//
//  NSEntityDescription+RKAdditions.h
//  RestKit
//
//  Created by Blake Watters on 3/22/12.
//  Copyright (c) 2009-2012 RestKit. All rights reserved.
//

#import <CoreData/CoreData.h>

/**
 The key for retrieving the name of the attribute that acts as
 the primary key from the user info dictionary of the receiving NSEntityDescription.

 **Value**: @"primaryKeyAttribute"
 */
extern NSString * const RKEntityDescriptionPrimaryKeyAttributeUserInfoKey;

/**
 The substitution variable used in predicateForPrimaryKeyAttribute.

 **Value**: @"PRIMARY_KEY_VALUE"
 @see predicateForPrimaryKeyAttribute
 */
extern NSString * const RKEntityDescriptionPrimaryKeyAttributeValuePredicateSubstitutionVariable;

/**
 Provides extensions to NSEntityDescription for various common tasks.
 */
@interface NSEntityDescription (RKAdditions)

/**
 The name of the attribute that acts as the primary key for the receiver.

 The primary key attribute can be configured in two ways:
    1. From within the Xcode Core Data editing view by
 adding the desired attribute's name as the value for the
 key `primaryKeyAttribute` to the user info dictionary.
    1. Programmatically, by retrieving the NSEntityDescription instance and
 setting the property's value.

 Programmatically configured values take precedence over the user info
 dictionary.
 */
@property (nonatomic, retain) NSString *primaryKeyAttribute;

/**
 Returns a cached predicate specifying that the primary key attribute is equal to the $PRIMARY_KEY_VALUE
 substitution variable.

 This predicate is cached to avoid parsing overhead during object mapping operations
 and must be evaluated using [NSPredicate predicateWithSubstitutionVariables:]

 @return A cached predicate specifying the value of the primary key attribute is equal to the $PRIMARY_KEY_VALUE
 substitution variable.
 */
- (NSPredicate *)predicateForPrimaryKeyAttribute;

/**
 Returns a predicate specifying that the value of the primary key attribute is equal to a given
 value. This predicate is constructed by evaluating the cached predicate returned by the
 predicateForPrimaryKeyAttribute with a dictionary of substitution variables specifying that
 $PRIMARY_KEY_VALUE is equal to the given value.

 @return A predicate speciying that the value of the primary key attribute is equal to a given value.
 */
- (NSPredicate *)predicateForPrimaryKeyAttributeWithValue:(id)value;

@end