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65 lines
1.3 KiB
Go
65 lines
1.3 KiB
Go
// _Interfaces_ are named collections of method
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// signatures.
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package main
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import (
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"fmt"
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"math"
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)
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// Here's a basic interface for geometric shapes.
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type geometry interface {
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area() float64
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perim() float64
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}
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// For our example we'll implement this interface on
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// `rect` and `circle` types.
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type rect struct {
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width, height float64
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}
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type circle struct {
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radius float64
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}
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// To implement an interface in Go, we just need to
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// implement all the methods in the interface. Here we
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// implement `geometry` on `rect`s.
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func (r rect) area() float64 {
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return r.width * r.height
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}
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func (r rect) perim() float64 {
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return 2*r.width + 2*r.height
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}
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// The implementation for `circle`s.
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func (c circle) area() float64 {
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return math.Pi * c.radius * c.radius
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}
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func (c circle) perim() float64 {
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return 2 * math.Pi * c.radius
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}
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// If a variable has an interface type, then we can call
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// methods that are in the named interface. Here's a
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// generic `measure` function taking advantage of this
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// to work on any `geometry`.
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func measure(g geometry) {
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fmt.Println(g)
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fmt.Println(g.area())
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fmt.Println(g.perim())
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}
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func main() {
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r := rect{width: 3, height: 4}
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c := circle{radius: 5}
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// The `circle` and `rect` struct types both
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// implement the `geometry` interface so we can use
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// instances of
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// these structs as arguments to `measure`.
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measure(r)
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measure(c)
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}
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