函数

package mainimport "fmt"func add(a int, b int) (int, error) {return a + b, nil
}func add2(a int, b int) (sum int, err error) {sum = a + berr = nilreturn sum, err
}// 参数数量任意
func add3(items ...int) (sum int) {for _, value := range items {sum += value}return sum
}//函数是一等公民，可以作为变量、参数// 闭包：可以随时归零，而且不需要全局变量
func autoIncrement() func() int {local := 0return func() int {local += 1return local}
}func main() {sum := add3(1, 2, 3)fmt.Println(sum)//闭包next := autoIncrement()for i := 0; i < 5; i++ {fmt.Print(next()) //1,2,3,4,5}fmt.Println()next2 := autoIncrement()for i := 0; i < 3; i++ {fmt.Print(next2()) //1,2,3}
}

defer

package mainimport ("fmt""sync"
)func deferReturn() (ret int) {defer func() {ret++}()return 10
}func main() {var mu sync.Mutexmu.Lock()defer mu.Unlock() //defer语句在return之前才执行//defer执行的顺序为栈的顺序，LIFOdefer fmt.Println("1")defer fmt.Println("2")ret := deferReturn()fmt.Println(ret)//11，defer有能力改变返回值
}

panic、recover

package mainimport "fmt"func main() {defer func() {r := recover()if r != nil {fmt.Println("recover!!!")//捕获panic}}()panic("panic!!!") //直接导致程序退出fmt.Println("1")
}

结构体

package mainimport "fmt"type Person struct {name    stringage     intaddress stringheight  float32
}func (p Person) print() {fmt.Printf("name:%s, age:%d", p.name, p.age)fmt.Println()
}type Student struct {p     Personscore float32
}type Student2 struct {Personscore float32
}func main() {type myInt2 = int //类型别名type myInt int    //自定义类型，不可加法，可扩展//初始化p1 := Person{"neo", 18, "mooc", 1.80}p2 := Person{name:    "harry",address: "beijing",}var p3 Personp3.age = 20p3.print()//匿名结构体：一次性address := struct {province stringcity     string}{province: "beijing1",city:     "beijing2",}fmt.Println(address)//结构数组pp3 := []Person{{name: "potter"},{name: "peter"},}fmt.Println(p1)fmt.Println(p2)fmt.Println(pp3)//嵌套结构体s := Student{Person{name: "neo", age: 18}, 99}s.p.height = 1.80s1 := Student{}s1.p.name = "neo"s2 := Student2{}s2.name = "neo"
}

指针

package mainimport "fmt"type Person2 struct {name string
}func main() {po := &Person2{name: "neo",}//以下在go中等效po.name = "leo"(*po).name = "neo"//初始化var pp = new(Person2)fmt.Println(pp.name)//nil的用法var m1 map[string]stringvar m2 = make(map[string]string, 0)//m1["name"] = "harry"  //报错m2["name"] = "potter" //不报错，建议用makefor key, value := range m1 {fmt.Println(key, value)}for key, value := range m2 {fmt.Println(key, value)}
}

interface

定义

package mainimport "fmt"// 接口定义
type Duck interface {Gaga()Walk()Swim()
}// 自定义类用于接口实现
type pskDuck struct {legs int
}func (pd *pskDuck) Gaga() {fmt.Println("Gaga")
}func (pd *pskDuck) Walk() {fmt.Println("walking")
}func (pd *pskDuck) Swim() {fmt.Println("swim")
}func main() {var d Duck = &pskDuck{}d.Walk()
}

多接口

package mainimport "fmt"type MyWriter interface {Write(string) error
}
type MyCloser interface {Close() error
}type fileWriter struct {filepath string
}
type databaseWriter struct {host stringport string
}
type writeCloser struct {MyWriter
}func (fw *fileWriter) Write(string) error {fmt.Println("write string to error")return nil
}
func (dw *databaseWriter) Write(string) error {fmt.Println("write string to database")return nil
}
func (wc *writeCloser) Close() error {fmt.Println("close")return nil
}func main() {var mw MyWriter = &writeCloser{&databaseWriter{},}mw.Write("harry")
}

断言

package mainimport ("fmt""strings"
)func add(a, b interface{}) interface{} {switch a.(type) {`package mainimport "fmt"type MyInterWriter interface {Write(string)
}
type MyInterReader interface {Read() string
}
type MyReadWriter interface {MyInterReaderMyInterWriterReadWrite()
}
type SreadWriter struct {
}func (s *SreadWriter) Read() string {fmt.Println("Read")return ""
}func (s *SreadWriter) Write(s2 string) {fmt.Println("Write")
}func (s *SreadWriter) ReadWrite() {fmt.Println("ReadWrite")
}func main() {var mrw MyReadWriter = &SreadWriter{}mrw.Read()
}
`case int:ai, _ := a.(int)bi, _ := b.(int)return ai + bicase float64:af, _ := a.(float64)bf, _ := b.(float64)return af + bfcase string:as, _ := a.(string)bs, _ := b.(string)return as + bsdefault:panic("not supported type")}
}func main() {re := add("hello", "world")res, _ := re.(string)strings.Split(res, " ")fmt.Println(re)
}

嵌套接口