Introduction to Restkit

by Peter Marks
http://petermarks.info

Restkit is a RESTful Object Mapping
Framework for iOS and OSX.

Server - Client

Web Application

Server - Client

Web Application

Database

Server - Client

Web Application

Database

RESTful JSON or XML
webservice

Server - Client

Web Application Obj C Application

Database

RESTful JSON or XML
webservice

Server - Client


Database Object graph

RESTful JSON or XML
webservice

Server - Client



RESTful JSON or XML
Restkit
webservice

Server - Client

GET Request


RESTful JSON or XML
Restkit
webservice

Server - Client

GET Request

POST Request
RESTful JSON or XML
Restkit
webservice

Two representations of the same data:

/contacts

/contacts

[{
    'contact': {
        'id': 1234,
        'full_name': 'Peter Marks',
        'email': 'petertmarks@gmail.com',
    }
},
{
        'id': 3456,
        'full_name': 'Barack Obama',
        'email': 'barack94@aol.com',
    }
}]

/contacts @interface Contact : RKObject {
NSNumber* _contactID;
NSString* _fullName;
NSString* _email;
[{ }
        'id': 1234, @property (retain) NSNumber* contactID;
@property (retain) NSString* fullName;
        'full_name': 'Peter Marks', @property (retain) NSString* email;
        'email': 'petertmarks@gmail.com', @end
    }
},
{
        'id': 3456,
        'full_name': 'Barack Obama',
        'email': 'barack94@aol.com',
    }
}]

/contacts @interface Contact : RKObject {
NSNumber* _contactID;
NSString* _fullName;
NSString* _email;
[{ }
        'id': 1234, @property (retain) NSNumber* contactID;
@property (retain) NSString* fullName;
        'full_name': 'Peter Marks', @property (retain) NSString* email;
        'email': 'petertmarks@gmail.com', @end
    }
}, @implementation Contact
@synthesize ...;
{
    'contact': { + (NSDictionary*)elementToPropertyMappings {
        'id': 3456, return [NSDictionary dictionaryWithKeysAndObjects:
@"id", @"contactID",
        'full_name': 'Barack Obama', @"full_name", @"fullName",
        'email': 'barack94@aol.com', @"email", @"email",
    } nil];
}] }

@end

Fetch objects from server

- (void)applicationDidFinishLaunching:(UIApplication*)application withOptions:(NSDictionary*)options {
RKClient* client = [RKClient clientWithBaseURL:@"http://restkit.org"];
}

- (void)loadContact {
RKObjectManager* manager = [RKObjectManager objectManagerWithBaseURL:@"http://restkit.org"];
[manager loadObjectsAtResourcePath:@"/contacts/1" objectClass:[Contact class] delegate:self]
}

- (void)objectLoader:(RKObjectLoader*)objectLoader didLoadObjects:(NSArray*)objects {
Contact* contact = [objects objectAtIndex:0];
NSLog(@"Loaded Contact ID #%@ -> Name: %@, Company: %@",
contact.id, contact.name, contact.company);
}

Set up routes

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
RKDynamicRouter* router = [RKDynamicRouter new];

// Define a default resource path for all unspecified HTTP verbs
[router routeClass:[Contact class] toResourcePath:@"/contacts/(contactID)"];
[router routeClass:[Contact class] toResourcePath:@"/contacts" forMethod:RKRequestMethodPOST];

[RKObjectManager sharedManager].router = router;
}

Post object to server

- (void) postObject {
Contact * newContact = [[Contact alloc] init];
newContact.fullName = @"Peter Marks";
newContact.email = @"petertmarks@gmail.com";
[[RKObjectManager sharedManager] postObject:newContact delegate:self];
}

contact.contactID, contact.fullName, contact.company);
}

Core Data
@interface Contact : RKManagedObject {}
@end

@implementation Contact
@synthesize ...;

+ (NSDictionary*)elementToPropertyMappings {
return [NSDictionary dictionaryWithKeysAndObjects:
@"id", @"contactID",
@"full_name", @"fullName",
@"email", @"email",
nil];
}

+ (NSString*)primaryKeyProperty {
return @"contactID";
}

@end

Relationship modeling
[{"project": {
    "id": 123,
    "name": "Produce RestKit Sample Code",
    "description": "We need more sample code!",
    "user": {
        "id": 1,
        "name": "Blake Watters",
        "email": "blake@twotoasters.com"
    },
    "tasks": [
        {"id": 1, "name": "Identify samples to write", "assigned_user_id": 1},
        {"id": 2, "name": "Write the code", "assigned_user_id": 1},
        {"id": 3, "name": "Push to Github", "assigned_user_id": 1},
        {"id": 4, "name": "Update the mailing list", "assigned_user_id": 1}
    ]
}},

Relationship mapping
@interface Project : RKManagedObject {
NSNumber* _projectID;
NSString* _name;
NSString* _description;
NSString* _userID;
User* _user;
NSArray* _tasks;
}

@property (nonatomic, retain) NSNumber* projectID;
@property (nonatomic, retain) NSString* name;
@property (nonatomic, retain) NSString* description;
@property (nonatomic, retain) NSString* userID;
@property (nonatomic, retain) User* user;
@property (nonatomic, retain) NSArray* tasks;

@end

Relationship mapping
@interface Project : RKManagedObject {
NSNumber* _projectID; @implementation Project
NSString* _name; @dynamic ...;
NSString* _description;
NSString* _userID; + (NSDictionary*)elementToPropertyMappings {...}
User* _user;
NSArray* _tasks; - (NSString*) primaryKeyProperty {
} return projectID;
}
@property (nonatomic, retain) NSNumber* projectID;
@property (nonatomic, retain) NSString* name; + (NSDictionary*)elementToRelationshipMappings {
@property (nonatomic, retain) NSString* description; return [NSDictionary dictionaryWithKeysAndObjects:
@property (nonatomic, retain) NSString* userID; @"user", @"user",
@property (nonatomic, retain) User* user; @"tasks", @"tasks",
@property (nonatomic, retain) NSArray* tasks; nil];
}
@end
+ (NSDictionary*)relationshipToPrimaryKeyPropertyMappings {
return [NSDictionary dictionaryWithObject:@"userID" forKey:@"user"];
}

@end

Relationship serialization

+ (NSArray*)relationshipsToSerialize {
return [NSArray arrayWithObject:@"tasks"];
}

[{"project": {
    "id": 123,
    "name": "Produce RestKit Sample Code",
    "description": "We need more sample code!",
    "tasks": [
        {"id": 1, "name": "Identify samples to write", "assigned_user_id": 1},
        {"id": 2, "name": "Write the code", "assigned_user_id": 1},
        {"id": 3, "name": "Push to Github", "assigned_user_id": 1},
        {"id": 4, "name": "Update the mailing list", "assigned_user_id": 1}
    ]
}},

Object mapping 2.0
Everything mentioned is for the current version of 0.9.2

Object mapping 2.0

Upcoming version 0.9.3 overhauls of Object mapping

Object mapping 2.0


Main difference is that mappings are no longer dependent
on class inheritance.

Object mapping 2.0


Main difference is that mappings are no longer dependent
on class inheritance.

// In this use-case Article is a vanilla NSObject with properties
RKObjectMapping* mapping = [RKObjectMapping mappingForClass:[Article class]];

// Add an attribute mapping to the object mapping directly
RKObjectAttributeMapping* titleMapping = [RKObjectAttributeMapping mappingFromKeyPath:@"title"
toKeyPath:@"title"];
[mapping addAttributeMapping:titleMapping];

RKRequestQueue
}

}

RKRequestQueue
}

}

// We have been obscured -- cancel any pending requests
- (void)viewWillDisappear:(BOOL)animated {
[[RKRequestQueue sharedQueue] cancelRequestsWithDelegate:self];
}

Background requests

- (void)backgroundUpload {
RKRequest* request = [[RKClient sharedClient] post:@"somewhere" delegate:self];
request.backgroundPolicy = RKRequestBackgroundPolicyNone; // Take no action with regard to backgrounding
request.backgroundPolicy = RKRequestBackgroundPolicyCancel; // If the app switches to the background, cancel the request
request.backgroundPolicy = RKRequestBackgroundPolicyContinue; // Continue the request in the background
request.backgroundPolicy = RKRequestBackgroundPolicyRequeue; // Cancel the request and place it back on the queue for next
activation
}

Multi-part requests

// Create an Attachment
RKParamsAttachment* attachment = [params setFile:myFilePath forParam:@"image1"];
attachment.MIMEType = @"image/gif";
attachment.fileName = @"picture.gif";

// Attach an Image from the App Bundle
UIImage* image = [UIImage imageNamed:@"another_image.png"];
NSData* imageData = UIImagePNGRepresentation(image);
[params setData:imageData MIMEType:@"image/png" forParam:@"image2"];

// Send a Request!
[[RKClient sharedClient] post:@"/uploadImages" params:params delegate:self];

Database seeding

RKManagedObjectSeeder* seeder = [RKManagedObjectSeeder objectSeederWithObjectManager:
[RKObjectManager sharedManager]];

// Seed the database with User objects. The class will be inferred via element registration
[seeder seedObjectsFromFiles:@"users.json", nil];

Integration Layers

Ruby on Rails
RKRailsRouter – A Router implementation aware of Ruby on Rails idioms

Three20
RKRequestTTModel – An implementation of the TTModel protocol for
Three20 that allows RestKit object loaders to drive Three20 tables

More information

• http://Restkit.org

• http://github.com/twotoasters/RestKit/

• http://groups.google.com/group/restkit

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