Printing NSData using NSLog

How can I print the contents of an NSData object using NSLog:

-(void) post:(NSString*) msg to:(NSString*) link{
    NSString *myRequestString = [NSString stringWithFormat:@"message=%@", msg];
    NSData *myRequestData = [NSData dataWithBytes: [myRequestString UTF8String] length: [myRequestString length]];
    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL: [NSURL URLWithString: link]]; 
    [request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"content-type"];
    [request setHTTPMethod: @"POST"];
    [request setHTTPBody: myRequestData];
    NSData *returnData = [NSURLConnection sendSynchronousRequest: request returningResponse: nil error: nil];
    NSLog("%@", *returnData); //doesn't work

}

I would like to print the contents of *returnData...

Convert NSData to NSString using

NSString *strData = [[NSString alloc]initWithData:returnData encoding:NSUTF8StringEncoding];

and print NSString in NSLog like below

NSLog(@"%@",strData);

This answer is edited for JeremyP, as he does not know how to know content is of UTF-8, though it was not a discussion of this question.

You can get response header in following delegate method

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;
NSDictionary *dic = [httpResponse allHeaderFields];
}

This dictionary will give you entire header info like below

<CFBasicHash 0x5a45e40 [0x24b2380]>{type = immutable dict, count = 7,
entries =>
0 : <CFString 0x5d1bf60 [0x24b2380]>{contents = "X-Aspnet-Version"} = <CFString 0x5d21a60 [0x24b2380]>{contents = "2.0.50727"}
1 : <CFString 0x41a03a8 [0x24b2380]>{contents = "Server"} = <CFString 0x5d272f0 [0x24b2380]>{contents = "Microsoft-IIS/6.0"}
2 : <CFString 0x41a0010 [0x24b2380]>{contents = "Content-Length"} = <CFString 0x5d28630 [0x24b2380]>{contents = "385"}
6 : <CFString 0x419ff48 [0x24b2380]>{contents = "Cache-Control"} = <CFString 0x5d29c70 [0x24b2380]>{contents = "private, max-age=0"}
10 : <CFString 0x5d1c640 [0x24b2380]>{contents = "X-Powered-By"} = <CFString 0x5d26f10 [0x24b2380]>{contents = "ASP.NET"}
11 : <CFString 0x41a0060 [0x24b2380]>{contents = "Content-Type"} = <CFString 0x5d29c90 [0x24b2380]>{contents = "text/xml; charset=utf-8"}
12 : <CFString 0x41a0088 [0x24b2380]>{contents = "Date"} = <CFString 0x5d27610 [0x24b2380]>{contents = "Fri, 08 Jul 2011 15:23:10 GMT"}
} 

Check charset="utf-8", you will get encoding from here.

If you do this:

NSLog(@"%@", returnData); 

The NSData will be logged in hex format. I think that is probably what you are after.

If you want to turn it into a string and log the string, you first need to find out what character set was used. The default character set for HTTP is not UTF-8, it is ISO-8859-1. One way to do that is to examine the Content-Type header for the charset section.

One thing you must consider too:

NSLog(@"%@", *returnData); // this is wrong.

NSLog(@"%@", returnData); // this is correct.

I hope I could help!

I somewhat often want to see what the NSData actually represent. Usually it's some sort of text, which makes hex a bit inconvenient. Therefore I usually write this snippet in the JavaScript console in my web browser, works pretty fast and can be modified easily if some continued processing would be wanted.

1. Copy/paste the following script into your browser console (right click here -> Inspect element), hit enter

   (function nsDataHexToString() {
       var str = prompt("Paste the hex string here:", "ié. 48656c6c 6f207468 657265...")
       var chs = str.replace(/[^A-F0-9]/ig,"").split("")
       var res = ""
       var cnt = 2
       for (var i = 0; i+cnt-1<chs.length; i+=cnt) {
           var nr = ""
           for (var j=0; j<cnt; j++)
               nr += chs[i+j]
           nr = parseInt(nr, 16)
           res += String.fromCharCode(nr)
       }
       console.log(res)
       return res
   })()
   

2. Run your swift/obj-c code, put in a breakpoint and inspect your NSData object

   let sample = "Hello there"
   let data = sample.dataUsingEncoding(NSUTF8StringEncoding)
   // Put breakpoint here, hover over "data", and press the eye/i
   

3. Copy the hex (something like <48656c6c 6f207468 657265>) and paste into the browser prompt

4. The console will then show a string: "Hello there"

Most recently, it was to inspect the output from NSAttributedString.dataFromRange, the rtfd was using a bit different encoding, but I got what I needed :) Also useful for some json conversion issues, etc.

Good luck :)