Where to catch diglett in ruby?

Diglett is not available for capture in Pokémon Ruby you would have to trade with another trainer in order to receive one or you would have to use your Pokémon FireRed or Pokémon LeafGreen in order to catch Diglett in the Diglett Cave and then you would have to take it to the Pokémon Center in order to trade it over to your Pokémon Ruby game in order for Pokémon Ruby to receive Diglett.