1. 利用defer、recover来实现try...catch
func Try(fun func(), handler func(interface{})) {
defer func() {
if err := recover(); err != nil {
handler(err)
}
}()
fun()
}
func main() {
Try(func() {
panic("foo")
}, func(e interface{}) {
print(e)
})
}
2. 关于error的一个程序
error是一个类型，类似于string，error也可以定义自己的类型
package main
import "errors"
import "fmt"
// By convention, errors are the last return value and
// have type `error`, a built-in interface.
func f1(arg int) (int, error) {
if arg == 42 {
// `errors.New` constructs a basic `error` value
// with the given error message.
return -1, errors.New("can't work with 42")
}
// A nil value in the error position indicates that
// there was no error.
return arg + 3, nil
}
// It's possible to use custom types as `error`s by
// implementing the `Error()` method on them. Here's a
// variant on the example above that uses a custom type
// to explicitly represent an argument error.
type argError struct {
arg int
prob string
}
func (e *argError) Error() string {
return fmt.Sprintf("%d - %s", e.arg, e.prob)
}
func f2(arg int) (int, error) {
if arg == 42 {
// In this case we use `&argError` syntax to build
// a new struct, supplying values for the two
// fields `arg` and `prob`.
return -1, &argError{arg, "can't work with it"}
}
return arg + 3, nil
}
func main() {
// The two loops below test out each of our
// error-returning functions. Note that the use of an
// inline error check on the `if` line is a common
// idiom in Go code.
for _, i := range []int{7, 42} {
if r, e := f1(i); e != nil {
fmt.Println("f1 failed:", e)
} else {
fmt.Println("f1 worked:", r)
}
}
for _, i := range []int{7, 42} {
if r, e := f2(i); e != nil {
fmt.Println("f2 failed:", e)
} else {
fmt.Println("f2 worked:", r)
}
}
// If you want to programmatically use the data in
// a custom error, you'll need to get the error as an
// instance of the custom error type via type
// assertion.
_, e := f2(42)
if ae, ok := e.(*argError); ok {
fmt.Println(ae.arg)
fmt.Println(ae.prob)
}
}
3. timer和ticker都是可以停止的
package main
import (
"fmt"
"time"
)
func main() {
ticker := time.NewTicker(time.Millisecond * 500)
go func() {
for t := range ticker.C {
fmt.Println("ticker is at ", t)
}
}()
time.Sleep(time.Millisecond * 1500)
ticker.Stop()
fmt.Println("ticker stopped")
}
package main
import (
"fmt"
"time"
)
func main() {
timer1 := time.NewTimer(time.Second * 2)
<-timer1.C
fmt.Println("timer1 expired.")
timer2 := time.NewTimer(time.Second * 1)
go func() {
<-timer2.C
fmt.Println("timer2 expired.")
}()
ok := timer2.Stop()
if ok {
fmt.Println("timer2 stopped.")
}
}
4. 一个比较复杂的channel的例子
package main
import (
"fmt"
"math/rand"
"sync/atomic"
"time"
)
type readOp struct {
key int
resp chan int
}
type writeOp struct {
key int
val int
resp chan bool
}
func main() {
var ops int64 = 0
reads := make(chan *readOp)
writes := make(chan *writeOp)
go func() {
var state = make(map[int]int)
for {
select {
case read := <-reads:
read.resp <- state[read.key]
case write := <-writes:
state[write.key] = write.val
write.resp <- true
}
}
}()
for r := 0; r < 100; r++ {
go func() {
for {
read := &readOp{
key: rand.Intn(5),
resp: make(chan int)}
reads <- read
<-read.resp
atomic.AddInt64(&ops, 1)
}
}()
}
for w := 0; w < 10; w++ {
go func() {
for {
write := &writeOp{
key: rand.Intn(5),
val: rand.Intn(100),
resp: make(chan bool)}
writes <- write
<-write.resp
atomic.AddInt64(&ops, 1)
}
}()
}
time.Sleep(time.Second)
opsFinal := atomic.LoadInt64(&ops)
fmt.Println("ops:", opsFinal)
} 5. sort包封装了一些常用的排序方法，用起来还是很方便的
package main
import "fmt"
import "sort"
func main() {
strs := []string{"c", "a", "b"}
sort.Strings(strs)
fmt.Println("Strings:", strs)
ints := []int{7, 2, 4}
sort.Ints(ints)
fmt.Println("Ints: ", ints)
s := sort.IntsAreSorted(ints)
fmt.Println("Sorted: ", s)
}
6. slice的引用特性
package main
import (
"fmt"
)
func main() {
array := make([]int, 0, 3)
array = append(array, 1)
a := array
b := array
a = append(a, 2)
b = append(b, 3)
fmt.Println(a)
}
结果是什么呢？答案揭晓，输出是“[1 3]”。
就我的理解，slice 是一个{指向内存的指针，当前已有元素的长度，内存最大长度}的结构体，其中只有指向内存的指针一项是真正具有引用语义的域，另外两项都是每个 slice 自身的值。因此，对 slice 做赋值时，会出现两个 slice 指向同一块内存，但是又分别具有各自的元素长度和最大长度。程序里把 array 赋值给 a 和 b，所以 a 和 b 会同时指向 array 的内存，并各自保存一份当前元素长度 1 和最大长度 3。之后对 a 的追加操作，由于没有超出 a 的最大长度，因此只是把新值 2 追加到 a 指向的内存，并把 a 的“当前已有元素的长度”增加 1。之后对 b 进行追加操作时，因为 a 和 b 各自拥有各自的“当前已有元素的长度”，因此 b 的这个值依旧是 1，追加操作依旧写在 b 所指向内存的偏移为 1 的位置，也就复写了之前对 a 追加时写入的 2。
为了让 slice 具有引用语义，同时不增加 array 的实现负担，又不增加运行时的开销，似乎也只能忍受这个奇怪的语法了。
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