Interface Error Handling
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Software Error Handling Best Practice
hiring developers or posting ads with us Programmers Questions Tags Users Badges Unanswered Ask Question error handling design pattern _ Programmers Stack Exchange is a question and answer site for professional programmers interested in conceptual questions about software development. Join them; it only interface errors takes a minute: Sign up Here's how it works: Anybody can ask a question Anybody can answer The best answers are voted up and rise to the top The modern way to perform error handling… up vote 104 down vote favorite 30 I've been pondering this problem for a while now and find myself continually finding caveats and contradictions, so I'm hoping someone can produce a conclusion to the following: Favour exceptions over error codes As far as I'm aware, from working in the industry for four years, reading books and blogs, etc. the current best practice for handling errors is to throw exceptions, rather than returning error codes (not necessarily an error code, but a type representing an error). But - to me this seems to contradict... Coding to interfaces, not implementations We code to interfaces or abstractions to reduce coupling. We don't know, or want to know, the specific type and implementation of an interface. So how can we possibly know what exceptions we should be looking to catch? The implementation could throw 10 different exceptions, or it could throw none. When we catch an exception surely we're making assumptions about the implementation? Unless - the interface has... Exception specifications Some languages allow developers to state that certain methods throw certain exceptions (Java for example, uses the throws keyword.) From the calling code's point of view this seems fine - we know explicitly which exceptions we might need to catch. But - this seems to suggest a... Leaky abstraction Why should an interface specify which exceptions can be thrown? What if the implementation doesn't need to throw an exception, or needs to throw other exceptions? There's no way, at an interface level, to know which exceptions an implementation may want to throw. So... To conclude Why are exceptions preferred when they seem (in my eyes) to contradict software best practices? And, if error codes are so bad (and I don't need to be sold on the vices of error codes), is there another alternative? What is the current (or soon to be) stat
application handles errors can have a big impact on user satisfaction and usability, and so error handling deserves close attention from user interface designers. Errors are unexpected or undesirable situations that prevent the normal operation of the application. We might classify errors by their general types and severities: The worst type of error is the unrecoverable crash, where the program abruptly stops due to a programming error that usually involves an unforeseen situation. Extensive testing and careful code inspections can reduce but never completely eliminate the possibility http://programmers.stackexchange.com/questions/147059/the-modern-way-to-perform-error-handling of such cases in a complex system. Technical errors are programming errors that prevent some task or action from being completed, but do not crash the entire application. Transient technical errors are situations that arise that temporarily hinder proper operation, but which can usually be corrected by taking actions outside of the application. For example, a database connection or network connection http://architectingusability.com/2012/06/05/designing-error-handling-for-maximum-usability-in-your-application/ might be lost, a disk is full, etc. Data validation or rule violation errors are cases where the application has detected that the data does not meet some criteria for validity. The system cannot function correctly if the data remains in this state, and so the user is notified and the user is expected to correct the data. Warnings are cases where the application detects a situation that doesn't prevent operation but which may have consequences that the user might not want or expect. We should also note that if the system interacts with the real world, programming mistakes and invalid data can lead to "error-like situations" in the world. For instance, if your application prints out checks but the address on the check or envelope omits the postal code, they may not be deliverable by the postal system, and the recipients won't receive their checks. Errors usually occur as a result of the user taking some action, although sometimes a system will report an error "out of the blue" when a background process has encountered a failure or when some
Mailing List Go on Google+ Go+ Community Go on Twitter Blog index The Go Blog Error handling and Go 12 July https://blog.golang.org/error-handling-and-go 2011 Introduction If you have written any Go code you have probably encountered the built-in error type. Go code uses error values to indicate an abnormal state. For example, the os.Open function returns a non-nil error value when it fails to open a file. func Open(name string) (file *File, err error) The following code uses os.Open to open a file. If error handling an error occurs it calls log.Fatal to print the error message and stop. f, err := os.Open("filename.ext") if err != nil { log.Fatal(err) } // do something with the open *File f You can get a lot done in Go knowing just this about the error type, but in this article we'll take a closer look at error and discuss interface error handling some good practices for error handling in Go. The error type The error type is an interface type. An error variable represents any value that can describe itself as a string. Here is the interface's declaration: type error interface { Error() string } The error type, as with all built in types, is predeclared in the universe block. The most commonly-used error implementation is the errors package's unexported errorString type. // errorString is a trivial implementation of error. type errorString struct { s string } func (e *errorString) Error() string { return e.s } You can construct one of these values with the errors.New function. It takes a string that it converts to an errors.errorString and returns as an error value. // New returns an error that formats as the given text. func New(text string) error { return &errorString{text} } Here's how you might use errors.New: func Sqrt(f float64) (float64, error) { if f < 0 { return 0, errors.New("math: square root of negative number") } // implementation } A caller passing a negative argument to Sqrt receives a