切片在结构中的初始化

Question

i am struggling with the initiation of a slice in a struct (GO-language). This may be easy, but still I can not solve it. I get

syntax error: unexpected var, expecting }
./test.go:28: no new variables on left side of :=
./test.go:29: non-name g.s on left side of := is the code;

I believe that s should be declared as part of the struct, so wonder why I get that error. Someone got some advice?

package main

import "fmt"

type node struct {
value int
}

type graph struct {
nodes , edges int
var s []int
} 

func main() {
g:= graphCreate()
}

func input(tname string)(number int){
fmt.Println("input a number of " + tname)
fmt.Scan(&number)
return 
}

func graphCreate()(g graph){
g:= graph{input("nodes"), input("edges")}
g.s := make([]int, 100)
return 
}

Answer 1

You have a few errors :

• g.s is already defined by the type graph when g is of type graph. So it's not a "new variable"
• you can't use var inside a type declaration
• you have g already declared (as a return type) in your graphCreate function
• when you write a literal struct, you must pass none or all the field values or name them
• you must use the variables you declare

here's a compiling code :

package main

import "fmt"

type node struct {
    value int
}

type graph struct {
    nodes, edges int
    s            []int // <= there was var here
}

func main() {
    graphCreate() // <= g wasn't used
}

func input(tname string) (number int) {
    fmt.Println("input a number of " + tname)
    fmt.Scan(&number)
    return
}

func graphCreate() (g graph) { // <= g is declared here
    g = graph{nodes:input("nodes"), edges:input("edges")} // <= name the fields
    g.s = make([]int, 100) // <= g.s is already a known name
    return
}