golang笔记之指针使用

月下独酌100 · · 544 次点击 · · 开始浏览    
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Choosing a value or pointer receiver

There are two reasons to use a pointer receiver.

  • The first is so that the method can modify the value that its receiver points to.

  • The second is to avoid copying the value on each method call. This can be more efficient if the receiver is a large struct, for example.

package main

import (
    "fmt"
    "math"
)

type Vertex struct {
    X, Y float64
}

func (v *Vertex) Scale(f float64) {
    v.X = v.X * f
    v.Y = v.Y * f
}

func (v *Vertex) Abs() float64 {
    return math.Sqrt(v.X*v.X + v.Y*v.Y)
}

func main() {
    v := &Vertex{3, 4}
    fmt.Printf("Before scaling: %+v, Abs: %v\n", v, v.Abs())
    v.Scale(5)
    fmt.Printf("After scaling: %+v, Abs: %v\n", v, v.Abs())
}

In this example, both Scale and Abs are with receiver type *Vertex, even though the Abs method needn't modify its receiver.

In general, all methods on a given type should have either value or pointer receivers, but not a mixture of both. (We'll see why over the next few pages.)

参考:
https://tour.golang.org/methods/8


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感谢作者:月下独酌100

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