nserror - w3toppers.com

How get the list of errors thrown by a function?

When the Swift docs says a function throws, they mean that it throws an ErrorType (in Cocoa APIs usually an NSError), not an exception. Consider the following do-try-catch flow for NSFileManager‘s createDirectoryAtPath: let documentsPath = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0] do { try NSFileManager.defaultManager().createDirectoryAtPath(documentsPath, withIntermediateDirectories: false, attributes: nil) } catch { // ‘error’ variable automatically populated print(error) … Read more

Swift doesn’t convert Objective-C NSError** to throws

Only Objective-C methods are translated to throwing Swift methods, which do return a BOOL (not lower-cased bool), or a nullable-object. (Tested with Xcode 11.7, and Swift 5 language.) The reason is that Cocoa methods always use a return value NO or nil to indicate the failure of a method, and not just set an error … Read more

How can I use NSError in my iPhone App?

Well, what I usually do is have my methods that could error-out at runtime take a reference to a NSError pointer. If something does indeed go wrong in that method, I can populate the NSError reference with error data and return nil from the method. Example: – (id) endWorldHunger:(id)largeAmountsOfMonies error:(NSError**)error { // begin feeding the … Read more

HTTP status code 0 – Error Domain=NSURLErrorDomain?

There is no HTTP status code 0. What you see is a 0 returned by the API/library that you are using. You will have to check the documentation for that.

Objective-C Exceptions

It is unsafe to throw exceptions in circumstances where resources are not automatically managed. This is the case of the Cocoa framework (and neighbor frameworks), as they use manual reference counting. If you throw an exception, any release call you skip over by unwinding the stack will result in a leak. This should limit you … Read more