Since S1 and S2 satisfy the Stringl interface just use that for your slice type and you get something like (note that you do not need to specify the variables types if you initialize them like you did).
https://play.golang.org/p/pJHU0Dq8t6 Le vendredi 5 mai 2017 13:35:42 UTC+2, eZio Pan a écrit : > > Hi, I'm a newbie in Golang. I get stuck in a problem that I can't > understand why. I wish someone could help me out. Thanks! > > There are 2 struct type *S1* and *S2*. Both of them implement interface > type *StringI*. > I write a function called *run* which use *StringI* interface as input, > and run all method *StringI* signatured. > > Then I write a test file, in which I declare a **S1* variable as *s1*, > and a **S2* variable as *s2*. > I create a slice *[]interface{}{s1,s2}*, the I use for loop to get item > in it. > > But when I use *run*(*LoopedItem*), I got an error > > *cannot use item (type interface {}) as type StringI in argument to run* > > And I use fmt.Printf("%T", *LoopedItem*), Golang does print right type -- > **S1* and **S2* > > Then I try type switch > > switch *LoopedItem*.(type){ > case *S1: > run(*LoopedItem*.(*S1)) > case *S2: > run(*LoopedItem*.(*S2)) > } > > Everything goes on well. > > > *I wonder why I can't use *LoopedItem* (as StringI interface) as run > function's argument,but *LoopedItem*.(*TypePointer*) (as struct type > pointer) to the run function.* > > > > Here is the source code > > > #### firstInter.go #### > > /*my first interface*/ > package firstInter > > import ( > "fmt" > "strconv" > ) > > // interface with Get() and Push() method > type StringI interface { > Get() string > Push(string) > String() string > } > > // type S1, store a int value > type S1 struct { > I int > } > > // S1's Get method > // return the int value it stored > func (s *S1) Get() string { > return strconv.Itoa(s.I) > } > > // S1's Push method > // put new value into S1 > func (s *S1) Push(a string) { > num, err := strconv.Atoi(a) > if err == nil { > s.I = num > } > } > > // S1's String method > // for fmt > func (s *S1) String() string { > return strconv.Itoa(s.I) > } > > // type S2, store a string value > type S2 struct { > S string > } > > // S2's Get method > // return the string value it stored > func (s *S2) Get() string { > return s.S > } > > // S2's Push method > // put new value into S2 > func (s *S2) Push(a string) { > s.S = a > } > > // S2's String method > // for fmt > func (s *S2) String() string { > return s.S > } > > // function to run every method > // StringI interface signatured > func run(tI StringI) { > fmt.Printf("%v\n", tI.Get()) > tI.Push("3") > fmt.Printf("%v\n", tI.Get()) > } > > > #### firstInter_test.go #### > > // firstInter package Unit Testing > package firstInter > > import ( > //"fmt" > ) > > var tI StringI > > var s1 *S1 = &S1{1} > var s2 *S2 = &S2{"???"} > var l []interface{} = []interface{}{s1, s2} > > func Example_InterFace() { > for _, item := range l { > // something wrong here > // run(item) > // fmt.Printf("%T\n", item) > switch item.(type) { > case *S1: > run(item.(*S1)) > case *S2: > run(item.(*S2)) > } > } > // Output: > // 1 > // 3 > // ??? > // 3 > } > > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
