JSONMappableObject

Example.md

A basic class for mapping JSON objects to their models. Also fully compliant w/ NSCoding automatically. The only thing you need to do is subclass the model, declare your properties, and then override mapping using the following syntax:

- (NSMutableDictionary *)mapping {
  NSMutableDictionary *mapping = [super mapping];
  mapping[@"propertyName"] = @"associatedJSONKey";
}

If your property maps to another JSONMappableObject, or an array of them, use the following syntax for your mapping key:

@``<#propertyName#>``:``<#ClassName#>

- (NSMutableDictionary *)mapping {
  NSMutableDictionary *mapping = [super mapping];
  mapping[@"@propertyName:TypeOfClass"] = @"associatedJSONKey";
}

In the future, I will add the introspection necessary to get the class type and avoid having to change this, but for now, just specify the class.

###Example

GIGitHubIssue.h

#import "JSONMappableObject.h"

@class GIGitHubUser;
@class GIGitHubIssueMilestone;
@class GIGitHubPartialPullRequest;

@interface GIGitHubIssue : JSONMappableObject
@property (nonatomic) NSInteger identifier;
@property (copy, nonatomic) NSString *apiURL;
@property (copy, nonatomic) NSString *htmlURL;
@property (nonatomic) NSInteger number;
@property (copy, nonatomic) NSString *state;
@property (copy, nonatomic) NSString *title;
@property (copy, nonatomic) NSString *bodyMarkdown;
@property (strong, nonatomic) GIGitHubUser *user;
@property (strong, nonatomic) NSArray *labels; // GIGitHubIssueLabel
@property (strong, nonatomic) GIGitHubUser *assignee;
@property (strong, nonatomic) GIGitHubIssueMilestone *milestone;
@property (strong, nonatomic) GIGitHubPartialPullRequest *pullRequest;
@property (nonatomic) NSInteger commentCount;
@property (copy, nonatomic) NSString *closedAt;
@property (copy, nonatomic) NSString *createdAt;
@property (copy, nonatomic) NSString *updatedAt;
@property (nonatomic) BOOL locked;
@end

GIGitHubIssue.m

#import "GIGitHubIssue.h"

@implementation GIGitHubIssue
- (NSMutableDictionary *)mapping {
    NSMutableDictionary *mapping = [super mapping];
    mapping[@"identifier"] = @"id";
    mapping[@"apiURL"] = @"url";
    mapping[@"htmlURL"] = @"html_url";
    mapping[@"number"] = @"number";
    mapping[@"state"] = @"state";
    mapping[@"title"] = @"title";
    mapping[@"bodyMarkdown"] = @"body";
    mapping[@"@user:GIGitHubUser"] = @"user";
    mapping[@"@labels:GIGitHubIssueLabel"] = @"labels";
    mapping[@"@assignee:GIGitHubUser"] = @"assignee";
    mapping[@"@milestone:GIGitHubIssueMilestone"] = @"milestone";
    mapping[@"commentCount"] = @"comments";
    mapping[@"@pullRequest:GIGitHubPartialPullRequest"] = @"pull_request";
    mapping[@"closedAt"] = @"closed_at";
    mapping[@"createdAt"] = @"created_at";
    mapping[@"updatedAt"] = @"updated_at";
    mapping[@"locked"] = @"locked";
    return mapping;
}
@end

JSONMappableObject.h

//
//  Created by Logan Wright on 1/24/15.
//  Copyright (c) 2015 LowriDevs. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface JSONMappableObject : NSObject <NSCoding>
- (NSMutableDictionary *)mapping;
- (instancetype)initWithJSONRepresentation:(NSDictionary *)jsonRepresentation;
@end

JSONMappableObject.m

//
//  JSONObject.m
//  GitIssues-iOS
//
//  Created by Logan Wright on 1/24/15.
//  Copyright (c) 2015 LowriDevs. All rights reserved.
//

#import "JSONMappableObject.h"
#import <objc/objc-runtime.h>

@implementation JSONMappableObject
- (NSMutableDictionary *)mapping {
    return [NSMutableDictionary dictionary];
}
- (instancetype)init {
    @throw [NSException exceptionWithName:NSInternalInconsistencyException
                                   reason:@"-init is not a valid initializer for a JSONObject class."
                                 userInfo:nil];
    return nil;
}
- (instancetype)initWithJSONRepresentation:(NSDictionary *)jsonRepresentation {
    self = [super init];
    if (self) {
        NSDictionary *mapping = [self mapping];
        for (__strong NSString *propertyName in mapping.allKeys) {
            NSString *associatedJSONKey = mapping[propertyName];
            id associatedValue = jsonRepresentation[associatedJSONKey];
            
            if ([propertyName hasPrefix:@"@"]) { // Use prefix to indicate another JSONObject
                propertyName = [propertyName substringFromIndex:1];
                NSArray *components = [propertyName componentsSeparatedByString:@":"];
                
                NSString *assertionMessage = @"Declaring a property as a subclass of JSONMappableObject requires the following syntax '@propertyName:ClassName'";
                
                NSAssert(components.count == 2, assertionMessage);
                
                propertyName = components.firstObject;
                NSString *className = components.lastObject;
                Class propertyClass = NSClassFromString(className);
                
                if (!associatedValue || [associatedValue isKindOfClass:[NSNull class]]) {
                    [self setValue:nil forKey:propertyName];
                } else if ([associatedValue isKindOfClass:[NSArray class]]) {
                    NSMutableArray *objects = [NSMutableArray array];
                    for (id ob in (NSArray *)associatedValue) {
                        JSONMappableObject *mappedOb = [[propertyClass alloc] initWithJSONRepresentation:ob];
                        [objects addObject:mappedOb];
                    }
                    [self setValue:objects forKey:propertyName];
                } else {
                    JSONMappableObject *jsonObject = [[propertyClass alloc] initWithJSONRepresentation:associatedValue];
                    [self setValue:jsonObject forKey:propertyName];
                }
            } else {
                if (!associatedValue || [associatedValue isKindOfClass:[NSNull class]]) {
                    [self setValue:nil forKey:propertyName];
                    continue;
                }
                [self setValue:associatedValue forKey:propertyName];
            }

        }
        
    }
    return self;
}

#pragma mark - NSCoding

- (instancetype)initWithCoder:(NSCoder *)aDecoder {
    self = [super init];
    if (self) {
        for (NSString *property in [self properties]) {
            [self setValue:[aDecoder decodeObjectForKey:property] forKey:property];
        }
    }
    return self;
}

- (void)encodeWithCoder:(NSCoder *)aCoder {
    for (NSString *property in [self properties]) {
        [aCoder encodeObject:[self valueForKey:property] forKey:property];
    }
}

- (NSArray *)properties {
    unsigned count;
    objc_property_t *properties = class_copyPropertyList([self class], &count);
    NSMutableArray *propertyNames = [NSMutableArray array];
    for (int i = 0; i < count; i++) {
        objc_property_t property = properties[i];
        const char * name = property_getName(property);
        NSString *stringName = [NSString stringWithUTF8String:name];
        [propertyNames addObject:stringName];
    }
    free(properties);
    return propertyNames;
}

@end