The Hollywood stars have been dating for well over a year, after meeting on the set of The Place Beyond the Pines.
They are regularly seen enjoying dates together and have made reference to each other in public, but aren't overly open about their relationship.
It's been claimed things work well as they are both so relaxed with each other.
"[Ryan is] an incredibly sweet boyfriend," a source close to the actor told People magazine. "They get along so well because she's not needy or smothering. They just work."
Ryan apparently finds it easy to make new friends because he is so open and honest. The star also likes having fun and recently took Eva on a date to Disneyland in California.
"Women love him because he's just kooky," the insider claimed. "He's definitely in touch with his childlike side."
Earlier this week, the actor attended the Hollywood premiere of his new movie Gangster Squad with his mother Donna. It seems his family have also bonded well with his girlfriend, as Donna happily told reporters she had delved into Eva's wardrobe to get a suitable outfit for the occasion.
The actress' mom is also thought to be a fan of her beau and was heard gushing over him during a meal out last year.
“As she was leaving, Eva’s mom was hugging and kissing Ryan. She loves him!” a source said at the time.