排序具有公共字段的不同结构的最佳解决方案

Question

I have struct types like

type A struct {
    Name string
    CreatedAt time.Time
    ...
}

type B struct {
    Title string
    CreatedAt time.Time
    ...
}

type C struct {
    Message string
    CreatedAt time.Time
    ...
} 

And a generic slice

var result []interface{}

containing A, B and C elements (and more to come in the future)

I want to sort that slice by 'CreatedAt'.

What is the best solution ? I want to avoid checking types or casting...

Answer 1

The only way that you can have a slice containing both of these types anyway is that the slice contains some interface that is implemented by both types (including interface{}).

You will probably want to use the sort package and implement sort.Interface on your slice. The solution gets a little verbose, but makes good sense:

type Creation interface {
    GetCreated() time.Time
}

type A struct {
    Name      string
    CreatedAt time.Time
}

func (a *A) GetCreated() time.Time {
    return a.CreatedAt
}

func (a *A) String() string {
    return a.Name
}

type B struct {
    Title     string
    CreatedAt time.Time
}

func (b *B) GetCreated() time.Time {
    return b.CreatedAt
}

func (b *B) String() string {
    return b.Title
}

type AorB []Creation

func (x AorB) Len() int {
    return len(x)
}

func (x AorB) Less(i, j int) bool {
    // to change the sort order, use After instead of Before
    return x[i].GetCreated().Before(x[j].GetCreated())
}

func (x AorB) Swap(i, j int) {
    x[i], x[j] = x[j], x[i]
}

func main() {
    a := &A{"A", time.Now()}
    time.Sleep(1 * time.Second)
    b := &B{"B", time.Now()}
    aOrB := AorB{b, a}

    fmt.Println(aOrB)
    // [B A]

    sort.Stable(aOrB)

    fmt.Println(aOrB)
    // [A B]
}