dynamic select without knowing the table name

[chekaiyin]

I need a universal function to retrieve all records from tables.
Struct:

type Account struct {
	bun.BaseModel

	ID    int64  `bun:",pk"`
	Name  string `bun:",notnull"`
	Owner string `bun:",notnull"`
}

func (*Account) Codes() []interface{} {
	return []interface{}{
		Account{ID: 1, Name: "name1", Owner: "owner1"},
		Account{ID: 2, Name: "name2", Owner: "owner2"},
	}
}

type CodeTable interface {
	Codes() []interface{}
}

I would like to call the function this way:
loadCodeTable(db, (*Account)(nil))

in function loadCodeTable, it needs to retrieve all records and returning to a slice
it works with map:

var dbCodes []map[string]interface{}
err := db.NewSelect().Model(codeTable).Scan(context.Background(), &dbCodes)

but how can I retrieve all records to a slice of struct Account? I tried reflect, but no help.

Thanks!

[jhhom]

Hi @chekaiyin, if I understand correctly, you need a universal loadCodeTable that can be called on slices of any structs, not just Account struct.

The following is what I came up with, not sure if it solves your problem.

You can retrieve all records to the Account struct by simply passing a reference of the slice to the Scan function like so:

func loadCodeTable2(db *bun.DB, codeTable CodeTable) ([]Account, error) {
	accounts := make([]Account, 0)
	err := db.NewSelect().Model(codeTable).Scan(context.Background(), &accounts)
	return accounts, err
}

If you need the function to be universal across every type, not just for Account, you can use Golang generics.

func loadCodeTable[T any](db *bun.DB, codeTable CodeTable) ([]T, error) {
	data := make([]T, 0)
	err := db.NewSelect().Model(codeTable).Scan(context.Background(), &data)
	return data, err
}

You can then use the above generic function for different types of struct, not just for Account, to do so you just need to pass the type parameter when you call it:

data, err := loadCodeTable[Account](db, (*Account)(nil))

data2, err := loadCodeTable[Person](db, (*Person)(nil))

[chekaiyin]

thanks @jhhom it resolved the issue!