GO语言面试系列:（九）golang强制类型转换示例（usafe包）

题目：

设计父结构体—员工。子结构体：工人,农民,教师,科学家(scientist),服务生。
（1）其中工人,农民,服务生只有基本工资。（10分）
（2）教师除基本工资外,还有课酬(元/天)。（10分）
（3）科学家除基本工资外,还有年终奖。（10分)
编写一个测试结构体,将各种类型的员工的全年工资打印出来。（10分)

代码示例：

package main

import (
    "fmt"
    "unsafe"
)

type Employee struct {
    //基本工资
    BaseWage float64
    eType    E_TYPE //员工类型
}

type E_TYPE string

const (
    WORKER    E_TYPE = "工人"
    FARMER           = "农民"
    TEACHER2         = "老师"
    SCIENTIST        = "科学家"
    WAITER           = "服务员"
)

type Worker struct {
    Employee
}

func (e *Employee) getYearBaseSalary() float64 {
    return 12 * e.BaseWage
}

func (e *Employee) PrintSalary() {
    fmt.Printf("%s全年工资：", e.eType)
    switch e.eType {
    case WORKER:
        fallthrough
    case FARMER:
        fallthrough
    case WAITER:
        fmt.Printf("%.2f\n", e.BaseWage)
    case TEACHER2:
        //下面使用unsafe包的Pointer将父类(Employee)实例转为子类(Teacher2)实例
        //将父类实例转为通用指针
        uP := unsafe.Pointer(e)
        //再转换为本地 Teacher2 结构体
        pT := (*Teacher2)(uP)
        //转换完毕，可以输出子类特有属性
        fmt.Println("测试-->老师的课酬是:", pT.ClassRemuneration)
        fmt.Printf("%.2f\n", e.getYearBaseSalary()+pT.ClassRemuneration)
    case SCIENTIST:
        uP := unsafe.Pointer(e)
        pT := (*Scientist)(uP)
        fmt.Printf("%.2f\n", e.getYearBaseSalary()+pT.YearEndBonus)
    default:
        fmt.Println("未能匹配到对应的员工类型")
    }

}

type Farmer struct {
    Employee
}

type Teacher2 struct {
    Employee
    //课酬 (元/天)
    ClassRemuneration float64
}

type Scientist struct {
    Employee
    //年终奖
    YearEndBonus float64
}

type Waiter struct {
    Employee
}

//----------------测试------------------------

func main() {
    //实例化工人
    var worker *Worker = &Worker{Employee: Employee{BaseWage: 120, eType: WORKER}}
    //实例化农民
    var farmer *Farmer = &Farmer{
        Employee: Employee{
            BaseWage: 150,
            eType:    FARMER,
        },
    }
    //实例化老师
    employee := &Employee{BaseWage: 250, eType: TEACHER2}
    var teacher2 *Teacher2 = &Teacher2{Employee: *employee}
    teacher2.ClassRemuneration = 500
    //实例化科学家
    var scientist *Scientist = &Scientist{
        Employee{BaseWage: 300, eType: SCIENTIST},
        200,
    }
    //实例化服务人员
    var waiter *Waiter = &Waiter{Employee: Employee{BaseWage: 150, eType: WAITER}}
    //测试输出
    worker.PrintSalary()
    farmer.PrintSalary()
    waiter.PrintSalary()
    teacher2.PrintSalary()
    scientist.PrintSalary()
}

运行结果：

---

从以上代码中可以看到，我们没有使用接口，给父类绑定一个方法PrintSalary，子类就都可以使用这个方法了，然后在该方法内对父类型强转成了子类型。

感谢作者：波涛澎湃
参考链接：https://www.jianshu.com/p/402c79820fa8?utm_campaign=studygolang.com&utm_medium=studygolang.com&utm_source=studygolang.com

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