I'm curious if this is possible in Go. I have a type with multiple methods. Is it possible to have a function which takes a method argument and then call it for the type?
Here is a small example of what I would want:
package main import ( "fmt" ) type Foo int func (f Foo) A() { fmt.Println("A") } func (f Foo) B() { fmt.Println("B") } func (f Foo) C() { fmt.Println("C") } func main() { var f Foo bar := func(foo func()) { f.foo() } bar(A) bar(B) bar(C) }
Go thinks type Foo
has a method called foo()
, rather than replacing it with the passed in method name.
We cannot pass the function as an argument to another function. But we can pass the reference of a function as a parameter by using a function pointer.
Information can be passed into functions as arguments. Arguments are specified after the function name, inside the parentheses. You can add as many arguments as you want, just separate them with a comma.
We can't directly pass the whole method as an argument to another method. Instead, we can call the method from the argument of another method. // pass method2 as argument to method1 public void method1(method2()); Here, the returned value from method2() is assigned as an argument to method1() .
Yes, it's possible. You have 2 (3) options:
The expression Foo.A
yields a function equivalent to A
but with an explicit receiver as its first argument; it has signature func(f Foo)
.
var foo Foo bar := func(m func(f Foo)) { m(foo) } bar(Foo.A) bar(Foo.B) bar(Foo.C)
Here the method receiver is explicit. You only pass the method name (with the type it belongs to) to bar()
, and when calling it, you have to pass the actual receiver: m(f)
.
Output as expected (try it on the Go Playground):
A B C
If f
is a value of type Foo
, the expression f.A
yields a function value of type func()
with implicit receiver value f
.
var f Foo bar := func(m func()) { m() } bar(f.A) bar(f.B) bar(f.C)
Note that here the method receiver is implicit, it is saved with the function value passed to bar()
, and so it is called without explicitly specifying it: m()
.
Output is the same (try it on the Go Playground).
Inferior to previous solutions (both in performance and in "safeness"), but you could pass the name of the method as a string
value, and then use the reflect
package to call the method by that name. It could look like this:
var f Foo bar := func(name string) { reflect.ValueOf(f).MethodByName(name).Call(nil) } bar("A") bar("B") bar("C")
Try this on the Go Playground.
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