undefined attributes in an slice of node structs - go

Question

er, I am trying to learn go by implementing a random graph. I get an error on n.value undefined (type int has no field or method value), and n.neigbours undefined (type int has no field or method neigbours). I can not understand that compilation error as i create a new slice of nodesnr size of empty nodes in the g.nodes = make([]node, g.nodesnr). What is the problem?
package main
import (
"fmt"
//"math/rand"
)
type node struct {
value int
neigbours []int
}
type edge struct {
source int
sink int
}
type graph struct {
nodesnr, edgesnr int
nodes []node
edges chan edge
}
func main() {
randomGraph()
}
func input(tname string) (number int) {
fmt.Println("input a number of " + tname)
fmt.Scan(&number)
return
}
func randomGraph() (g graph) {
g = graph{nodesnr: input("nodes"), edgesnr: input("edges")}
g.addNodes()
for i := 0; i < g.nodesnr; i++ {
fmt.Println(g.nodes[i].value)
}
//g.addEdges()
return
}
func (g *graph) addNodes() {
g.nodes = make([]node, g.nodesnr)
for n := range g.nodes {
n.value = 2
n.neigbours = nil
return
}
}
func (g *graph) addEdges() {
g.edges = make(chan edge)
for i := 0; i < g.edgesnr; i++ {
//g.newEdge()
return
}
}
/*
func (g* graph) newEdge(){
e := new(edge)
e.source, e.sink = rand.Intn(g.nodesnr), rand.Intn(g.nodesnr)
g.edges <-e*
//g.addEdge()
}
*/
func (g *graph) edgeCheck(ep *edge) string {
if ep.source == ep.sink {
return "self"
}
//if(g.neigbourCheck(g.nodes[ep.source].neigbours, ep.sink) OR g.neigbourCheck(g.nodes[ep.sink].neigbours, ep.source){
// return "present"
return "empty"
}
func (g *graph) neigbourCheck(neigbours []node, node int) bool {
for neigbour := range neigbours {
if node == neigbour {
return true
}
}
return false
}
func (g *graph) addEdge() {
e := <-g.edges
switch etype := g.edgeCheck(&e); etype {
case "present":
fallthrough
case "self":
fmt.Println("self")
//go g.newEdge()
case "empty":
//g.nodes[e.source] = append(g.nodes[e.source], e.sink),
//g.nodes[e.sink] = append(g.nodes[e.sink], e.source)
fmt.Println("empty")
default:
fmt.Println("something went wrong")
}
}
Playground

Answer 1

Your error lies on line 47
for n := range g.nodes
When iterating over a slice, when using only one value, that value (n) will be set to the index, which is of type int. What you need to do is to change the line to:
for _, n := range g.nodes
This means that you discard the index but put the value in n instead.
Edit
n will be a copy of the value which means any changes made to n will not affect the node in the slice. To edit the node in the slice, you should actually get the index instead of the value:
for i := range g.nodes {
g.nodes[i].value = 2
g.nodes[i].neigbours = nil
return
}