Instantiating Custom Class from NSDictionary

Question

I have a feeling that this is stupid question, but I\'ll ask anyway...

I have a collection of NSDictionary objects whose key/value pairs correspond to a cus

Answer 1

Just add category for NSObject for getting dictionaryRepresentation from your custom objects (in my case using in JSON serialization only):

//  NSObject+JSONSerialize.h
#import 

@interface NSObject(JSONSerialize)

- (NSDictionary *)dictionaryRepresentation;

@end

//  NSObject+JSONSerialize.m
#import "NSObject+JSONSerialize.h"
#import 

@implementation NSObject(JSONSerialize)

+ (instancetype)instanceWithDictionary:(NSDictionary *)aDictionary {
    return [[self alloc] initWithDictionary:aDictionary];
}

- (instancetype)initWithDictionary:(NSDictionary *)aDictionary {
    aDictionary = [aDictionary clean];

    self.isReady = NO;

    for (NSString* propName in [self allPropertyNames]) {
        [self setValue:aDictionary[propName] forKey:propName];
    }

    //You can add there some custom properties with wrong names like "id"
    //[self setValue:aDictionary[@"id"] forKeyPath:@"objectID"];
    self.isReady = YES;

    return self;
}

- (NSDictionary *)dictionaryRepresentation {
    NSMutableDictionary *result = [NSMutableDictionary dictionary];
    NSArray *propertyNames = [self allPropertyNames];

    id object;
    for (NSString *key in propertyNames) {
        object = [self valueForKey:key];
        if (object) {
            [result setObject:object forKey:key];
        }
    }

    return result;
}

- (NSArray *)allPropertyNames {
    unsigned count;
    objc_property_t *properties = class_copyPropertyList([self class], &count);

    NSMutableArray *rv = [NSMutableArray array];

    unsigned i;
    for (i = 0; i < count; i++) {
        objc_property_t property = properties[i];
        NSString *name = [NSString stringWithUTF8String:property_getName(property)];
        [rv addObject:name];
    }
    //You can add there some custom properties with wrong names like "id"
    //[rv addObject:@"objectID"];
    //Example use inside initWithDictionary:
    //[self setValue:aDictionary[@"id"] forKeyPath:@"objectID"];

    free(properties);

    return rv;
}

@end

Also, you can see that my solution will not work with custom objects with nested objects or arrays. For Arrays - just change the lines of code in dictionaryRepresentation method:

    if (object) {
        if ([object isKindOfClass:[NSArray class]]) {
            @autoreleasepool {
                NSMutableArray *array = [NSMutableArray array];
                for (id item in (NSArray *)object) {
                    [array addObject:[item dictionaryRepresentation]];
                }

                [result setObject:array forKey:key];
            }
        } else {
            [result setObject:object forKey:key];
        }
    }