Golang例子：异常处理，Panic和Recover

Go provides us with the ability to regain control after panic has occurred. The built-in recover() function is called from within a defer to check if a panic happened.

The signature of the recover() function is as follows:

func recover() interface{}

The recover() function accepts no arguments and returns an empty interface{}. Capturing a panic in a deferred function is standard practice in Go.

package main

import (
	"errors"
	"fmt"
)

var result = 1

func chain(n int) {
	defer func() {
		if r := recover(); r != nil {
			fmt.Println(r)
		}
	}()

	if n == 0 {
		panic(errors.New("Cannot multiply a number by zero"))
	} else {
		result *= n
		fmt.Println("Output: ", result)
	}
}

func main() {
	chain(5)
	chain(2)
	chain(0)
	chain(8)
}

We have used r := recover() to detect any occurrence of panic in our program and assign the panic message to r. We call recover within an if statement and check to see if a non-nil value was found. We must call recover from within a defer because once a panic happens, only deferred functions are executed.

Running this code produces the following output:

Output:  5
Output:  10
Cannot multiply a number by zero
Output:  80

Golang例子：不用参数类型的可变参数函数

In the following example, the function signature accepts an arbitrary number of arguments of type slice.

package main

import (
	"fmt"
	"reflect"
)

func main() {
	variadicExample(1, "red", true, 10.5, []string{"foo", "bar", "baz"},
		map[string]int{"apple": 23, "tomato": 13})
}

func variadicExample(i ...interface{}) {
	for _, v := range i {
		fmt.Println(v, "--", reflect.ValueOf(v).Kind())
	}
}

1 -- int
red -- string
true -- bool
10.5 -- float64
[foo bar baz] -- slice
map[apple:23 tomato:13] -- map

Golang例子：可变参数 (Variadic Arguments)

package main

import "fmt"

func main() {
	variadicExample("red", "blue", "green", "yellow")
}

func variadicExample(s ...string) {
	fmt.Println(s[0])
	fmt.Println(s[3])
}

red
yellow

Golang例子： Map迭代输出

package main

import "fmt"

func main() {
    var employee = map[string]int{"Mark": 10, "Sandy": 20,
        "Rocky": 30, "Rajiv": 40, "Kate": 50}
    for key, element := range employee {
        fmt.Println("Key:", key, "=>", "Element:", element)
    }
}

Key: Rocky => Element: 30
Key: Rajiv => Element: 40
Key: Kate => Element: 50
Key: Mark => Element: 10
Key: Sandy => Element: 20