Objective-C isEqual implementation for Parse objects (PFObject, PFFile, and PFRelation)

PFObject+YSComparison.h

//
//  PFObject+YSComparison.h
//
//  Created by Ed McManus for Yardsale Inc. on 2/1/13
//  Learn more at https://getyardsale.com
//
//  Requires BlocksKit https://github.com/pandamonia/BlocksKit
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the Software is
//  furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in
//  all copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
//  THE SOFTWARE.
//

#import <Parse/Parse.h>

@interface PFObject (YSComparison)
- (NSDictionary*)ys_dictionaryRepresentation;
- (BOOL)ys_isEqual:(id)object;
@end

@interface PFFile (YSComparison)
- (BOOL)ys_isEqual:(id)object;
@end

@interface PFRelation (YSComparison)
- (BOOL)ys_isEqual:(id)object;
@end

PFObject+YSComparison.m

//
//  PFObject+YSComparison.m
//
//  Created by Ed McManus for Yardsale Inc. on 2/1/13
//  Learn more at https://getyardsale.com
//
//  Requires BlocksKit https://github.com/pandamonia/BlocksKit
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the Software is
//  furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in
//  all copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
//  THE SOFTWARE.
//

#import "PFObject+YSComparison.h"

static bool compareBySelectors(SEL selectors[], NSObject* object1, NSObject* object2);

#pragma mark - PFFile

@implementation PFFile (YSComparison)
- (BOOL)ys_isEqual:(id)object
{
    if ([self isKindOfClass:[object class]])
    {
        // Skip getData check if it requires a request
        if (![self isDataAvailable] || ![object isDataAvailable])
        {
            SEL selectors[] = { @selector(url), @selector(name), @selector(isDataAvailable), };
            return compareBySelectors( selectors, self, object );
        }
        else
        {
            SEL selectors[] = { @selector(url), @selector(name), @selector(isDataAvailable), @selector(getData), };
            return compareBySelectors( selectors, self, object );
        }
    }
    return NO;
}
@end

#pragma mark - PFRelation

@implementation PFRelation (YSComparison)
- (BOOL)ys_isEqual:(id)object
{
    if ([object isKindOfClass:[self class]])
    {
        SEL selectors[] = {
            @selector(parent),
            @selector(key),
            @selector(targetClass),
        };
        return compareBySelectors(selectors, self, object);
    }
    return NO;
}
@end

#pragma mark - PFObject

@implementation PFObject (YSComparison)
- (NSDictionary*)ys_dictionaryRepresentation
{
    NSArray * keys = [self allKeys];
    NSArray * values = [keys map:^id(NSString *key) {
        return self[key];
    }];
    return [NSDictionary dictionaryWithObjects:values forKeys:keys];
}

- (BOOL)ys_isEqual:(id)object
{
    if ([object isKindOfClass:[self class]])
    {
        SEL selectors[] = {
            @selector(objectId),
            @selector(createdAt),
            @selector(updatedAt),
            @selector(className),
            @selector(ys_dictionaryRepresentation),
        };
        return compareBySelectors(selectors, self, object);
    }
    return NO;
}
@end

#pragma mark -

/*
 * Compare two objects using a C-style array of selectors.
 */
static bool compareBySelectors(SEL selectors[], NSObject* object1, NSObject* object2)
{
    int selectorTypeSize = sizeof(SEL);
    int selectorArraySize = sizeof(*selectors);
    int selectorCount = selectorArraySize / selectorTypeSize;
    for (int i=0; i<selectorCount; i++)
    {
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
        SEL selector = selectors[i];
        id value1 = [object1 performSelector:selector];
        id value2 = [object2 performSelector:selector];
#pragma clang diagnostic pop
        
        BOOL equal;
        if ([value1 respondsToSelector:@selector(ys_isEqual:)] && [value2 respondsToSelector:@selector(ys_isEqual:)])
        {
            equal = ((value1 == value2) || [value1 ys_isEqual:value2]);
        }
        else
        {
            equal = ((value1 == value2) || [value1 isEqual:value2]);
        }
        
        if (!equal)
        {
            return NO;
        }
    }
    return YES;
}