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Golang学习笔记_20——error
Golang学习笔记_21——Reader
Golang学习笔记_22——Reader示例

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error补充

1. 基本错误处理

在Go中，函数通常返回两个值：一个是预期的结果，另一个是error类型的值。
如果函数执行过程中发生错误，error值将不为nil。

func divide(a, b float64) (float64, error) {if b == 0 {return 0, errors.New("division by zero")}return a / b, nil
}func error_demo_1() {// 调用 divide 函数进行除法运算result, err := divide(10, 0)if err != nil {// 处理错误println("Error:", err)} else {// 输出结果println("Result:", result)}
}

测试方法

func Test_error_demo_1(t *testing.T) {error_demo_1()
}

输出结果

=== RUN   Test_error_demo_1
Error: (0x105134bc8,0x1400009ef48)
--- PASS: Test_error_demo_1 (0.00s)
PASS

2. 自定义错误

自定义错误类型可以实现error接口，该接口仅包含一个Error方法，返回一个字符串。

// 自定义错误
type MyError2 struct {When stringwhat string
}func (e *MyError2) Error() string {return fmt.Sprintf("when: %s, what: %s", e.When, e.what)
}func testMyError() error {err := &MyError2{When: "now",what: "something wrong",}return err
}

测试方法

func Test_testMyError(t *testing.T) {if err := testMyError(); err != nil {fmt.Println(err)}
}

输出结果

=== RUN   Test_testMyError
when: now, what: something wrong
--- PASS: Test_testMyError (0.00s)
PASS

3. 错误类型判断

3.1 类型断言

// MyError2 是自定义错误类型func ErrorAssertDemo() error {err := &MyError2{When: "now",what: "something wrong",}return err
}func TestErrorAssertDemo() {err := ErrorAssertDemo()if specificErr := err.(*MyError2); specificErr != nil {fmt.Println("specificErr:", specificErr)} else {fmt.Println("normalErr:", err)}
}

测试方法

func Test_ErrorAssertDemo(t *testing.T) {TestErrorAssertDemo()
}

输出结果

=== RUN   Test_ErrorAssertDemo
specificErr: when: now, what: something wrong
--- PASS: Test_ErrorAssertDemo (0.00s)
PASS

3.2 类型选择

// 错误类型选择
// MyError2 是自定义错误类型
func ErrorTypeDemo1() error {return &MyError2{When: "now",what: "myError wrong",}
}func ErrorTypeDemo2() error {return errors.New("normal wrong")
}func switchErrorDemo(err error) {if err != nil {switch err1 := err.(type) {case *MyError2:fmt.Println("myError2:", err1)default:fmt.Println("normal:", err1)}}
}func TestErrorTypeDemo() {err1 := ErrorTypeDemo1()err2 := ErrorTypeDemo2()switchErrorDemo(err1)switchErrorDemo(err2)
}

测试方法

func Test_ErrorTypeDemo(t *testing.T) {TestErrorTypeDemo()
}

输出结果

=== RUN   Test_ErrorTypeDemo
myError2: when: now, what: myError wrong
normal: normal wrong
--- PASS: Test_ErrorTypeDemo (0.00s)
PASS

4. panic && recover

在Go中，panic用于表示一个不可恢复的运行时错误。当panic发生时，程序将停止正常执行，并开始逐级调用已注册的延迟函数（deferred functions），随后程序崩溃。
recover是一个内置函数，用于从panic中恢复。它只能在延迟函数中调用。在正常的执行路径中调用recover将返回nil。

// panic 和 recover
func myPanic() {panic("error happened")
}func safeRecover() {defer func() {if err := recover(); err != nil {fmt.Println("recover:", err)}}()myPanic()
}

测试方法

func Test_safeRecover(t *testing.T) {safeRecover()fmt.Println("after recover")}

输出结果

=== RUN   Test_safeRecover
recover: error happened
after recover
--- PASS: Test_safeRecover (0.00s)
PASS

源码

// error_demo_2.go 文件
package error_demoimport ("errors""fmt"
)func divide(a, b float64) (float64, error) {if b == 0 {return 0, errors.New("division by zero")}return a / b, nil
}func errorDemo1() {// 调用 divide 函数进行除法运算result, err := divide(10, 0)if err != nil {// 处理错误println("Error:", err)} else {// 输出结果println("Result:", result)}
}// 自定义错误
type MyError2 struct {When stringwhat string
}func (e *MyError2) Error() string {return fmt.Sprintf("when: %s, what: %s", e.When, e.what)
}func testMyError() error {err := &MyError2{When: "now",what: "something wrong",}return err
}func ErrorAssertDemo() error {err := &MyError2{When: "now",what: "something wrong",}return err
}func TestErrorAssertDemo() {err := ErrorAssertDemo()if specificErr := err.(*MyError2); specificErr != nil {fmt.Println("specificErr:", specificErr)} else {fmt.Println("normalErr:", err)}
}// 类型选择
func ErrorTypeDemo1() error {return &MyError2{When: "now",what: "myError wrong",}
}func ErrorTypeDemo2() error {return errors.New("normal wrong")
}func switchErrorDemo(err error) {if err != nil {switch err1 := err.(type) {case *MyError2:fmt.Println("myError2:", err1)default:fmt.Println("normal:", err1)}}
}func TestErrorTypeDemo() {err1 := ErrorTypeDemo1()err2 := ErrorTypeDemo2()switchErrorDemo(err1)switchErrorDemo(err2)
}// panic 和 recoverfunc myPanic() {panic("error happened")
}func safeRecover() {defer func() {if err := recover(); err != nil {fmt.Println("recover:", err)}}()myPanic()
}

// error_demo_2_test.go 文件
package error_demoimport ("fmt""testing"
)func Test_error_demo_1(t *testing.T) {errorDemo1()
}func Test_testMyError(t *testing.T) {if err := testMyError(); err != nil {fmt.Println(err)}
}func Test_ErrorAssertDemo(t *testing.T) {TestErrorAssertDemo()
}func Test_ErrorTypeDemo(t *testing.T) {TestErrorTypeDemo()
}func Test_safeRecover(t *testing.T) {safeRecover()fmt.Println("after recover")}