Pass an Interface as an argument to a function in Go (Golang)
example1/
|-- main.go
|-- go.mod
|-- monitor/
|-- monitor.go
This declares the module name example1 and specifies that this module is written in Go version 1.20.
Example
module example1
go 1.20
In this package, an interface Monitor is defined with a method Speed() that returns a float64. A struct Vehicle is also defined with two fields Distance and Time, representing the distance traveled and the time taken. The Vehicle type implements the Monitor interface by providing a method Speed(), which calculates and returns the speed of the vehicle.
Example
package monitor
type Monitor interface {
Speed() float64
}
type Vehicle struct {
Distance float64
Time float64
}
func (v Vehicle) Speed() float64 {
return v.Distance / v.Time
}
In the main package, you import the monitor package from the example1 module. A function PrintSpeed is defined to take a parameter m of the interface type monitor.Monitor, and it prints the speed calculated by calling the Speed() method on m.
In the main() function, a Vehicle instance s is created with Distance 2.6 and Time 4.1. Then, PrintSpeed is called with s as the argument, which, in turn, calls the Speed() method on s and prints the calculated speed.
Example
package main
import (
monitor "example1/monitor"
"fmt"
)
func PrintSpeed(m monitor.Monitor) {
fmt.Printf("Speed: %f\n", m.Speed())
}
func main() {
s := monitor.Vehicle{Distance: 2.6, Time: 4.1}
PrintSpeed(s)
}
-
The
Monitorinterface in themonitorpackage represents any type that can provide a speed measurement. -
The
Vehiclestruct in themonitorpackage implements this interface by providing aSpeed()method. -
In the
mainpackage, we have a functionPrintSpeedthat accepts any type that implements theMonitorinterface. We then create an instance ofVehicleand pass it to this function.
When the program is executed, it computes the speed of the Vehicle and prints the result using the PrintSpeed function from the main package.