NSError NSURLError


NSError has information about error.

  • domain
  • code
  • userinfo

NSError code List : Apple Developer

NSError by myself


NSError*err = [NSError errorWithDomain:@"TestDomain" code:400 userInfo:nil];
NSError*err2 = [NSError errorWithDomain:NSErrorDomain code:NSURLTimeOut userInfo:nil];

NSURLError UIWebView, WKWebView related

– (void)webView:(UIWebView *)webView didFailLoadWithError:(NSError *)error for UIWebView, – (void)webView:(WKWebView *)webView didFailNavigation:(WKNavigation *)navigation withError:(NSError *)error, – (void)webView:(WKWebView *)webView didFailProvisionalNavigation:(WKNavigation *)navigation withError:(NSError *)error
These delegate methods return NSError. We can detect error from this.

Foundation Constants Reference

These list are some of them

Error Description
NSURLErrorNetworkConnectionLost Returned when a client or server connection is severed in the middle of an in-progress load. Once succeeding connect, but disconnect
NSURLErrorNotConnectedToInternet Returned when a network resource was requested, but an internet connection is not established and cannot be established automatically, either through a lack of connectivity, or by the user’s choice not to make a network connection automatically
NSURLErrorInternationalRoamingOff International roaming off by the device
NSURLErrorTimedOut timeout before completion
NSURLErrorUnknown Unknown
NSURLErrorBadURL Returned when a URL is sufficiently malformed that a URL request cannot be initiated
NSURLErrorUnsupportedURL Returned when a properly formed URL cannot be handled by the framework