The 24-year-old rapper is thrilled to be dating the 'Dangerous Woman' hitmaker but insists the pair are "very good friends first and foremost".
He told PEOPLE magazine: "I wrote that love song before I saw her. We're very good friends first and foremost. We made that song and started becoming close again. It's very dope and I like how that worked out.
"It was great. There was no awkwardness or weirdness, it was how it always was. Just both of us older, more mature and more sure of ourselves. When we first recorded together we were young and figuring it out, which we still are, but now seeing her growth and my growth - it's great.
"We hung out for a long time and everything just happened organically. We love making music together - we do that always. But she's my best friend in the world."
Despite enjoying a romance with Mac, Ariana previously insisted she finds it hard to get a date.
She said: "I think men approach me less now I'm famous, but then I hardly ever go out any more. I'm not pretending I have great break-up advice. It's hard. It's nice to have someone that makes you happy, but it's nice to be happy on your own as well."
However, the 'Into You' beauty is glad to have her "amazing friends and family" around her to keep her grounded.
She added: "I'm so lucky to be surrounded by amazing friends and family. I love having them around me. They keep it real and help me stay grounded. Family is everything to me, especially my nonna. I try not to pay attention to what people say about my body because I think you could go crazy listening to everything. I try to focus on the positives - my fans help me feel good too."