CODEWITHSUNDEEP
iosobjective-ciphone
Crafti
Crafti

Reputation: 219

Objective-C getting data from a web page

I looked around but I could not find quite the solution to my problem anywhere.

The thing is I would like to get the data that is on a webpage of mine. For example, the content of my web page is "4|3|6" and I would like to have an array with 4,3,6.

I may say something stupid there but I don't really know if my page is XML or HTML, because when I check the source code it just shows "4|3|6" for example.

So is there any way to do this or am I going to have to look into parsers ? And also, how to know of what type my page is ? (it's name is typically "http://example.aspx?value=x" )

I know a lot of questions were asked about this and I apologize if I missed the one with my answer in it.

If it helps, here are the info on the page:

type: text/plain
Encoding: UTF-8

EDIT: So after trying Alex's version, it seems I can't get to retrieve the data. I think the problem is to get the NSString from the data, which is that line:

NSString *dataString = [[NSString alloc] initWithData:data          encoding:NSUTF8StringEncoding];

This line doesn't give me a crash, but when I try to display it using label.text=datastring;

it doesn't display anything. And when I try to assign an NSArray from datastring using the @"|" separator, and try for example to display the first item of that NSArray, it gives me that error about index being out of bounds.

I am not at work right now so I can't really test this but thanks for any ideas.

Upvotes: 0

Views: 5234

Answers (2)

zoul
zoul

Reputation: 104065

If the source code is just “4|3|6” it’s plain text. You can download it using NSURLConnection:

NSURL *targetURL = [NSURL URLWithString:@"…"];
NSURLRequest *request = [NSURLRequest requestWithURL:targetURL];
NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];

Then you can create a string from the data and parse it:

NSString *dataString = [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding];
NSArray *components = [dataString componentsSeparatedByString:@"|"];
[dataString release];

Now you’ll have the components in the resulting array. I’m assuming the data is encoded in ASCII, which might not be the case. And the download is synchronous, which means it will block the current thread. If you’re running the code on the main thread, you might want to dispatch it to a background thread so that you don’t block the UI. But that’s to worry about later, just get it working first.

As for the asynchronous download, I don’t like the asynchronous NSURLConnection interface, as it’s quite a lot of work for what it does. It’s a pity that NSURLConnection does not support blocks. You can find some NSURLConnection extensions with blocks on the web, but that means relying on third-party code, which carries its own possible problems. One easy way to get the download happening in background is this:

- (void) performDownload
{
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
    NSData *downloadedData = /* synchronous NSURLConnection */;
    [self performSelectorOnMainThread:@selector(downloadDidFinish:)
        withObject:downloadedData];
    [pool drain];
}

- (void) downloadDidFinish: (NSData*) data {
    NSLog(@"Data ready: %@", data);
}

- (void) startDownload {
    [self performSelectorInBackground:@selector(performDownload) withObject:nil];
}

But you should learn about threading, run loops and autorelease pools before you start using this code, so that you know what you are doing.

Upvotes: 2

Alex Coplan
Alex Coplan

Reputation: 13361

Download the text using NSURLConnection - see this sample code by Apple.

Your download method will look something like this:

NSURL *url = [NSURL urlWithString:@"http://example.aspx?value=x""];
NSURLRequest *req = [NSURLRequest requestWithURL:url];
NSURLConnection *con = [NSURLConnection connectionWithRequest:req delegate:self];

You then buffer the data in an NSMutableData instance - the Apple code explains this really well.

Once you have it, it's really easy to parse.

NSArray *myArray = [myString componentsSeparatedByString:@"|"];

Upvotes: 3

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