Functions

Signature

The signature of a function is as following:

func functionName (parameters)(return values){
    <LOGIC>
}

Parameters

To pass a single parameter:

func helloWorld(param1 string) {
    fmt.Println(param1)

}

Pass two parameters:

func helloWorld(param1 string, param2 string) {
    fmt.Println(param1)
    fmt.Println(param1)
}

If the parameters are the same type they can be declared once:

func helloWorld(param1, param2 string) {
    fmt.Println(param1)
    fmt.Println(param1)
}

Variadic parameters uses an ellipsis operator converts the parameters into a collection of strings. The following example demonstrates param1 being converted to a slice:

func helloWorld(param1 ...string) {
    for _, n:= range param1 {
        fmt.Println(n)
    }
}

However, the caller of this function can pass in a single parameter at a time separated by commas multiple.

Important

Variadic parameters can only be used once in a function and must be the last parameter defined.

Values and pointers

When passing values into a function it is a copy of the value, so any manipulation done inside a function stays inside that function until the function exits. The original variable is unchanged in the main code flow.

In contrast, we can define a pointer, in which the opposite is true. Manipulation of a value inside a function WILL effect the global value in the code.

For example:

fun main(){
    param1, param2 := "foo", "bar"

    fmt.Println(param1)
    fmt.Println(param2)

    myFunction(param1 string, param2 *string)

    fmt.Println(param1)
    fmt.Println(param2)
}

func myFunction(param1 string, param2 *string) {
    param1 = "hello"
    *param2 = "world"
}

Tip

Only use pointers to share memory, else use standard values.

Return Values

Return a single value:

func main() {
    result := addNumbers(1, 2)
    fmt.Println(result)
}

func addNumbers(num1, num2 int) int {
    return num1 + num2
}

Return multiple values:

func main() {
    result, ok := divideNumbers(1, 2)
    if ok {
        fmt.Println(result)
    } 
}

fun divideNumbers(num1, num2 int) (int, bool) {
    if num2 == 0 {
        return 0, false
    }
    return num1 / num2, true
}

Named return values (rarely used):

func main() {
    result, ok := divideNumbers(1, 2)
    if ok {
        fmt.Println(result)
    } 
}

func divideNumbers(num1, num2 int) (result int, ok bool) {
    if num2 == 0 {
        return 
    }
    result = num1 / num2
    ok = true
    return
}