Nil, nil, NULL, NSNull, kCFNull

Nil nil, NULL, NSNull, kCFNull difference

• Nil Objective-C instance object pointer null: NSSring * STR = nil;

#define nil ((void*)0)
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• Nil: Class Class = Nil;

#define nil ((void*)0)
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• Char *p = NULL;

#define NULL ((void*)0)
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• NSNull is an Objective-C class that inherits NSObject, mostly used for null values in array dictionaries

@interface NSNull : NSObject <NSCopying, NSSecureCoding>
+ (NSNull *)null;
@end
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• KCFNull is a singleton of NSNull [NSNull null]

typedef const struct CF_BRIDGED_TYPE(NSNull) __CFNull * CFNullRef;
const CFNullRef kCFNull;    // the singleton null instance
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