)instance
target:(id)destinationTarget
destinationInvocation:(NSInvocation **)destinationInvocation
retainArguments:(BOOL)retain;
{
instance->target = destinationTarget;
instance->invocation = destinationInvocation;
instance->retainArguments = retain;
}
//
// methodSignatureForSelector:
//
// Invoked by the runtime whenever a message is sent for a method that doesn't
// exist.
//
- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector
{
//
// This method should be invoked once before attributes are set (as an
// "init" invocation).
//
if (target == nil)
{
//
// If the invocation is something other than "init", complain using
// NSObject's standard doesNotRecognizeSelector:
//
if (aSelector != @selector(init))
{
SEL failSEL = @selector(doesNotRecognizeSelector:);
Method failMethod =
class_getInstanceMethod([NSObject class], failSEL);
IMP failImp = method_getImplementation(failMethod);
failImp(self, failSEL, aSelector);
}
//
// Otherwise, we use the forwarded "init" to preserve the return
// address of the forwarding code (which we can use later to determine
// if this is a forwarded or direct invocation).
//
forwardingAddress = (NSUInteger)__builtin_return_address(0);
//
// Return the NSMethodSignature from NSObject's init method (just
// so we have something to return).
//
return [NSObject instanceMethodSignatureForSelector:aSelector];
}
//
// On subsequent invocations, check if we are a forwarded invocation or
// a direct invocation.
//
NSUInteger returnAddress = (NSUInteger)__builtin_return_address(0);
if (returnAddress != forwardingAddress)
{
//
// Handle the case where methodSignatureForSelector: is the message sent
// directly to the proxy.
//
// There is a chance that we have guessed wrong (i.e. if this is sent
// from __forward__ but from a different code branch) but that won't
// cause a fatal problem, just a redundant autoreleased NSInvocation
// that will get safely autoreleased and ignored.
//
// Create an NSInvocation for methodSignatureForSelector:
//
NSMethodSignature *signature =
[target methodSignatureForSelector:_cmd];
*invocation =
[NSInvocation invocationWithMethodSignature:signature];
[*invocation setTarget:target];
[*invocation setSelector:_cmd];
[*invocation setArgument:&aSelector atIndex:2];
if (retainArguments)
{
[*invocation retainArguments];
}
//
// Deliberately fall through and still return the target's
// methodSignatureForSelector: result (in case we guessed wrong).
//
}
//
// This is the "normal" case: after initialization, we have been correctly
// invoked from the forwarding code. Return the target's
// methodSignatureForSelector: for the given selector.
//
NSMethodSignature *signature =
[target methodSignatureForSelector:aSelector];
NSAssert3(signature != nil,
@"NSInvocation(ForwardedConstruction) error: object 0x%@ of class '%@' does not implement %s",
target, [target className], sel_getName(aSelector));
return signature;
}
//
// forwardInvocation:
//
// This method is invoked by message forwarding.
//
- (void)forwardInvocation:(NSInvocation *)forwardedInvocation
{
//
// This method will be invoked once on initialization (before target is set).
// Do nothing.
//
if (target == nil)
{
//
// This branch will be followed when "init" is invoked on the newly
// allocated object. Since "init" returns "self" we need to set that
// on the forwardedInvocation.
//
[forwardedInvocation setReturnValue:&self];
return;
}
//
// Check if the target of the forwardedInvocation is equal to self. If
// it is, then this is a genuine forwardedInvocation. If it isn't, then
// forwardInvocation: was directly the message sent to this proxy.
//
if ([forwardedInvocation target] == self)
{
[forwardedInvocation setTarget:target];
*invocation = forwardedInvocation;
if (retainArguments)
{
[*invocation retainArguments];
}
return;
}
//
// Handle the case where forwardedInvocation is the message sent directly
// to the proxy. We create an NSInvocation representing a forwardInvocation:
// sent to the target instead.
//
NSMethodSignature *signature =
[target methodSignatureForSelector:_cmd];
*invocation =
[NSInvocation invocationWithMethodSignature:signature];
[*invocation setTarget:target];
[*invocation setSelector:_cmd];
[*invocation setArgument:&forwardedInvocation atIndex:2];
if (retainArguments)
{
[*invocation retainArguments];
}
}
@end
@implementation NSInvocation (ForwardedConstruction)
//
// invocationWithTarget:invocationOut:
//
// Basic constructor for NSIncoation using forwarded construction.
//
+ (id)invocationWithTarget:(id)target
invocationOut:(NSInvocation **)invocationOut
{
//
// Check that invocationOut isn't nil.
//
NSAssert2(target != nil && invocationOut != nil,
@"%@ method %s requires target that isn't nil and a valid NSInvocation** for the second parameter",
[self className], sel_getName(_cmd));
//
// Alloc and init the proxy
//
InvocationProxy *invocationProxy = [[InvocationProxy alloc] init];
//
// Set the instance attributes on the proxy
//
[InvocationProxy
setValuesForInstance:invocationProxy
target:target
destinationInvocation:invocationOut
retainArguments:NO];
//
// Create the DeallocatorHelper if needed
//
#ifndef __OBJC_GC__
[[[DeallocatorHelper alloc]
initWithObject:invocationProxy]
autorelease];
#endif
return invocationProxy;
}
//
// retainedInvocationWithTarget:invocationOut:
//
// Same as above but sends retainArguments to the NSInvocation created.
//
+ (id)retainedInvocationWithTarget:(id)target
invocationOut:(NSInvocation **)invocationOut
{
//
// Check that invocationOut isn't nil.
//
NSAssert2(target != nil && invocationOut != nil,
@"%@ method %s requires target that isn't nil and a valid NSInvocation** for the second parameter",
[self className], sel_getName(_cmd));
//
// Alloc and init the proxy
//
InvocationProxy *invocationProxy = [[InvocationProxy alloc] init];
//
// Set the instance attributes on the proxy
//
[InvocationProxy
setValuesForInstance:invocationProxy
target:target
destinationInvocation:invocationOut
retainArguments:YES];
//
// Create the DeallocatorHelper if needed
//
#ifndef __OBJC_GC__
[[[DeallocatorHelper alloc]
initWithObject:invocationProxy]
autorelease];
#endif
return invocationProxy;
}
@end