//
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// RACSubscriptingAssignmentTrampoline.h
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// ReactiveCocoa
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//
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// Created by Josh Abernathy on 9/24/12.
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// Copyright (c) 2012 GitHub, Inc. All rights reserved.
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//
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#import <Foundation/Foundation.h>
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#import "RACEXTKeyPathCoding.h"
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@class RACSignal;
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/// Assigns a signal to an object property, automatically setting the given key
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/// path on every `next`. When the signal completes, the binding is automatically
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/// disposed of.
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///
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/// There are two different versions of this macro:
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///
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/// - RAC(TARGET, KEYPATH, NILVALUE) will bind the `KEYPATH` of `TARGET` to the
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/// given signal. If the signal ever sends a `nil` value, the property will be
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/// set to `NILVALUE` instead. `NILVALUE` may itself be `nil` for object
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/// properties, but an NSValue should be used for primitive properties, to
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/// avoid an exception if `nil` is sent (which might occur if an intermediate
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/// object is set to `nil`).
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/// - RAC(TARGET, KEYPATH) is the same as the above, but `NILVALUE` defaults to
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/// `nil`.
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///
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/// See -[RACSignal setKeyPath:onObject:nilValue:] for more information about the
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/// binding's semantics.
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///
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/// Examples
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///
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/// RAC(self, objectProperty) = objectSignal;
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/// RAC(self, stringProperty, @"foobar") = stringSignal;
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/// RAC(self, integerProperty, @42) = integerSignal;
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///
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/// WARNING: Under certain conditions, use of this macro can be thread-unsafe.
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/// See the documentation of -setKeyPath:onObject:nilValue:.
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#define RAC(TARGET, ...) \
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metamacro_if_eq(1, metamacro_argcount(__VA_ARGS__)) \
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(RAC_(TARGET, __VA_ARGS__, nil)) \
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(RAC_(TARGET, __VA_ARGS__))
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/// Do not use this directly. Use the RAC macro above.
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#define RAC_(TARGET, KEYPATH, NILVALUE) \
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[[RACSubscriptingAssignmentTrampoline alloc] initWithTarget:(TARGET) nilValue:(NILVALUE)][@keypath(TARGET, KEYPATH)]
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@interface RACSubscriptingAssignmentTrampoline : NSObject
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- (id)initWithTarget:(id)target nilValue:(id)nilValue;
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- (void)setObject:(RACSignal *)signal forKeyedSubscript:(NSString *)keyPath;
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@end
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