Integrating Facebook Login in iOS App – The Manual Way

Ref : https://medium.com/@jerrywang0420/ios-swift-3-facebook-%E7%99%BB%E5%85%A5-%E7%99%BB%E5%87%BA%E6%95%99%E5%AD%B8-sign-in-sign-out-9bb996157355

照著做就可以了...不難