---
title: Introduction to Error Handling Programming Guide For Cocoa
framework: cocoa
role: article
path: apple-archive/documentation/Cocoa/Conceptual/ErrorHandlingCocoa/ErrorHandling
---

# Introduction to Error Handling Programming Guide For Cocoa

Describes NSError objects, related Application Kit support for error handling, and how to use these features in your code.

## Organization of This Document

*Error Handling Programming Guide for Cocoa* has the following articles:

- [Error Objects, Domains, and Codes](../ErrorObjectsDomains/ErrorObjectsDomains.html#//apple_ref/doc/uid/TP40001806-CH202-CJBGAIBJ) describes the attributes of an `NSError` object, particularly its domain and error code, and discusses the possible contents of an error object’s “user info” dictionary, including localized message strings and underlying errors. - [Using and Creating Error Objects](../CreateCustomizeNSError/CreateCustomizeNSError.html#//apple_ref/doc/uid/TP40001806-CH204-BAJIIGCC) explains how to evaluate an error, how to display an error message using an `NSError` object, and how to implement methods that return an `NSError` object by reference. - [Error Responders and Error Recovery](../ErrorRespondRecover/ErrorRespondRecover.html#//apple_ref/doc/uid/TP40001806-CH203-BAJCBIFC) describes the Application Kit architecture for passing error objects up a chain of objects in an application, giving each object a chance to customize the error before it is presented. It also discusses the role of the recovery attempter, an object designated to attempt a recovery from an error if the user requests it. - [Handling Received Errors](../HandleReceivedError/HandleReceivedError.html#//apple_ref/doc/uid/TP40001806-CH205-BAJEHAJC) discusses how, in the chain of error-responder objects, you handle a received error and customize it. - [Recovering From Errors](../RecoverFromErrors/RecoverFromErrors.html#//apple_ref/doc/uid/TP40001806-CH206-BCIDEGGF) explains the procedure for attempting a user-requested recovery from an error.

The two chapters relevant to iOS are [Error Objects, Domains, and Codes](../ErrorObjectsDomains/ErrorObjectsDomains.html#//apple_ref/doc/uid/TP40001806-CH202-CJBGAIBJ) and [Using and Creating Error Objects](../CreateCustomizeNSError/CreateCustomizeNSError.html#//apple_ref/doc/uid/TP40001806-CH204-BAJIIGCC) .

## See Also

“ [The Document Architecture Supports Robust Error Handling](../../../../DataManagement/Conceptual/DocBasedAppProgrammingGuideForOSX/StandardBehaviors/StandardBehaviors.html#//apple_ref/doc/uid/TP40011179-CH5-SW32) " in *[Document-Based App Programming Guide for Mac](../../../../DataManagement/Conceptual/DocBasedAppProgrammingGuideForOSX/Introduction/Introduction.html#//apple_ref/doc/uid/TP40011179)* offers valuable advice for subclasses that override methods with a by-reference `NSError` parameter.

<!--a target="_self" -->Types of Dialogs and When to Use Them<!--/a--> offers advice on the form and content of alerts in OS X. *iOS Human Interface Guidelines* offers similar advice for alerts on iOS. You should consult these guidelines before composing your error messages. Also take a look at the following documents discussing areas of Cocoa programming related to error handling and the presentation of error messages:

- *[Assertions and Logging Programming Guide](../../Assertions/Assertions.html#//apple_ref/doc/uid/10000014i)* (both platforms) - *[Dialogs and Special Panels](../../Dialog/Dialog.html#//apple_ref/doc/uid/10000071i)* (alerts on OS X) - *[Sheet Programming Topics](../../Sheets/Sheets.html#//apple_ref/doc/uid/10000002i)* (OS X) - *[UIAlertView Class Reference](https://developer.apple.com/documentation/uikit/uialertview)* (iOS)

*[Exception Programming Topics](../../Exceptions/Exceptions.html#//apple_ref/doc/uid/10000012i)* discusses how to raise and handle exceptions. [Exception Handling](../../ObjectiveC/Chapters/ocExceptionHandling.html#//apple_ref/doc/uid/TP30001163-CH13) in *[The Objective-C Programming Language](../../ObjectiveC/Introduction/introObjectiveC.html#//apple_ref/doc/uid/TP30001163)* describes the compiler directives `@try`, `@catch`, `@throw`, and `@finally`, which are used in exception handling.

[Next](../ErrorObjectsDomains/ErrorObjectsDomains.html)

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