objective c - perform velocity in sprite kit only one time by touch begin -

I want to touch the phantom once in velocity, do not do it after touching it once

  - Create (SKSpriteNode *) BOLDWALL LOCATION: (CPP) status {_d = [SKSpriteNode spriteNodeWithImageNamed: @ "d"]; _d.position = Status; _d.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize: _d.size]; _d.physicsBody.velocity = Velocity; - (zero) touch touch: (NSSET *) touches the event: (UIEvent *) Event {}