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KDNullSafe.m
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KDNullSafe.m
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//
// NullSafe.m
//
// Version 1.2
//
// Created by Nick Lockwood on 19/12/2012.
// Copyright 2012 Charcoal Design
//
// Distributed under the permissive zlib License
// Get the latest version from here:
//
// https://github.com/nicklockwood/NullSafe
//
// This software is provided 'as-is', without any express or implied
// warranty. In no event will the authors be held liable for any damages
// arising from the use of this software.
//
// Permission is granted to anyone to use this software for any purpose,
// including commercial applications, and to alter it and redistribute it
// freely, subject to the following restrictions:
//
// 1. The origin of this software must not be misrepresented; you must not
// claim that you wrote the original software. If you use this software
// in a product, an acknowledgment in the product documentation would be
// appreciated but is not required.
//
// 2. Altered source versions must be plainly marked as such, and must not be
// misrepresented as being the original software.
//
// 3. This notice may not be removed or altered from any source distribution.
//
#import "KDNullSafe.h"
#import <objc/runtime.h>
#import "KDLogger.h"
@implementation NSNull (NullSafe)
#if KDNULLSAFE_ENABLED
- (NSMethodSignature *)methodSignatureForSelector:(SEL)selector
{
@synchronized([self class])
{
//look up method signature
NSMethodSignature *signature = [super methodSignatureForSelector:selector];
if (!signature)
{
//not supported by NSNull, search other classes
static NSMutableSet *classList = nil;
static NSMutableDictionary *signatureCache = nil;
if (signatureCache == nil)
{
classList = [[NSMutableSet alloc] init];
signatureCache = [[NSMutableDictionary alloc] init];
//get class list
int numClasses = objc_getClassList(NULL, 0);
Class *classes = (Class *)malloc(sizeof(Class) * numClasses);
numClasses = objc_getClassList(classes, numClasses);
//add to list for checking
NSMutableSet *excluded = [NSMutableSet set];
for (int i = 0; i < numClasses; i++)
{
//determine if class has a superclass
BOOL isNSObject = NO;
Class class = classes[i];
Class superClass = class_getSuperclass(class);
while (superClass)
{
if (superClass == [NSObject class])
{
isNSObject = YES;
break;
}
Class next = class_getSuperclass(superClass);
if (next) [excluded addObject:superClass];
superClass = next;
}
//only include NSObject subclasses
if (isNSObject)
{
[classList addObject:class];
}
}
//remove all classes that have subclasses
for (Class class in excluded)
{
[classList removeObject:class];
}
//free class list
free(classes);
}
//check implementation cache first
NSString *selectorString = NSStringFromSelector(selector);
signature = signatureCache[selectorString];
if (!signature)
{
//find implementation
for (Class class in classList)
{
if ([class instancesRespondToSelector:selector])
{
signature = [class instanceMethodSignatureForSelector:selector];
break;
}
}
//cache for next time
signatureCache[selectorString] = signature ?: [NSNull null];
}
else if ([signature isKindOfClass:[NSNull class]])
{
signature = nil;
}
}
return signature;
}
}
- (void)forwardInvocation:(NSInvocation *)invocation {
KDClassLog(@"WARNING! NSNull receive unknown invocation.");
[invocation invokeWithTarget:nil];
}
#endif
@end