在两个不同的结构上调用相同的函数

Question

I've got two functions that accept different pointers pointing to different structs, but the structs have the same underlying function.

func Save(db *sql.DB) error {
  db.Prepare(query)
}

func TxSave(tx *sql.Tx) error {
  tx.Prepare(query)
}

I don't want to have to make changes in both functions when I need to extend this function in the future. How do I adhere to DRYness in golang with this scenario?

Answer 1

Create an interface such as:

type SQLRunner interface{
    Prepare(query string) (*sql.Stmt, error)
    PrepareContext(ctx context.Context, query string) (*sql.Stmt, error)
    Query(query string, args ...interface{}) (*Rows, error)
    QueryContext(ctx context.Context, query string, args ...interface{}) (*sql.Rows, error)
    // add as many method shared by both sql.Tx qnd sql.DB
    // ...
} 

And then create a single method taking that interface:

func Save(s SQLRunner) error {
    s.Prepare()
}

In go interface implementation is implicit, so you just have to pass *sql.Tx or *sql.DB to the save function:

Save(tx)
Save(db)

Here a good blog post about interfaces in go:http://jordanorelli.com/post/32665860244/how-to-use-interfaces-in-go