ReleaseLockProxy.m

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/*  ReleaseLockProxy.h
    By Jens Ayton
    This code is hereby placed in the public domain.
*/
 
#import "ReleaseLockProxy.h"
 
 
#define VERBOSE     0
 
#if VERBOSE
#define VerboseLog NSLog
#else
#define VerboseLog(...) do {} while (0)
#endif
 
 
@interface ReleaseLockProxy_SignatureTemplateClass: NSObject
 
// These exist purely to provide NSMethodSignatures for -[ReleaseLockProxy methodSignatureForSelector:].
+ (id)initWithObject:(id<NSObject>)object name:(NSString *)name;
+ (id)initWithRetainedObject:(id<NSObject>)object name:(NSString *)name;
+ (void)rlpAllowRelease;
+ (NSString *)rlpObjectDescription;
 
@end
 
 
@implementation ReleaseLockProxy
 
// *** Boilerplate
 
+ (id)proxyWithObject:(id<NSObject>)object name:(NSString *)name
{
    return [[[self alloc] initWithObject:object name:name] autorelease];
}
 
 
+ (id)proxyWithRetainedObject:(id<NSObject>)object name:(NSString *)name
{
    return [[[self alloc] initWithRetainedObject:object name:name] autorelease];
}
 
 
- (id)initWithObject:(id<NSObject>)object name:(NSString *)name
{
    return [self initWithRetainedObject:[object retain] name:name];
}
 
 
- (id)initWithRetainedObject:(id<NSObject>)object name:(NSString *)name
{
    if (object == nil)
    {
        NSLog(@"** ReleaseLockProxy: passed nil object, returning nil proxy.");
        [self release];
        return nil;
    }
    
    // No super init for proxies.
    
    _object = object;
    _name = [name copy];
    _locked = YES;
    
    return self;
}
 
 
- (void)dealloc
{
    if (_locked)
    {
        NSLog(@"** ReleaseLockProxy (%@): deallocated while locked. This shouldn't happen, unless -dealloc is being called directly.", [self rlpObjectDescription]);
    }
    else
    {
        VerboseLog(@"-- ReleaseLockProxy (%@): deallocated while not locked.", [self rlpObjectDescription]);
    }
    
    [_object release];
    [_name release];
    
    [super dealloc];
}
 
 
- (void)rlpAllowRelease
{
    _locked = NO;
}
 
 
- (NSString *)rlpObjectDescription
{
    return _name ? _name : [_object description];
}
 
 
// *** Core functionality
 
- (void)release
{
    unsigned retainCount = [self retainCount];
    
    if (_locked && retainCount == 1)
    {
        // Breakpoint here to catch what would otherwise be the last release before crashing.
        NSLog(@"** ReleaseLockProxy (%@): released while locked and retain count is one - intercepting retain. Something is broken.", [self rlpObjectDescription]);
        return;
    }
    
    if (_locked)
    {
        VerboseLog(@"-- ReleaseLockProxy (%@): released while locked, but retain count > 1; retain count going from %u to %u.", [self rlpObjectDescription], retainCount, retainCount - 1);
    }
    else
    {
        VerboseLog(@"-- ReleaseLockProxy (%@): released while not locked; retain count going from %u to %u.", [self rlpObjectDescription], retainCount, retainCount - 1);
    }
    
    [super release];
}
 
 
- (id)autorelease
{
    VerboseLog(@"-- ReleaseLockProxy (%@): autoreleased while %slocked and retain count at %u.", [self rlpObjectDescription], _locked ? "" : "not ", [self retainCount]);
    return [super autorelease];
}
 
 
// *** Proxy stuff.
 
- (void)forwardInvocation:(NSInvocation *)invocation
{
    [invocation invokeWithTarget:_object];
}
 
 
- (NSMethodSignature *)methodSignatureForSelector:(SEL)selector
{
    NSMethodSignature       *result = nil;
    
    if (selector == @selector(initWithObject:name:) ||
        selector == @selector(initWithRetainedObject:name:) || 
        selector == @selector(rlpAllowRelease) ||
        selector == @selector(rlpObjectDescription))
    {
        result = [ReleaseLockProxy_SignatureTemplateClass methodSignatureForSelector:selector];
    }
    else
    {
        result = [(id)_object methodSignatureForSelector:selector];
    }
    
    return result;
}
 
 
+ (BOOL)instancesRespondToSelector:(SEL)selector
{
    if (selector == @selector(initWithObject:name:) ||
        selector == @selector(initWithRetainedObject:name:) || 
        selector == @selector(rlpAllowRelease) ||
        selector == @selector(rlpObjectDescription))
    {
        return YES;
    }
    else
    {
        return NO;
    }
}
 
 
- (BOOL)respondsToSelector:(SEL)selector
{
    return [ReleaseLockProxy instancesRespondToSelector:selector];
}
 
@end
 
 
@implementation ReleaseLockProxy_SignatureTemplateClass
 
+ (id)initWithObject:(id<NSObject>)object name:(NSString *)name  { return nil; }
+ (id)initWithRetainedObject:(id<NSObject>)object name:(NSString *)name  { return nil; }
+ (void)rlpAllowRelease  { }
+ (NSString *)rlpObjectDescription  { return nil; }
 
@end