This is a creation in Article, where the information may have evolved or changed. This will be a short post, inspired by Sean Kelly's November Twitter. > I found a reason to use the specified return value in Golang and now I feel tears. > -sean Kelly (@StabbyCutyou) November 15, 2017 the goal is to remember A case where a named return variable is necessary, so let's get to the point. Imagine you're writing code that uses potentially panic functions, and you can't change those functions for whatever reason (third-party libraries, backwards compatibility, and so on). "' Gofunc Pressbutton () {fmt. Println ("I ' m Mr meeseeks, look at me!!") Other stuff and happens, but if Jerry asks to//remove 2 strokes from his golf game...panic ("It ' s gettin ' weird!")} You still need to use that function, but if it happens and you want to capture the panic and return it as an error, you should write something like this: "' Gofunc Dostuff () error {var err error//if T Here are a panic we need to recover in a deferred funcdefer func () {if r: = Recover (); r! = Nil {err = errors. New ("The Meeseeks went crazy!")}} () Pressbutton () Return err} ' execute it on Go Playground-Https://play.golang.org/p/wzkjKGqFPL after you Go run your code however ... What is it? Your error is a ' nil ' value, even when the code has an exception. It's not what we want! # # Why is this happening? Although initially it seemed that our code returned the ' var err error ' that we created at the beginning of the function, the fact that our processThe order will never reach this line of code. This means that it never returns a specific ERR variable, and changes it within our defer function, eventually becoming meaningless. Adding a ' Println ' after calling ' Pressbutton ', but before returning, does help to illustrate this point: ' Gopressbutton ()//Nothing below here gets executed!fmt. Println ("We Got here!") return err "' Execute it on Go Playground-https://play.golang.org/p/Vk0DYs20eB## How we fix it in order to fix this problem, we can Simply use the name to return the variable. "' Gofunc Dostuff (err Error) {//If there is a panic we need to recover in a deferred funcdefer func () {If r: = Recove R (); R! = Nil {err = errors. New ("The Meeseeks went crazy!")}} () Pressbutton () return err} ' executes it on Go Playground-Https://play.golang.org/p/bqGOroPjQJ The final code looks very similar, but by naming our return variable, When we declare this function, our program will return the ' ERR ' variable immediately, even if we never touched the return statement at the end of the ' dostuff ' function. Due to this subtle difference, we can now change the ' err ' variable in our defer function and successfully capture this panic.
via:https://www.calhoun.io/using-named-return-variables-to-capture-panics-in-go/
Author: Jon Calhoun Translator: Maple24 proofreading: polaris1119
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