RFFeatureSupport.h

/*!
    RFFeatureSupport
    RFKit

    Copyright (c) 2012-2013, 2016, 2018 BB9z
    https://github.com/BB9z/RFKit

    The MIT License (MIT)
    http://www.opensource.org/licenses/mit-license.php
 */

#import <Availability.h>
#import <AvailabilityMacros.h>

#pragma mark -
/// These protocols are not real protocols, just a way to declare a class support something or not.

/// For RFUI components, storyboard was first class supported.
/// This protocol show a class not support init form nib. You must use init method to creat one.
#define RFNotSupportLoadFromNib             NSObject
#define RFOnlySupportLoadFromNib            NSObject

// 
#define RFForSubclass                       NSObject

/// All property support key value observing.
#define RFSupportKeyValueObserving          NSObject

#pragma mark -

// We purposefully don't have a matching @implementation.
// We don't want +asNonnull to ever actually be called
// because that will add a lot of overhead to every RF_NONNULL
// and we want RF_NONNULL to be very cheap.
// If there is no @implementation, then if the +asNonnull is
// actually called, we'll get a linker error complaining about
// the lack of @implementation.
@interface RF_NONNULL <__covariant Type>
// This as a class method so you don't need to
// declare an unused lvalue just for a __typeof
+ (Type _Nonnull)asNonnull;
@end

/**
 @define RF_AS_NONNULL(V)
 
 Converts an Objective-C object expression from _Nullable to _Nonnull.
 
 Crashes if it receives a nil! We must crash or else we'll receive static analyzer warnings when archiving. I think in Release mode, the compiler ignores the _Nonnull cast.
 
 @param V a _Nullable Objective-C object expression
 
 @ref https://gist.github.com/robb/d55b72d62d32deaee5fa
 */
#if defined(DEBUG) && !defined(NDEBUG)
#define RF_AS_NONNULL(V) \
({\
    __typeof__(V) __nullableV = V;\
    NSCAssert(__nullableV, @"Expected '%@' not to be nil.", @#V);\
    (__typeof([RF_NONNULL<__typeof(V)> asNonnull]))__nullableV;\
})
#else
#define RF_AS_NONNULL(V) \
    (__typeof([RF_NONNULL<__typeof(V)> asNonnull]))V
#endif