checking for bad NSURLConnection - objective-c

Question

i am new to Objective-C and going through the book, The Big Nerd Ranch Guide to Objective-C programming..
#import <Foundation/Foundation.h>
int main(int argc, const char * argv[])
{
#autoreleasepool {
NSURL *url = [NSURL URLWithString:#"http://www.google.com/imagess/logos/ps_logo2.png"];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
NSError *error =nil;
NSData *data = [NSURLConnection sendSynchronousRequest:request
returningResponse:NULL
error:&error];
if(!data){
NSLog(#"fetch failed %#", [error localizedDescription]);
return 1;
}
NSLog(#"the files is %lu bytes", [data length]);
BOOL written = [data writeToFile:#"/tmp/google.png"
options:NSDataWritingAtomic
error:&error];
if(!written){
NSLog(#"write failed: %#",[error localizedDescription]);
return 1;
}
NSLog(#"Success!");
NSData *readData = [NSData dataWithContentsOfFile:#"/tmp/google.png"];
NSLog(#"the file read from disk has %lu bytes", [readData length]);
}
return 0;
}
the problem is this, if i change the *url to http://aFakeDomain.com/imimimi/myImage.png then my data object will be nill because there is no HOST and everything works fine.. but if i use google as the domain and point to a bad file location then the data object stil has header info and is NOT nil thus i never get the error i should.
whats the best way to make sure that the *url successfully found a file.
thanks

Answer 1

You will need to pass a response to the NSURLConnection call and then check its status code:
NSHTTPURLResponse* httpResponse = (NSHTTPURLResponse*)response;
NSData *data = [NSURLConnection sendSynchronousRequest:request
returningResponse:&httpResponse
error:&error];
int code = [httpResponse statusCode];
you will get a 404 status code in your case.

Answer 2

NSUrlResponce *responce = nil;
NSData *data = [NSURLConnection sendSynchronousRequest:request
returningResponse:&responce
error:&error];
if (error) {
// handle the error
}
if (![[responce MIMEType] isEqualToString:#"image/png"]) {
// failed to get png file
}

Answer 3

There are also some mistakes of the file name;
instead of #"/tmp/google.png", you should use the code list blow:
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES);
NSString *filePath = [[paths objectAtIndex:0] stringByAppendingPathComponent:#"google.png"];