RestKit: Post and Return Results

Posted on Tuesday, July 24th, 2012 under iOS, Rails

I’ve spent the last couple of weeks getting to know RestKit. We’re using it for some new internal projects including building the new Spots iOS App on it.

Something that I found interesting and with little documentation online is how to POST an object to a server over JSON but also to easily retain the results that are sent back. Here’s how:

Overview

In this example we’re going to be working with a User object which has two characteristics.

• ID
• Device ID

Nothing crazy, all nice and simple. We’re going to check if the Device ID already exists within the users table. If not, we’ll create it whilst retaining the newly created ID.

User Object

User.h

#import Foundation/Foundation.h

@interface User : NSObject

@property (nonatomic, retain) NSNumber* identifier;
@property (nonatomic, retain) NSString *device_id;

@end

User.m

#import "User.h"

@implementation User

@synthesize device_id, identifier;

@end

Posting and Returning

I’ve already created an NSDictionary which contains all live User IDs and Device IDs call userList. I then check against the userList dictionary to see if the Device Id exists. If it doesn’t, create it and assign the newly created ID to currentUser.identifier:

if ([[usersList allKeys] containsObject:device_id) {
    NSLog(@"User exists");

    currentUser.identifier = [usersList objectForKey: device_id];
    currentUser.device_id = device_id;
} else {
    NSLog(@"Nope, never seen it");

    RKObjectRouter *router = [RKObjectManager sharedManager].router;
    [router routeClass:[User class] toResourcePath:@"/users.json" forMethod:RKRequestMethodPOST];

    RKObjectMapping *userMapping = [RKObjectMapping mappingForClass:[User class]];
    [userMapping mapKeyPath:@"device_id" toAttribute:@"device_id"];
    [userMapping mapKeyPath:@"id" toAttribute:@"identifier"];

    [[RKObjectManager sharedManager].mappingProvider registerMapping:userMapping withRootKeyPath:@"user"];
    currentUser.device_id = device_id;

    [[RKObjectManager sharedManager] postObject:currentUser usingBlock:^(RKObjectLoader *loader){
        loader.onDidLoadObject = ^(id obj) {
            NSLog(@"UserID: %@", currentUser.identifier);
        };
    }];
}