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Cannot Use Nil As Type In Return Argument

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reply | permalink Caleb Spare (Although, after briefly glancing at your larger code sample, it does look like the kind of thing where I'd expect to see a *Node passed around, Consider code where a json document is deserialized into a struct consisting of normal string properties. package main import ( "encoding/json" Browse other questions tagged string go or ask your own question. Incorrect: package main import ( "fmt" "time" ) func main() { data := []string{"one","two","three"} for _,v := range data { go func() { fmt.Println(v) }() } time.Sleep(3 * time.Second) //goroutines print: have a peek here

The app should work. You can grow and shrink them without affecting other inner slices. The buggy example can be fixed by using a special cancellation channel to signal the remaining workers that their results are no longer neeeded. bytes.Equal() considers "nil" and empty slices to be equal. http://stackoverflow.com/questions/12703243/golang-what-is-the-zero-for-string

Cannot Use Nil As Type In Return Argument

Programmers absolutely shouldnot be checking for the zero value of the main return type to determine ifthere was an "error" condition.Some good exceptions to #2 are functions like strings.Index, becausenot finding If you want you can represent a unary NOT operation (e.g, NOT 0x02) with a binary XOR operation (e.g., 0x02 XOR 0xff). To unsubscribe from this group and stop receiving emails from it, send an email to [email protected] But only with actual pointers or references (a slice is a common example).

The operator precedence is not always the same though. wrong.There's no better way to solve this problem? package main import ( "fmt" "encoding/json" ) type MyData struct { One int two string } func main() { in := MyData{1,"two"} fmt.Printf("%#v\n",in) //prints main.MyData{One:1, two:"two"} encoded,_ := json.Marshal(in) fmt.Println(string(encoded)) //prints Golang Nil Struct Instead of "AAAAsuffix/BBBBBBBBB" you ended up with "AAAAsuffix/uffixBBBB".

returning a mutable instance of Node, when in actuality no Node is available - it seems misleading at best, but really, it just seems... Golang Check String Empty However, you'll also see this: fatal error: all goroutines are asleep - deadlock! Even then they can include other data using escape sequences. https://groups.google.com/d/topic/Golang-Nuts/4yBldwsjZwo All other goroutines are stuck trying to send their results.

reply | permalink Rasmus Schultz is too slow/memory-intensive for your needs and (b) you have benchmarks and profiles that prove that passing around the whole struct is the bottleneck. Use Of Untyped Nil Declaring a boolean value initializes it to false, declaring one of “nil-able types” initializes it to Zero Value which is corresponding (typed) nil value. Fails: package main func main() { m := make(map[string]int,99) cap(m) //error } Compile Error: /tmp/sandbox326543983/main.go:5: invalid argument m (type map[string]int) for cap Strings Can't Be "nil" level: beginner This is a A lot of these gotchas may seem obvious if you took the time to learn the language reading the official spec, wiki, mailing list discussions, many great posts and presentations by

Golang Check String Empty

Status changed to Accepted. http://grokbase.com/t/gg/golang-nuts/129xt1mqxc/go-nuts-proper-return-statement-for-a-struct-in-a-function For instance, it's used for errors allover:http://golang.org/src/pkg/net/udpsock.go?s=191:270For that matter, it shouldn't really exist at all - and yeah, I know, I still need to add an error value to the return Cannot Use Nil As Type In Return Argument There's an exception though. Golang Return Nil When the http library sees this response header it will also close the connection.

Fails: package main func main() { var x string = nil //error if x == nil { //error x = "default" } } Compile Errors: /tmp/sandbox630560459/main.go:4: cannot use nil as type navigate here Reverse a hexadecimal number in bash A guy scammed me, but he gave me a bank account number & routing number. Another option is to use the full slice expression. If reusing the http connection is important for your application you might need to add something like this at the end of your response processing logic: _, err = io.Copy(ioutil.Discard, resp.Body) Golang Nil

If you forget about this behavior it can lead to unexpected memory usage if your application allocates large temporary slices creating new slices from them to refer to small sections of By default, the standard http library will close the network connections only when the target HTTP server asks for it. This means you can still end up with a leak. http://homeshareware.com/cannot-use/cannot-use-the-connection-type.html package main import ( "fmt" "net/http" "io/ioutil" ) func main() { resp, err := http.Get("https://api.ipify.org?format=json") if err != nil { fmt.Println(err) return } defer resp.Body.Close()//ok, most of the time :-) body,

Rasmus Schultz at Dec 24, 2013 at 1:02 am ⇧ No wait, I think I got it...! :-)I should add a CanPop() method instead, right?The consumer code will have better/simpler semantics Golang String Pointer Make sure to check out the "norm" package (golang.org/x/text/unicode/norm) if you need to work with characters. Wouldyou use *byte just to make it nil when there's an error?2) Anyone calling a function that returns an error should be checking theerror before anything else.

returning a mutable instance of Node, when in actuality no Node is available - it seems misleading at best, but really, it just seems...

Already have an account? wrong.There's no better way to solve this problem? It happened because both directory slices referenced the same underlying array data from the original path slice. Golang Zero Value package main import "fmt" type SomeStruct struct { name string } func main() { s := getSomeStruct() fmt.Println(s.name) // It will crash here } func getSomeStruct() *SomeStruct { return nil //

package main import "fmt" type data struct { name string } func main() { s := []data {{"one"}} s[0].name = "two" //ok fmt.Println(s) //prints: [{two}] } Note that a while ago reply | permalink Caleb Spare In this case, I think returning a *Node and returning nil when there are no items available is fine. package main import ( "fmt" "unicode/utf8" ) func main() { data := "é" fmt.Println(len(data)) //prints: 3 fmt.Println(utf8.RuneCountInString(data)) //prints: 2 } Missing Comma In Multi-Line Slice, Array, and Map Literals level: beginner this contact form package main import "fmt" func main() { fmt.Printf("0x2 & 0x2 + 0x4 -> %#x\n",0x2 & 0x2 + 0x4) //prints: 0x2 & 0x2 + 0x4 -> 0x6 //Go: (0x2 & 0x2) +

This is a common mistake for beginners in general. wrong.There's no better way to solve this problem? You'll need to create a custom http transport configuration for it. package main import "fmt" func main() { data := "A\xfe\x02\xff\x04" for _,v := range data { fmt.Printf("%#x ",v) } //prints: 0x41 0xfffd 0x2 0xfffd 0x4 (not ok) fmt.Println() for _,v :=

How safe is 48V DC? Wouldyou use *byte just to make it nil when there's an error?2) Anyone calling a function that returns an error should be checkingthe error before anything else. See TestConvert below. This is fairly common fortypes that cannot be consts.

Fails: package main import "fmt" func main() { x := "text" x[0] = 'T' fmt.Println(x) } Compile Error: /tmp/sandbox305565531/main.go:7: cannot assign to x[0] Works: package main import "fmt" func main() { String pointers in GoLang can be nil A good rule of thumb is to use normal strings unless you need nil. returning a mutable instance of Node, when in actuality no Node is available - it seems misleading at best, but really, it just seems... package main import ( "fmt" "os" "path/filepath" ) func main() { if len(os.Args) != 2 { os.Exit(-1) } start, err := os.Stat(os.Args[1]) if err != nil || !start.IsDir(){ os.Exit(-1) } var

That's not so great :-) What's going on? package main import ( "fmt" "sync" ) func main() { var wg sync.WaitGroup done := make(chan struct{}) workerCount := 2 for i := 0; i < workerCount; i++ { wg.Add(1) go So my only options are, change the method signature to return *Node, which I don't want, for the reasons you explained - or construct and return a "dummy" Node instance whenever Programmers absolutely shouldnot be checking for the zero value of the main return type to determine ifthere was an "error" condition.Some good exceptions to #2 are functions like strings.Index, because notfinding

You reslice the path to reference each directory modifying the first folder name and then you combine the names to create a new path. Depending on the machine where you are running the code, the receiver goroutine may or may not have enough time to process the message before the sender continues its execution. share|improve this answer edited May 6 '13 at 11:41 answered Oct 3 '12 at 6:51 Denys Séguret 215k28420471 Your right dystroy, thing's working. –DeanSinaean Oct 4 '12 at 4:15 This could explain why ^ is reused to represent unary NOT operations.

Nil is a typed value Type information is inherent part of a nil value in Go. It wasn't important enough to support at that point in time, so it's still on the todo list. Using Pointer Receiver Methods On Value Instances level: advanced It's OK to call a pointer receiver method on a value as long as the value is addressable.

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