How to download file from particular url?

Question

NSURL * url = @"http://192.168.100.161/UploadWhiteB/wh.txt";
NSData * data = [NSData dataWithContentsOfURL:url];

if (data != nil) {
  NSLog(@"\nis not nil");
  NSString *readdata = [[NSString alloc] initWithContentsOfURL:(NSData *)data ];

I write this code to download a file from given url... but i get an error on line
NSData * data = [NSData dataWithContentsOfURL:url];

uncaught exception...

so please help me out.

I don't know Objective-C, but why not catch the exception so you can print it out and find out more about what's going wrong? — Carl Smotricz, Apr 23 '10 at 06:10

score 4 · Answer 1 · answered Apr 23 '10 at 23:41

4

Your first line should be

NSURL * url = [NSURL URLWithString:@"http://192.168.100.161/UploadWhiteB/wh.txt"];

(NSURL is not a string, but can easily be constructed from one.)

I'd expect you to get a compiler warning on your first line--ignoring compiler warnings is bad. The second line fails because dataWithContentsOfURL: expects to be given a pointer to an NSURL object and while you're passing it a pointer that you've typed NSURL*, url is actually pointing to an NSString object.

answered Apr 23 '10 at 23:41

Isaac

10,668
5
59
68

Does the source of the `NSData` object matter for this method? [In this question](http://stackoverflow.com/questions/16150196/updating-sqlite-database-without-xml) I'm trying to download a .sqlite database into a `NSData` object from a URL, but it doesn't seem to be saving it correctly. The file is written, but when I try to access it (either through my app or with a 3rd party viewer) it tells me it's not a valid SQLite database. Does `dataWithContentsOfURL` only work for downloading .txt files or something like that? – GeneralMike Apr 25 '13 at 17:28

score 2 · Answer 2 · answered Nov 22 '11 at 10:33

2

    NSString *file = @"http://192.168.100.161/UploadWhiteB/wh.txt";
    NSURL *fileURL = [NSURL URLWithString:file];

    NSLog(@"qqqqq.....%@",fileURL);

    NSData *fileData = [[NSData alloc] initWithContentsOfURL:fileURL];

answered Nov 22 '11 at 10:33

Govind888

21
3

score 0 · Answer 3 · answered Apr 23 '10 at 06:21

-[NSString initWithContentsOfURL:] is deprecated. You should be using -[NSString (id)initWithContentsOfURL:encoding:error:]. In either case, the URL paramter is an NSURL instance, not an NSData instance. Of course you get an error trying to initialize a string with the wrong type. You can initialize the string with the URL data using -[NSString initWithData:encoding:], or just initialize the string directly from the URL.

How to download file from particular url?

3 Answers3

Linked