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//
// GTMTypeCasting.h
//
// Copyright 2010 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy
// of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
//
#import <Foundation/Foundation.h>
#import "GTMDefines.h"
// These are some basic macros for making down-casting safer in Objective C.
// They are loosely based on the same cast types with similar names in C++.
// A typical usage would look like this:
//
// Bar* b = [[Bar alloc] init];
// Foo* a = GTM_STATIC_CAST(Foo, b);
//
// Note that it's GTM_STATIC_CAST(Foo, b) and not GTM_STATIC_CAST(Foo*, b).
//
// GTM_STATIC_CAST runs only in debug mode, and will assert if and only if:
// - object is non nil
// - [object isKindOfClass:[cls class]] returns nil
//
// otherwise it returns object.
//
// GTM_DYNAMIC_CAST runs in both debug and release and will return nil if
// - object is nil
// - [object isKindOfClass:[cls class]] returns nil
//
// otherwise it returns object.
//
// Support functions for dealing with casting.
GTM_INLINE id GTMDynamicCastSupport(Class cls, id object) {
_GTMDevAssert(cls, @"Nil Class");
return [object isKindOfClass:cls] ? object : nil;
}
GTM_INLINE id GTMStaticCastSupport(Class cls, id object) {
id value = nil;
if (object) {
value = GTMDynamicCastSupport(cls, object);
_GTMDevAssert(value, @"Could not cast %@ to class %@", object, cls);
}
return value;
}
#ifndef GTM_STATIC_CAST
#ifdef DEBUG
#define GTM_STATIC_CAST(type, object) \
((type *) GTMStaticCastSupport([type class], object))
#else
#define GTM_STATIC_CAST(type, object) ((type *) (object))
#endif
#endif
#ifndef GTM_DYNAMIC_CAST
#define GTM_DYNAMIC_CAST(type, object) \
((type *) GTMDynamicCastSupport([type class], object))
#endif
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