Connecting my iPad app to a SQL Server - ios

Question

I have an iPad application that uses table view controllers to present lists of data. I want to connect these tables to data in a SQL Server. I have very little experience in this realm of programming and I am not sure where to begin. In the long run I'd like adding/editing/deleting data on the app to sync with the server as well. I understand that this is a very broad question, so I am mainly looking for suggestions to help me get started. I, for example, do not want to start researching and learning Core Data if it is not the framework that can accomplish my goal.
In short, how can I connect my application to a SQL Server so that I can access its data and sync it to a device? Any example code/walkthroughs would be much appreciated.

Answer 1

I am currently working in an iOS application that requires this same functionality. For mySQL database queries on the server, I am using server-side PHP scripts that can accept variables, such as the table name or database search term.
What I do is I make an HTTP GET request using objective-C's NSMutableURLRequest, then have the server process the request (in PHP), and then return the database query results to my application in JSON format. I use SBJsonParser to parse the returned data into an NSData, and then an NSArray object.
An example of making an HTTP request in Objective-C:
NSString *urlString = [NSString stringWithFormat:#"http://website.com/yourPHPScript.php?yourVariable=something"];
NSURL *url = [NSURL URLWithString: urlString];
NSMutableURLRequest *request1 = [[NSMutableURLRequest alloc] initWithURL:url];
/* set the data and http method */
[request1 setHTTPMethod:#"GET"];
[request1 setHTTPBody:nil];
/* Make the connection to the server with the http request */
[[NSURLConnection alloc] initWithRequest:request1
delegate:self];
There is more code that you need to add to actually respond to the request when it returns, and I can post an example of that if you would like.
I actually dont know if this is the best way to do this, but It has worked for me so far. It does require that you know PHP though, and I don't you if you have any experience with it.
UPDATE:
Here is some sample code showing how to respond to the request. In my case, since I am getting a JSON encoded response, I use the SBJsonParser to parse the response.
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
/* This string contains the response data.
* At this point you can do whatever you want with it
*/
NSString *responseString = [[NSString alloc] initWithData:receivedData
encoding:NSUTF8StringEncoding];
/* Here I parse the response JSON string into a native NSDictionary using an SBJsonParser */
SBJsonParser *parser = [[[SBJsonParser alloc] init] autorelease];
/* Parse the JSON into an NSDictionary */
NSDictionary *responseArr = [parser objectWithString:responseString];
/* Do whatever you want to do with the response */
/* Relsease the connection unless you want to re-use it */
[connection release];
}
Also add these methods, assuming you have an NSMUtableData instance variable titled receivedData.
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
[receivedData setLength:0];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
[receivedData appendData:data];
}

Answer 2

I would not recommend connecting directly to a SQL server. You could, in theory, try to compile FreeTDS or unixODBC for iOS. I did not try it, but from my experience, at least FreeTDS should be fairly portable.
However, there are many other (and for most purposes better and easier) way of synchronizing data with a SQL Server. For example, you could use RestKit on the iPad side and a simple REST service on the SQL Server side. Or you could use OData which has a iOS library (which I just recently learned about, I have to admit).