Accept interfaces, return structs

[zostay]

The various Database methods currently return interfaces rather than structs, but Golang best practice indicates that returning structs is best. Consider the following situation where I want to wrap the database with a special Pinger in cases where I can use that to help determine the health of the connection. (Unrelated, I am having some weird connectivity issues with memcached and I'm working on trying to determine why using code similar to this.)

type Pingable interface {
    Ping() error
}

type MCPinger struct {
    *server.Memcached
}

func (p *MCPinger) Ping() error {
    return p.Memcached.Client.Ping()
}

If NewMemcached() returned *server.Memcached as convention suggests it should, the code to initialize the MCPinger would read:

var p Pingable = &Pinger{server.NewMemcached(connectString)}

However, right now this code would instead read something like this:

db := server.NewMemcached(connectString)
mdb, ok := db.(*server.Memcached)
if !ok {
    panic("NewMemcached() returns a different object than expected.")
}
var p Pingable = &Pinger{mdb}

Both the memcached and redis databases are implemented this way. The fix is just to change the return type of each New*() function to return the pointer to the struct it constructs rather than the interface.

[zostay]

(And yes I realize I could save myself the if !ok ... panic bit if I skipped the , ok in the type conversion, but in my real code I'm not panicking, but returning an error to be logged and then panicking some place higher up the call frame stack.)

[jhaals]

Hi @zostay! Yes I'd say you're right on that point and I think it make sense to update that. Would you be willing to contribute that suggestion?

I'm currently adding my spare cycles on a reimplementation of the service in typescript and nextjs to both cleanup and make it easier for users to customise as the current react app is not that easy to extend.