Go map of functions - dictionary

Question

I have Go program that has a function defined. I also have a map that should have a key for each function. How can I do that?
I have tried this, but this doesn't work.
func a(param string) {
}
m := map[string] func {
'a_func': a,
}
for key, value := range m {
if key == 'a_func' {
value(param)
}
}

Answer 1

Are you trying to do something like this? I've revised the example to use varying types and numbers of function parameters.
package main
import "fmt"
func f(p string) {
fmt.Println("function f parameter:", p)
}
func g(p string, q int) {
fmt.Println("function g parameters:", p, q)
}
func main() {
m := map[string]interface{}{
"f": f,
"g": g,
}
for k, v := range m {
switch k {
case "f":
v.(func(string))("astring")
case "g":
v.(func(string, int))("astring", 42)
}
}
}

Answer 2

m := map[string]func(string, string)
Works if you know the signature (and all the funcs have the same signature)
I think this is cleaner/safer than using interface{}

Answer 3

You can define a type if functions are same interface.
package main
import "log"
type fn func (string)
func foo(msg string) {
log.Printf("foo! Message is %s", msg)
}
func bar(msg string) {
log.Printf("bar! Message is %s", msg)
}
func main() {
m := map[string] fn {
"f": foo,
"b": bar,
}
log.Printf("map is %v", m)
m["f"]("Hello")
m["b"]("World")
}

Answer 4

#Seth Hoenig's answer helped me best, but I just wanted to add that Go accepts functions with defined return value as well:
package main
func main() {
m := map[string]func(string) string{
"foo": func(s string) string { return s + "nurf" },
}
m["foo"]("baz") // "baznurf"
}
If you think it's ugly, you could always use a type (see #smagch's answer).

Answer 5

I used a map[string]func (a type, b *type) I passed a string to search the map and a pointer to modify the slice.
Hope that helps!
var Exceptions map[string]func(step string, item *structs.Item)
func SetExceptions() {
Exceptions = map[string]func(a string, i *structs.Item){
"step1": step1,
}
}
func RunExceptions(state string, item *structs.Item) {
method, methBool := Exceptions[state]
if methBool {
method(state, item)
}
}
func step1(step string, item *structs.Item) {
item.Title = "Modified"
}

Answer 6

Here is the way I made it work in my case:
package main
import (
"fmt"
)
var routes map[string]func() string
func main() {
routes = map[string]func() string{
"GET /": homePage,
"GET /about": aboutPage,
}
fmt.Println("GET /", pageContent("GET /"))
fmt.Println("GET /about", pageContent("GET /about"))
fmt.Println("GET /unknown", pageContent("GET /unknown"))
// Output:
// GET / Home page
// GET /about About page
// GET /unknown 404: Page Not Found
}
func pageContent(route string) string {
page, ok := routes[route]
if ok {
return page()
} else {
return notFoundPage()
}
}
func homePage() string {
return "Home page"
}
func aboutPage() string {
return "About page"
}
func notFoundPage() string {
return "404: Page Not Found"
}
https://play.golang.org/p/8_g6Di1OKZS

Answer 7

Hope this works for you(you can use interface{} instead any)
package main
import (
"fmt"
)
func toon(v any) {
fmt.Println(v)
}
func main() {
names := map[string]any{
"Function": toon,
}
names["Function"].(func(any))("a")
}