Go到数据存储的接口，两种实现

Question

Please see this repo. I'm trying to create an interface to a datastore. Reason: I don't want to be dependent on a real postgres db while developing, but I want to use an in-memory-implementation during dev.

This works, as long as I create the instances in my main(). For example: db := store.NewMemoryDB() or db := store.NewDB().

But now I want to create an instance based on a boolean. So I created a function GetDatastore(bool) in the store package. This works for the postgres implementation, but not for the in-memory. I get the following error: cannot use NewMemoryDB() (type *MockDB) as type *DB in assignment. Now I really don't know how to solve this. Can someone please give me a hint? How do I make the in-memory one *DB-compatible?

Answer 1

The return type of GetDatastore is the concrete type *DB, and *MockDB is not *DB which is why you get that error. What you want instead is to return the interface type Datastore, which both *DB and *MockDB implement.