//
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// EXTKeyPathCoding.h
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// extobjc
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//
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// Created by Justin Spahr-Summers on 19.06.12.
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// Copyright (C) 2012 Justin Spahr-Summers.
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// Released under the MIT license.
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//
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#import <Foundation/Foundation.h>
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#import "RACmetamacros.h"
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/**
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* \@keypath allows compile-time verification of key paths. Given a real object
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* receiver and key path:
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*
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* @code
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NSString *UTF8StringPath = @keypath(str.lowercaseString.UTF8String);
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// => @"lowercaseString.UTF8String"
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NSString *versionPath = @keypath(NSObject, version);
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// => @"version"
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NSString *lowercaseStringPath = @keypath(NSString.new, lowercaseString);
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// => @"lowercaseString"
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* @endcode
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*
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* ... the macro returns an \c NSString containing all but the first path
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* component or argument (e.g., @"lowercaseString.UTF8String", @"version").
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*
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* In addition to simply creating a key path, this macro ensures that the key
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* path is valid at compile-time (causing a syntax error if not), and supports
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* refactoring, such that changing the name of the property will also update any
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* uses of \@keypath.
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*/
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#define keypath(...) \
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metamacro_if_eq(1, metamacro_argcount(__VA_ARGS__))(keypath1(__VA_ARGS__))(keypath2(__VA_ARGS__))
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#define keypath1(PATH) \
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(((void)(NO && ((void)PATH, NO)), strchr(# PATH, '.') + 1))
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#define keypath2(OBJ, PATH) \
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(((void)(NO && ((void)OBJ.PATH, NO)), # PATH))
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/**
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* \@collectionKeypath allows compile-time verification of key paths across collections NSArray/NSSet etc. Given a real object
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* receiver, collection object receiver and related keypaths:
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*
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* @code
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NSString *employessFirstNamePath = @collectionKeypath(department.employees, Employee.new, firstName)
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// => @"employees.firstName"
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NSString *employessFirstNamePath = @collectionKeypath(Department.new, employees, Employee.new, firstName)
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// => @"employees.firstName"
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* @endcode
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*
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*/
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#define collectionKeypath(...) \
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metamacro_if_eq(3, metamacro_argcount(__VA_ARGS__))(collectionKeypath3(__VA_ARGS__))(collectionKeypath4(__VA_ARGS__))
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#define collectionKeypath3(PATH, COLLECTION_OBJECT, COLLECTION_PATH) ([[NSString stringWithFormat:@"%s.%s",keypath(PATH), keypath(COLLECTION_OBJECT, COLLECTION_PATH)] UTF8String])
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#define collectionKeypath4(OBJ, PATH, COLLECTION_OBJECT, COLLECTION_PATH) ([[NSString stringWithFormat:@"%s.%s",keypath(OBJ, PATH), keypath(COLLECTION_OBJECT, COLLECTION_PATH)] UTF8String])
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