面试题笔试题学习日记——golang（7.26-1）

golang基础

协程池实现

import "sync"

type Woker interface {
	Work()
}

type Pool struct {
	work chan Worker
	wg sync.WaitGroup
} 

func NewPool(maxRoutine int) *Pool {
	p := Pool{
		work: make(chan Worker)
	}
	p.wg.Add(maxRoutine)
	for i:=0;i<maxRoutine;++i {
		go func(){
			for v := range work {
				v.Work()
			}
			p.wg.Done()
		}()
	}
	return &p
}

//提交工作到池子
func (p *Pool) Run(w Worker) {
	p.work <- w
}

//关闭池子
func (p *Pool) Close() {
	close(p.work)
	p.wg.Wait()
}

go类似多态实现

package main

import "fmt"

type AnimalIF interface {
    Sleep()
    Age() int
    Type() string
}
type Animal struct {
    MaxAge int
}

/*=======================================================*/

type Cat struct {
    Animal Animal
}

func (this *Cat) Sleep() {
    fmt.Println("Cat need sleep")
}
func (this *Cat) Age() int {
    return this.Animal.MaxAge
}
func (this *Cat) Type() string {
    return "Cat"
}

/*=======================================================*/

type Dog struct {
    Animal Animal
}

func (this *Dog) Sleep() {
    fmt.Println("Dog need sleep")
}
func (this *Dog) Age() int {
    return this.Animal.MaxAge
}
func (this *Dog) Type() string {
    return "Dog"
}

/*=======================================================*/

func Factory(name string) AnimalIF {
    switch name {
    case "dog":
        return &Dog{Animal{MaxAge: 20}}
    case "cat":
        return &Cat{Animal{MaxAge: 10}}
    default:
        panic("No such animal")
    }
}

/*======================================================*/

func main() {
    animal := Factory("dog")
    animal.Sleep()
    fmt.Printf("%s max age is: %d", animal.Type(), animal.Age())
}

panic和err的区别

处理错误并且在函数发生错误的地方给用户返回错误信息：照这样处理就算真的出了问题，你的程序也能继续运行并且通知给用户。
panic and recover是用来处理真正的异常（无法预测的错误）而不是普通的错误。
当发生像数组下标越界或类型断言失败这样的运行错误时，Go运行时会触发运行时panic，伴随着程序的崩溃抛出一个runtime.Error接口类型的值。这个错误值有个RuntimeError()方法用于区别普通错误。

go语言实现单例模式

双重检验枷锁

type Singleton struct{
}

var ins *Singleton
var mutex sync.Mutex
func GetIns() *Singleton{
	if ins == nil {
		mutex.Lock()
		if ins == nil {
			ins = &Singleton{}
		}
		mutex.Unlock()
	}
	return ins
}

sync.Once实现

type Singleton struct{}

var ins *Singleton
var once sync.Once

func GetIns() *Singleton {
	once.Do(func() {
		ins = &Singleton{}
	})
	return ins
}

go实现简单工厂

package main
import (
    "fmt"
)
type Op interface {
    getName() string
}
type A struct {
}
type B struct {
}
type Factory struct {
}
func (a *A) getName() string {
    return "A"
}
func (b *B) getName() string {
    return "B"
}
func (f *Factory) create(name string) Op {
    switch name {
    case `a`:
        return new(A)
    case `b`:
        return new(B)
    default:
        panic(`name not exists`)
    }
    return nil
}

25、26号面试题知识来源https://blog.csdn.net/littleflypig/article/details/98628692