[function] Can functions be passed as parameters?

In Java I can do something like

derp(new Runnable { public void run () { /* run this sometime later */ } })

and "run" the code in the method later. It's a pain to handle (anonymous inner class), but it can be done.

Does Go have something that can facilitate a function/callback being passed in as a parameter?

This is the simplest way I can come with.

package main

import "fmt"

func main() {
    g := greeting
    getFunc(g)
}

func getFunc(f func()) {
    f()
}

func greeting() {
    fmt.Println("Hello")
}

Here is a simple example:

    package main

    import "fmt"

    func plusTwo() (func(v int) (int)) {
        return func(v int) (int) {
            return v+2
        }
    }

    func plusX(x int) (func(v int) (int)) {
       return func(v int) (int) {
           return v+x
       }
    }

    func main() {
        p := plusTwo()
        fmt.Printf("3+2: %d\n", p(3))

        px := plusX(3)
        fmt.Printf("3+3: %d\n", px(3))
    }

You can pass function as parameter to a Go function. Here is an example of passing function as parameter to another Go function:

package main

import "fmt"

type fn func(int) 

func myfn1(i int) {
    fmt.Printf("\ni is %v", i)
}
func myfn2(i int) {
    fmt.Printf("\ni is %v", i)
}
func test(f fn, val int) {
    f(val)
}
func main() {
    test(myfn1, 123)
    test(myfn2, 321)
}

You can try this out at: https://play.golang.org/p/9mAOUWGp0k

Here is the sample "Map" implementation in Go. Hope this helps!!

func square(num int) int {
    return num * num
}

func mapper(f func(int) int, alist []int) []int {
    var a = make([]int, len(alist), len(alist))
    for index, val := range alist {

        a[index] = f(val)
    }
    return a
}

func main() {
    alist := []int{4, 5, 6, 7}
    result := mapper(square, alist)
    fmt.Println(result)

}

You can also pass the function of a struct, like:

    package main
    // define struct
    type Apple struct {}
    
    // return apple's color
    func (Apple) GetColor() string {
         return "Red" 
    }
    
    func main () {
        // instantiate
        myApple := Apple{}
        
        // put the func in a variable
        theFunc := myApple.GetColor
        
        // execute the variable as a function
        color := theFunc()
    
        print(color)
    }

output will be "Red", check on the playground

I hope the below example will provide more clarity.

package main

type EmployeeManager struct{
    category            string
    city                string
    calculateSalary     func() int64
}


func NewEmployeeManager() (*EmployeeManager,error){

    return &EmployeeManager{
        category : "MANAGEMENT",
        city : "NY",
        calculateSalary: func() int64 {
            var calculatedSalary int64
            // some formula
            return calculatedSalary
        },
    },nil
}

func (self *EmployeeManager) emWithSalaryCalculation(){
    self.calculateSalary = func() int64 {
        var calculatedSalary int64
        // some new formula
        return calculatedSalary
    }
}

func updateEmployeeInfo(em EmployeeManager){
    // Some code
}

func processEmployee(){
    updateEmployeeInfo(struct {
        category        string
        city            string
        calculateSalary func() int64
    }{category: "", city: "", calculateSalary: func() int64 {
        var calculatedSalary int64
        // some new formula
        return calculatedSalary
    }})
}

Yes Go does accept first-class functions.

See the article "First Class Functions in Go" for useful links.