A Tour of Go Interfaces

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An interface type is defined by a set of methods.

A value of interface type can hold any value that implements those methods.

Note: The code on the left fails to compile.

Vertex doesn't satisfy Abser because the Abs method is defined only on*Vertex, not Vertex.

package mainimport (
"fmt"
"math"
)
type Abser interface {
Abs() float64
} func main() {
var a Abser
f := MyFloat(-math.Sqrt2)
v := Vertex{, } a = f // a MyFloat implements Abser
a = &v // a *Vertex implements Abser // In the following line, v is a Vertex(not *Vertex)
// and does Not Implement Abser.
//a = v
fmt.Println(a.Abs())
} type MyFloat float64 func (f MyFloat) Abs() float64 {
if f < {
return float64(-f)
}
return float64(f)
} type Vertex struct {
X,Y float64
} func (v *Vertex) Abs() float64 {
return math.Sqrt(v.X*v.X + v.Y*v.Y)
}