问题
Generally, while performing GET or POST calls in iOS using dataTaskWithRequest or sendAsynchronousRequest we use to face network related errors with error codes like,
- NSURLErrorNotConnectedToInternet = -1009
- NSURLErrorCannotConnectToHost = -1004
- NSURLErrorTimedOut = -1001
In my case i'm disconnecting the internet and performing service calls. So, the expected error code is "NSURLErrorNotConnectedToInternet = -1009". But, its throwing "NSURLErrorCannotConnectToHost = -1004" like below,
Error Domain=NSURLErrorDomain Code=-1004 "Could not connect to the
server." UserInfo=0x1700f0e00 {NSUnderlyingError=0x170255e70 "The
operation couldn’t be completed. (kCFErrorDomainCFNetwork error
-1004.)", NSErrorFailingURLStringKey=https://example.com/reg,
NSErrorFailingURLKey=https://example.com/reg, _kCFStreamErrorDomainKey=1,
_kCFStreamErrorCodeKey=51, NSLocalizedDescription=Could not connect to the server.}
So, how to get the exact error status while using dataTaskWithRequest or sendAsynchronousRequest.
回答1:
As a rule, IIRC, the OS sends "not connected to Internet" only in two situations:
- The network is determined to be nonfunctional after:
- One or more URL requests fail and
- The OS tries to probe a well-known captive-portal-detection URL and
- That request also fails
- No interface has an IP address
- Including any connected VPNs
- Excluding loopback interface
Up until the system reaches that state, the failures you see will be "cannot connect to host", because that's all the OS knows for certain.
As a rule, your app should interpret these in the same way — by using reachability to determine when to try again, then trying again when reachability changes.
来源：https://stackoverflow.com/questions/37208917/error-domain-nsurlerrordomain-code-1004-instead-of-1009-in-swift-service-calls