2020-02-27 00:02:03 +04:00

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//
// ASWeakProxy.mm
// Texture
//
// Copyright (c) Facebook, Inc. and its affiliates. All rights reserved.
// Changes after 4/13/2017 are: Copyright (c) Pinterest, Inc. All rights reserved.
// Licensed under Apache 2.0: http://www.apache.org/licenses/LICENSE-2.0
//
#import "ASWeakProxy.h"
#import <AsyncDisplayKit/ASObjectDescriptionHelpers.h>
#import <AsyncDisplayKit/ASAssert.h>
@implementation ASWeakProxy
- (instancetype)initWithTarget:(id)target
{
if (self) {
_target = target;
}
return self;
}
+ (instancetype)weakProxyWithTarget:(id)target NS_RETURNS_RETAINED
{
return [[ASWeakProxy alloc] initWithTarget:target];
}
- (id)forwardingTargetForSelector:(SEL)aSelector
{
return _target;
}
- (BOOL)respondsToSelector:(SEL)aSelector
{
return [_target respondsToSelector:aSelector];
}
- (BOOL)conformsToProtocol:(Protocol *)aProtocol
{
return [_target conformsToProtocol:aProtocol];
}
/// Strangely, this method doesn't get forwarded by ObjC.
- (BOOL)isKindOfClass:(Class)aClass
{
return [_target isKindOfClass:aClass];
}
- (NSString *)description
{
return ASObjectDescriptionMake(self, @[@{ @"target": _target ?: (id)kCFNull }]);
}
- (NSMethodSignature *)methodSignatureForSelector:(SEL)sel
{
ASDisplayNodeAssertNil(_target, @"ASWeakProxy got %@ when its target is still alive, which is unexpected.", NSStringFromSelector(_cmd));
// Unfortunately, in order to get this object to work properly, the use of a method which creates an NSMethodSignature
// from a C string. -methodSignatureForSelector is called when a compiled definition for the selector cannot be found.
// This is the place where we have to create our own dud NSMethodSignature. This is necessary because if this method
// returns nil, a selector not found exception is raised. The string argument to -signatureWithObjCTypes: outlines
// the return type and arguments to the message. To return a dud NSMethodSignature, pretty much any signature will
// suffice. Since the -forwardInvocation call will do nothing if the target does not respond to the selector,
// the dud NSMethodSignature simply gets us around the exception.
return [NSMethodSignature signatureWithObjCTypes:"@^v^c"];
}
- (void)forwardInvocation:(NSInvocation *)invocation
{
ASDisplayNodeAssertNil(_target, @"ASWeakProxy got %@ when its target is still alive, which is unexpected.", NSStringFromSelector(_cmd));
}
@end