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Cocoa Error Handling Programming Guide


Which is the most "Objective-C friendly"? userInfo:...]; } return NO;}Exceptions Are Used for Programmer ErrorsObjective-C supports exceptions in much the same way as other programming languages, with a similar syntax to Java or C++. This is exactly what the Apple docs say on using NSError vs Exceptions. They serve different purposes and should not be confused.Exceptions (represented by NSException objects) are for programming errors, such as an array index that is out of bounds or this content

Displaying NSError Objects Once you get an NSError object back from a method there are a lot of things that can be done with it. If it is no longer nil I know that an error occurred and that I need to display it to the user. Retype URL.", nil); break; case NSURLErrorCannotConnectToHost: errorMsg = NSLocalizedString(@"Cannot connect to specified host. But how does the other side of that call work?

Ios Error Handling Best Practices

This is the express train to productivity for every Java developer who has dreamed of developing for Mac OS X or iPhone, but felt that Objective-C was too intimidating. It's good, but: Report typos, inaccuracies, and so forth. Browse other questions tagged iphone objective-c error-handling or ask your own question. Generated Sun, 20 Nov 2016 01:55:41 GMT by s_fl369 (squid/3.5.20)

Next Copyright © 2002, 2013 Apple Inc. You could extract the localized description (or failure reason), recovery suggestion, and the recovery options from the error object and use them to initialize the tiles and message text of an Guides and Sample Code Developer Search Search Guides and Sample Code Error Handling Programming Guide PDF Companion File Table of Contents Jump To… Download Sample Code NextPrevious Using and Creating Error Cocoa Error -1 Disk Utility If you’re making a remote web request, for example, you might try making the request again with a different server.

I'm fairly sure this is simply to keep the examples short and sweet. What Is Cocoa Error -1 Otherwise, use NSError objects. Consider the following code: Objective-C - (id)fetchDocument:(NSURL*)url error:(NSError**)error { NSString *myString = [[NSString alloc] initWithContentsOfURL:url]; //start to do something wickedly cool with the data if (YES) { //An error occurred NSMutableDictionary What about 2?

By utilizing an NSError in this manner, I am able to return anything I need when the method is successful and still able to send back all of the error information The Operation Couldn T Be Completed Cocoa Error 1 Apple provides a built in method to do this with a call to presentError: on the NSApplication instance. Of course, to make a successful evaluation of an error, you have to anticipate the errors that might be returned from a method invocation. Guides and Sample Code Developer Search Search Guides and Sample Code Programming with Objective-C PDF Companion File Table of Contents Jump To… Download Sample Code NextPrevious Dealing with ErrorsAlmost every

What Is Cocoa Error -1

If you need to request data from a remote web service, for example, there are a variety of potential problems that may arise, including:No network connectivityThe remote web service may be Source These are the problems that you should find and fix during testing before you ship your app.All other errors are represented by instances of the NSError class. Ios Error Handling Best Practices I agree with this philosophy for many use cases because (a) it moves validity-checking to the moment of action, so in a sense it's more accurate, and (b, subjective) it's more How To Fix Cocoa Error -1 Download the Example Project Comments tompa says: April 6, 2008 at 1:01 am Reading this code makes me laugh: if (!error) { [NSApp presentError:error]; So, if not an error, then present

Guides and Sample Code Developer Search Search Guides and Sample Code Exception Programming Topics PDF Companion File Table of Contents Jump To… Download Sample Code Next Introduction to Exception Programming Topics news Listing 2-1 illustrates this approach.Listing 2-1Handling an NSError object returned from a AppKit methodNSError *theError;BOOL success = [myDoc writeToURL:[self docURL] ofType:@"html" error:&theError]; if (success == NO) { // Maybe try to minofifa says: March 17, 2009 at 4:35 am Hi Marcus I noticed in several of your NSError article examples, you give the status code number a seemingly random value. Also, the Cocoa library support you get for NSError is very good. Cocoa Error -1 Boomerang

To put it another way, by passing a pointer to the pointer, the receiving method can decide what your variable's value is. You usually take care of these sorts of errors with exceptions when an application is being created rather than at runtime.If you have an existing body of code (such as third-party Return the NSError object to describe the error. have a peek at these guys Join them; it only takes a minute: Sign up What are best practices for error handling when writing an API for the iphone?

The NSAlert class provides the alertWithError: method for this purpose.Listing 2-6Directly displaying an error alert dialogNSAlert *theAlert = [NSAlert alertWithError:theError];NSInteger button = [theAlert runModal];if (button != NSAlertFirstButtonReturn) { // Cocoa Error -1 Mac It will show them how to take their existing language knowledge and design patterns and transfer that experience to Objective-C and the Cocoa runtime library. And 12342 was what again?!?

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With an application there is an also an architecture allowing the various objects in an application to refine the information in an error object and perhaps to recover from the error. Once the dictionary is populated, I then initialized an NSError object using the helper method that gives me back an auto-released object. From memory this is what the Apple docs recommend. What Does Cocoa Error 1 Mean Is that the best approach?

But you should ensure that any expected runtime exceptions do not escape from these subsystems and end up in the caller’s code. All Rights Reserved. In the case of an NSArray, for example, you should always check the array’s count to determine the number of items before trying to access an object at a given index. http://trinitylabsupply.com/cocoa-error/cocoa-error-513.html Your input helps improve our developer documentation.

Exceptions are a huge pain when you don't have garbage collection, which is new in Objective-C and still not available on the iPhone. The objectAtIndex: method throws an exception if you make an out-of-bounds request so that you can find the bug in your code early in the development cycle—you should avoid throwing exceptions Instead of merely displaying an error message based on an NSError object, you could examine the object to determine if you can do something else. How to politely decline my salary due to feeling I don't currently deserve it?

Instead of exceptions, error objects (NSError) and the Cocoa error-delivery mechanism are the recommended way to communicate expected errors in Cocoa applications. Error objects returned from Cocoa methods can often contain underlying error objects representing errors returned by lower subsystems, such as the BSD layer (NSPOSIXErrorDomain). NSDictionary *errorDictionary = @{ NSLocalizedDescriptionKey : description, NSUnderlyingErrorKey : underlyingError, NSFilePathErrorKey : path }; *anError = [[NSError alloc] initWithDomain:MyCustomErrorDomain code:errCode userInfo:errorDictionary]; } return nil; } // ... Neither of those is pretty or easy to maintain.

In general, these methods should not indicate an error through the existence of an NSError object. If you’re working with a low-level C++ library that uses exceptions for error handling, for example, you might catch its exceptions and generate suitable NSError objects to display to the user.If So as I understand it, only use exceptions when something is fatally wrong. The interesting piece of code here is how I am referencing the passed in pointer.

Although Cocoa methods that indirectly return error objects in the Cocoa error domain are guaranteed to return such objects if the method indicates failure by directly returning nil or NO, more hot questions question feed lang-c about us tour help blog chat data legal privacy policy work here advertising info mobile contact us feedback Technology Life / Arts Culture / Recreation