Dreamfreeze Software

Now that I've been working with the iPad for a few weeks, I really like what Apple has done with the development process. 

Making Hybrid iPhone/iPad applications is very easy for existing iPhone apps. You simply open up the xib in IB and select the File -> Create iPad version menu option. That combined with UI_USER_INTERFACE_IDIOM() and you can reuse all your existing view controllers while having full control over how you handle specific devices. 

I think there merit in making hybrid apps from existing iPhone apps in many cases. Nibipedia for instance is a perfect candidate for this. It is a small lightweight app that is mostly UIWebView driven. There isn't a lot of UI code for animations or dynamic view creation. It makes sense to just create a hybrid app.

Hansel on the other hand is more complicated. My initial attempt to make a hybrid app has failed miserably. The main problem is that I have lots of UI code that moves views around and makes assumptions about the device, that it is indeed an iPhone. While I could have written it in a more generic fashion, I never felt the need to do so. It didn't seem like there was enough benefit for spending the extra time on a free app. 

The thing with UI animation code is that it tends to not be as reusable. Some of the code I am able to reuse via clipboard inheritance. However, I created those effects specifically for Hansel and not with the intention of reusing them or for that matter with the intent of supporting the iPad or any other device. I will end up creating separate iPad view controllers for Hansel, if and when I get around to porting it. There really isn't a big need for me to do so. I created Hansel as a free app so I could easily show my iPhone app development skills. It was created to be a simple application and it will probably stay that way on the iPhone only. 

Back to the topic at hand. Creating Contacts Map was a great experience. It is meant to be an iPad only app. While it could be done on the iPhone pretty easily, the iPad is perfect for this app (or maybe this app is perfect for the iPad...). Again, I am doing this work to show that I can do iPad development and that I am capable with both the SDK and web service consumption. It will be up in the app store soon, I just have to find an icon for it and I'll be good to go.

I have a good concept for my next application involving the iPad, which will also have a Mac component. It centers around remote control of the Mac for machines setup as media centers. More on that next time.

I started a new job over the new year. Working for ITR Group was a good experience but they lacked direction and leadership. I was the senior most engineer out of a team of 6. It was enjoyable but I'm glad it is over. I have iPhone work I'm doing on the side, so I still get my fix.

Back at McKesson, I am now working with GWT, Java, and RDF. It is interesting work and I am happy to broaden my skill set. I forgot how challenging working with Eclipse can be, but I plan to work with CXF web services to expose data to the iPhone. I'll be writing a set of articles about that in the coming months.

This is the fourth installment about using and accessing RESTful webservices on the iPhone.

You can download the example project artifacts here. This includes the iPhone example project and SQL Server scripts for generating the CarDealer DB and demo data.

Getting Started with iPhone + Data Services

Getting this post out took much longer than I thought. Setting up my .NET development and hosting environment was painful. My personal environment is different from my work environment, so I had some catch up after several months of not using it. 

Setting up SQL Server Express was not bad at all. I had an older version and decided to upgrade it to '08. Trying to create the data services project was painless as well. The pain began when I tried deploying to IIS 6 locally. While I'm sure someone out there can do it, I was unable to make it work. I decided to setup a Windows Server '08 VM to ease the pain. It helped a lot, but was very time consuming.

I started looking around for a free .NET hosting service that I could use to make the services public for the example. After several hours a gave up on this. I could have paid for a cheap one, but I doubt that I'd ever use it for anything else. 

I then took some cycles and looked at using Azure. I do not have Vista (XP ftw) for my dev environment and could not install the SDK required for deployment. I was able to setup an Azure SQL database and import all of my example tables, but without being able to deploy the data services from the cloud it was useless. 

Please note that my indication of wanting to use Azure for this example is not representative of my being a cloud advocate. Cloud computing, like most other technologies, has its uses in certain circumstances but it is not and will never be a silver bullet.

Setting up the backend

I finally decided that I would just make the database scripts available and point people to this article on creating data services. If you have the prerequisites below, then it should take less than half an hour to be up and running. I suggest naming it CarDealer.svc. I apologize for not supplying the source, but I don't want to have to muck around with cleaning out my connection strings and such. It is fairly easy and you will probably need to setup new data services in the future, so why not get some practice.

In order to setup the necessary backend you will need VS '08 SP1 [or later], SQL Server Express '08 [any version may work], and IIS 7.0. The key is deploying the data service is a way that is visible to the iPhone/Simulator. If you cannot load the CarDealer.svc in a browser on the client platform then you will not be able to use the data service in the iPhone example.

To make the iPhone example work with your services, modify the kServicesURL constant found in CarDealerAppDelegate. It should point to the fully qualified URL of your deployed CarDealer.svc.

Car Dealer

The Example

Once you have everything running, and configured to point to your shiny new services, you will be presented with the screen on the right. It is a simple UI that displays a list of people in the system. Selecting a person will reveal their cars. Picking a car will show its maintenance records. Like all my examples in this series, this one is plain, out-of-the-box, and meant to be a technology demonstration. Don't submit these to the app store and expect to win a design award.

The Code

RestConnection has been updated in this example. The BSJSONAdditions have also been brought into the project, but are unchanged in this example.

I'm going to talk about the interesting code below. I will not go into the mundane details of UINavigationController et al. You can find more info on that here.

RestConnection

There are a couple of modifications to RestConnection. 

Data Services has a couple of nuances. First, it always wraps its responses in a root object, "d". Second, a data service can expose resources that are either singular or plural. If a solitary resource is specified by a URL, then the root object will contain a single object [dictionary]. If the resource specifies a group of objects, then the root object will contain an array. 

It is up to the client to understand which will be returned. In order to better support this behavior, RestConnection has been extended to A) "unwrap" the data for us and B) provide an additional method, - (NSArray *)arrayData, for handling collections.

Person

The person view controller is meant to display all the people in the system. For a production environment this would have to be retooled so it supported paging and allowed for searching. That is out of the scope of this example but there will be a post about both concepts later.

In the viewDidLoad method, a RestConnection is setup for use by the screen. kServicesURL defines the absolute path to the .svc.

restConnection = [[RestConnection alloc] initWithBaseURL:kServicesURL];
restConnection.delegate = self;

In viewWillAppear a request is built that points to the Person resource. That object is then used to load the data.

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    NSMutableURLRequest *request =
        [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:@"Person"]];
    [restConnection performRequest:request];
    [request release];
}

Finally, in the finishedReceivingData method, the table view is told to reload itself.

- (void)finishedReceivingData:(NSData *)data
{
    [self.tableView reloadData];
}

// Configure the cell.
NSDictionary *person = [restConnection.arrayData objectAtIndex:indexPath.row];
cell.textLabel.text = [NSString stringWithFormat:@"%@, %@",
                            [person objectForKey:@"lastName"],
                            [person objectForKey:@"firstName"]];

Selecting a table cell causes a new view controller to be created, PersonCarViewController. The view controller is told which person it should be displaying information about and then push it on the stack.

PersonCarViewController *vc =
    [[PersonCarViewController alloc] initWithNibName:@"PersonCarViewController" bundle:nil];
vc.person = [[restConnection arrayData] objectAtIndex:indexPath.row];
[self.navigationController pushViewController:vc animated:YES];
[PersonCarViewController release];

PersonCar

PersonCar represents a relationship between a person and their cars. The screen the right displays a list of a person's cars. Selecting a car will display its maintenance history.

This view controller is structured very similar to the Person view controller. The first difference is the request that gets built. Here cars are loaded for a specific person. The following code is used to format a URL which loads a person's resource, the associated PersonCars, and each PersonCars' Car.

NSString *resource = [NSString stringWithFormat:@"Person(%@)?$expand=PersonCar,PersonCar/Car", [person objectForKey:@"personID"]];

The syntax is a bit odd at first, most REST systems use a path component to specify unique identifiers, so it would be written like "Person/242134" instead of "Person(987234)". Other than that, we have the query string addition to expand the necessary information required by our UI.

So a request URI like this:

http://192.168.1.112/EDMTest/CarDealer.svc/Person(1)?$expand=PersonCar,PersonCar/Car

Would yield a response like this:

{"d":
    {"__metadata":
        {"uri":"http://192.168.1.112/EDMTest/CarDealer.svc/Person(1)",
         "type":"edmexampleModel.Person"},
     "personID":1,
     "firstName":"Bob",
     "lastName":"Samson",
     "ssn":"543872934",
     "createDate":"/Date(1257008908440)/",
     "PersonCar":[
        {"__metadata":
            {"uri":"http://192.168.1.112/EDMTest/CarDealer.svc/PersonCar(1)",
             "type":"edmexampleModel.PersonCar"},
         "personCarID":1,
         "createStamp":"/Date(1257103813990)/",
         "Car":
            {"__metadata":
                {"uri":"http://192.168.1.112/EDMTest/CarDealer.svc/Car(2)",
                 "type":"edmexampleModel.Car"},
             "carID":2,
             "make":"Ford",
             "model":"Explorer",
             "manufactureDate":"/Date(1099242508440)/",
             "createStamp":"/Date(1257008940840)/",
             "PersonCar":
                {"__deferred":
                    {"uri":"http://192.168.1.112/EDMTest/CarDealer.svc/Car(2)/PersonCar"}}},
         "Person":
            {"__deferred":
                {"uri":"http://192.168.1.112/EDMTest/CarDealer.svc/PersonCar(1)/Person"}},
         "PersonCarMaintenance":
            {"__deferred":
                {"uri":"http://192.168.1.112/EDMTest/CarDealer.svc/PersonCar(1)/PersonCarMaintenance"}}},
        {"__metadata":
            {"uri":"http://192.168.1.112/EDMTest/CarDealer.svc/PersonCar(2)",
             "type":"edmexampleModel.PersonCar"},
         "personCarID":2,
         "createStamp":"/Date(1257109628720)/",
         "Car":
            {"__metadata":
                {"uri":"http://192.168.1.112/EDMTest/CarDealer.svc/Car(5)",
                 "type":"edmexampleModel.Car"},
             "carID":5,
             "make":"Ford",
             "model":"Mustang",
             "manufactureDate":"/Date(1075680000000)/",
             "createStamp":"/Date(1257109563660)/",
             "PersonCar":
                {"__deferred":
                    {"uri":"http://192.168.1.112/EDMTest/CarDealer.svc/Car(5)/PersonCar"}}},
         "Person":
            {"__deferred":
                {"uri":"http://192.168.1.112/EDMTest/CarDealer.svc/PersonCar(2)/Person"}},
         "PersonCarMaintenance":
            {"__deferred":
                {"uri":"http://192.168.1.112/EDMTest/CarDealer.svc/PersonCar(2)/PersonCarMaintenance"}}}]}}

As you can see there is a lot of crap in there. I'll talk about __deferred and __metadata later on, there is plenty of discussion to be had about them.

The UI wants to display each description of each car for the person in context. This is done in cellForRowAtIndex as such.

NSDictionary *car = [[personCars objectAtIndex:indexPath.row] objectForKey:@"Car"];
cell.textLabel.text = [car objectForKey:@"model"];

Once a car has been selected in the table, the car's maintenance history should display. A new view controller is instantiated and the selected PersonCar information passed on.

PersonCarMaintenance

This view controller is very similar to the PersonCar VC. The purpose is to display a list of maintenance activities for the car in context.

This is the URL template that is used to get the required resources.

NSString *resource =
    [NSString stringWithFormat:@"Person(%@)?$expand=PersonCar,PersonCar/Car", [person objectForKey:@"personID"]];

And here is how we display the maintenance description.

NSDictionary *personCarMaintenance = [personCarMaintenances objectAtIndex:indexPath.row];
cell.textLabel.text =
    [[personCarMaintenance objectForKey:@"Maintenance"] objectForKey:@"description"];

Wrapping it up

So there you have it. I have discussed connecting an iPhone application an ADO.NET Data Service. Next time I'll talk more about this and discuss the CUD in CRUD.

Until next time, enjoy!

This is the third installment about using and accessing RESTful webservices on the iPhone.

There is no example project associated with this post.

Astoria

[ADO.NET] Data Services is Microsoft's way of turning EDM into web services. While researching the best way to access data stored in an SQL Server database from the iPhone, we decided to give Data Services a go around. Superficially it matched our broad criteria for the project's services layer:

• RESTful Interface,
• JSON payload support,
• Run on IIS,
• Easily access SQL Server

Accessing it on the iPhone turned out to be very simple. After it was accessible via a browser I began working on displaying a simple table from the database. I created the first version of RestConnection and I was able to get a list of data primitives out of the database and displayed in a UITableView in about an hour.

Atom is the default format for Data Services. You can specify JSON by setting the Accept header on your HTTP requests. JSON is much easier to deal with on the iPhone because of it's simpler format. However, if you have a good Atom handling methodology than that format maybe preferable.

Data Services has great functionality out of the box. Query options provide the ability to sort and filter result sets. The main thing that is missing is the ability to get a scalar value representing the results set (record/page counts). This has been addressed in the 4.0 version of the framework and will be available as part of the VS10 release (in beta already). See $inlinecount and $count for more information.

If you do a GET on the base service URL, it will return a service document. This xml contains information about the entities that are exposed via the Data Service.

If you append a /$metadata to your base service URL, you will get back an XML document containing Data Service Metadata. This information can be extremely useful for introspecting your Data Service. For example, it can be used in generating code to create a strongly typed business object.

This post has talked about ADO.NET Data Services and provided some useful links to get the basics down. Next time a coding example will show how to connect to a Data Service and parse the information, reusing and building on previous examples.

The next article can be found here.

{
    "myCoolObject" :
    [
        "value1",
        "value2"
    ]
}

This article will build on the previous post's project. Those classes will be modified and extended, as well as adding the BSJSONAdditions to the project. The primary focus of the changes will be on parsing the JSON data and displaying it in a UITableView.  If you have not yet downloaded the source for this example, you can do so here. This post is not about explaining what a UITableView is or does and assumes you know how to use one. Please referring to UITableView docs for more information.

// Returns a dictionary representation of the last data received.
@property (nonatomic, readonly) NSDictionary *dictionaryData;


...

- (NSDictionary *)dictionaryData
{
  return [NSDictionary dictionaryWithJSONString:[self stringData]];
}

- (void)finishedReceivingData:(NSData *)data
{
    NSLog(@"finishedReceivingData: %@", [restConnection stringData]);
    [activityIndicator stopAnimating];


    // Get the dictionary containing the raw parsed data.
    NSDictionary *rawData = [restConnection dictionaryData];


    // Get the interesting search results data for display to the user.
    [tableData release];
    tableData = [[[rawData objectForKey:@"responseData"] objectForKey:@"results"] retain];
    [mainTableView reloadData];
}