我想使用 Google Cloud Platform Datastore 進(jìn)行數(shù)據(jù)分頁，我在 GCP 的頁面 ( https://cloud.google.com/datastore/docs/concepts/queries )上找到了一個(gè)使用 Cursors 進(jìn)行分頁的示例，它可以正常工作絕對(duì)沒問題。Google 提供的示例對(duì)變量進(jìn)行了硬編碼var tasks []Task， var task Task我想創(chuàng)建一個(gè)可重用的函數(shù)，我可以在其中通過鍵入的參數(shù)將指針傳遞給結(jié)構(gòu)數(shù)組interface{}，并通過該函數(shù)填充該結(jié)構(gòu)。例如： type MyStruct1 struct { F1 string } type MyStruct2 struct { F1 int } func list(ctx context.Context, cursorStr string, data interface{}) { ... } func main() { mystruct1 := make([]MyStruct1, 0) list(ctx, "", &mystruct1) mystruct2 := make([]MyStruct2, 0) list(ctx, "", &mystruct2) }當(dāng)我需要在此函數(shù)中創(chuàng)建一個(gè)變量來存儲(chǔ)記錄，然后將其附加到作為指針傳遞的結(jié)構(gòu)數(shù)組時(shí)，我的問題就開始了。來自谷歌的例子func SnippetIterator_Cursor() { ctx := context.Background() client, _ := datastore.NewClient(ctx, "my-proj") cursorStr := "" // [START datastore_cursor_paging] const pageSize = 5 query := datastore.NewQuery("Tasks").Limit(pageSize) if cursorStr != "" { cursor, err := datastore.DecodeCursor(cursorStr) if err != nil { log.Fatalf("Bad cursor %q: %v", cursorStr, err) } query = query.Start(cursor) } // Read the tasks. var tasks []Task << THIS IS WHAT I WANT TO BE GENERIC var task Task. << THIS IS WHAT I WANT TO BE GENERIC it := client.Run(ctx, query) _, err := it.Next(&task) for err == nil { tasks = append(tasks, task) _, err = it.Next(&task) } if err != iterator.Done { log.Fatalf("Failed fetching results: %v", err) } // Get the cursor for the next page of results. nextCursor, err := it.Cursor() // [END datastore_cursor_paging] _ = err // Check the error. _ = nextCursor // Use nextCursor.String as the next page's token.}
1 回答
慕運(yùn)維8079593
TA貢獻(xiàn)1876條經(jīng)驗(yàn) 獲得超5個(gè)贊
使用反射包：
func list(ctx context.Context, kind string, dst interface{}, pageSize int, cursorStr string) string {
? ? client, _ := datastore.NewClient(ctx, "my-proj")
? ? query := datastore.NewQuery(kind).Limit(pageSize)
? ? if cursorStr != "" {
? ? ? ? cursor, err := datastore.DecodeCursor(cursorStr)
? ? ? ? if err != nil {
? ? ? ? ? ? log.Fatalf("Bad cursor %q: %v", cursorStr, err)
? ? ? ? }
? ? ? ? query = query.Start(cursor)
? ? }
? ? // Get reflect value for the result slice.
? ? results := reflect.ValueOf(dst).Elem()
? ? // Allocate new value of the slice element type.?
? ? // resultp is pointer to that value.
? ? resultp := reflect.New(results.Type().Elem())
? ? it := client.Run(ctx, query)
? ? _, err := it.Next(resultp.Interface())
? ? for err == nil {
? ? ? ? // Append last value to results
? ? ? ? results.Set(reflect.Append(results, resultp.Elem())
? ? ? ? _, err = it.Next(resultp.Interface())
? ? }
? ? if err != iterator.Done {
? ? ? ? log.Fatalf("Failed fetching results: %v", err)
? ? }
? ? // Get the cursor for the next page of results.
? ? nextCursor, err := it.Cursor()
? ? // [END datastore_cursor_paging]
? ? _ = err? ? ? ? // Check the error.
? ? _ = nextCursor // Use nextCursor.String as the next page's token.
}
使用指向目標(biāo)切片的指針調(diào)用函數(shù)：
var data []Tasks
cursor := list(ctx, "Tasks", &data, 10, "")
- 1 回答
- 0 關(guān)注
- 197 瀏覽
添加回答
舉報(bào)
0/150
提交
取消