Golang常用内置接口及自定义接口实践

type MyError struct {
    Msg string
}

func (e *MyError) Error() string {
    return "自定义错误：" + e.Msg
}

// 使用
err := &MyError{Msg: "文件不存在"}
if err != nil {
    log.Println(err.Error())
}

type Person struct {
    Name string
    Age  int
}

func (p Person) String() string {
    return fmt.Sprintf("%s (%d岁)", p.Name, p.Age)
}

// 输出：张三 (25岁)
fmt.Println(Person{Name: "张三", Age: 25})

var r io.Reader = strings.NewReader("hello")
var w io.Writer = os.Stdout
io.Copy(w, r) // 将字符串输出到标准输出

type Storage interface {
    Save(key string, value []byte) error
    Load(key string) ([]byte, error)
    Delete(key string) error
}

type MemoryStorage struct {
    data map[string][]byte
}

func NewMemoryStorage() *MemoryStorage {
    return &MemoryStorage{data: make(map[string][]byte)}
}

func (m *MemoryStorage) Save(key string, value []byte) error {
    m.data[key] = value
    return nil
}

func (m *MemoryStorage) Load(key string) ([]byte, error) {
    data, ok := m.data[key]
    if !ok {
        return nil, fmt.Errorf("键 %s 不存在", key)
    }
    return data, nil
}

func (m *MemoryStorage) Delete(key string) error {
    delete(m.data, key)
    return nil
}

type DataService struct {
    store Storage
}

func NewDataService(store Storage) *DataService {
    return &DataService{store: store}
}

func (s *DataService) SetUser(id string, data []byte) error {
    return s.store.Save("user:"+id, data)
}

func (s *DataService) GetUser(id string) ([]byte, error) {
    return s.store.Load("user:" + id)
}

svc := NewDataService(NewMemoryStorage())
svc.SetUser("1001", []byte(`{"name":"李四"}`))