swift - SpriteKit Enemy colliding with each other -

i have enemies on stage in sks , i'm setting in code bellow

enemy = self.childnodewithname("enemy")! enemy.physicsbody?.categorybitmask = collidertypes.enemy.rawvalue enemy.physicsbody?.contacttestbitmask = collidertypes.player.rawvalue enemy.physicsbody?.collisionbitmask = collidertypes.player.rawvalue | collidertypes.ground.rawvalue 

where:

enum collidertypes: uint32{     case none = 0     case = 0xffffffff     case ground = 0b001     case player = 0b010     case enemy  = 0b100 } 

i explicitly declare want enemy contact ground , player, colliding each other. 1 walking slower "drag" 1 walking faster.

any ideas doing wrong?