11.3 ��Ͷ��ԣ��μ��ת��ӿڱ��

һ��ӿ��͵ı�� varI �п��԰��κ��͵�ֵ��һ�ַ�ʽ�� ��̬ ��ͣ��ʱ�ڱ��д洢��ֵ��ʵ��͡��ִ�й��ж�̬��Ϳ��ܻ��ͬ��ǿ��Է��ӿڱ��͡�ͨ��ǿ��ʹ�� ��Ͷ�� ��ĳ��ʱ�� varI �Ƿ�� T ��ֵ��

    v := varI.(T)       // unchecked type assertion

varI��һ��ӿڱ����ᱨ��invalid type assertion: varI.(T) (non-interface type (type of varI) on left) ��

��Ͷ��Կ��Ч�ģ��Ȼ��ᾡ��ת��Ƿ��Ч��Ԥ��еĿ��ԡ��ת��ڳ��ʱʧ�ܻᵼ�´��ȫ�ķ�ʽ��ʹ��ʽ��Ͷ��ԣ�

if v, ok := varI.(T); ok {  // checked type assertion
    Process(v)
    return
}
// varI is not of type T

��ת��Ϸ��v �� varI ת�� T��ֵ��ok �� true�� v �� T ��ֵ��ok �� false��Ҳû��ʱ��

Ӧ��ʹ��ķ�ʽ��Ͷ����

��£��ǿ��ֻ�� if �в��һ�� ok ��ֵ��ʱʹ��µķ����ģ�

if _, ok := varI.(T); ok {
    // ...
}

TODO ??��In this form shadowing the variable varI by giving varI and v the same name is sometimes done.

ʾ�� 11.4 type_interfaces.go

package main

import (
	"fmt"
	"math"
)

type Square struct {
	side float32
}

type Circle struct {
	radius float32
}

type Shaper interface {
	Area() float32
}

func main() {
	var areaIntf Shaper
	sq1 := new(Square)
	sq1.side = 5

	areaIntf = sq1
	// Is Square the type of areaIntf?
	if t, ok := areaIntf.(*Square); ok {
		fmt.Printf("The type of areaIntf is: %T\n", t)
	}
	if u, ok := areaIntf.(*Circle); ok {
		fmt.Printf("The type of areaIntf is: %T\n", u)
	} else {
		fmt.Println("areaIntf does not contain a variable of type Circle")
	}
}

func (sq *Square) Area() float32 {
	return sq.side * sq.side
}

func (ci *Circle) Area() float32 {
	return ci.radius * ci.radius * math.Pi
}

��

The type of areaIntf is: *main.Square
areaIntf does not contain a variable of type Circle

��ж��һ�� Circle��Ҳʵ�� Shaper �ӿڡ� t, ok := areaIntf.(*Square); ok �� areaIntf ��Ƿ�һ�� 'Square' ��͵ı��ȷ��ģ�Ȼ��ǲ��Ƿ��һ�� 'Circle' ��͵ı��Ƿ񶨵ġ�

��ע

�� areaIntf.(*Square) �е� * �ţ��ᵼ�±��impossible type assertion: Square does not implement Shaper (Area method has pointer receiver)��

11.3.md 2.6 KB Verlauf Originalformat

11.3 ���Ͷ��ԣ���μ���ת���ӿڱ���������

11.3.md 2.6 KB

Verlauf Originalformat

11.3 ��Ͷ��ԣ��μ��ת��ӿڱ��