When Yasuo moves to a battlefield using Ride the Wind during a showdown, does he trigger his 'when I attack' ability, or is he classified as a defending unit?

Ruling: Yasuo will not trigger his "when I attack" ability because he gains the defender designation, not the attacker designation, when moved to a battlefield that is already being contested.

Nuances:

• Units gain attacker or defender designation based on when they arrive at the battlefield, not based on which player is the turn player
• The unit that moves to the battlefield last gets the defender designation in a showdown