To Implement Facebook login in swift 3.0, we can use following steps.

1. install pod

 pod 'FacebookCore'
 pod 'FacebookLogin'

2.Register your app on the Facebook  developer account. After registration,Go to you info.plist, right click on it and select “Open As” and click “Source code”

3.Now add your fb id in “CFBundleURLSchemes” with “fb” prefix.

<dict>
 <key>CFBundleURLSchemes</key>
  <array>
     <string>fb + Your FB id</string>
  </array>
</dict> 

4.In your “LSApplicationQueriesSchemes” add these string

<key>LSApplicationQueriesSchemes</key>
  <array>
	<string>fbapi</string>
	<string>fb-messenger-api</string>
	<string>fbauth2</string>
  </array>

5.Now add your fb id in “FacebookAppID” key

<key>FacebookAppID</key>
   <string>your fb id</string>

6. After that, do following code in AppDelegate file of your project  -

i). Import facebookcore kit

import FacebookCore

ii). In you didFinishLaunchingWithOption function add following code

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        
        // Override point for customization after application launch.
        SDKApplicationDelegate.shared.application(application, didFinishLaunchingWithOptions: launchOptions)
        return true
    }

iii). Add this function in your app delegate

func application(_ app: UIApplication, open url: URL, options: [UIApplicationOpenURLOptionsKey : Any]) -> Bool {
        
        return SDKApplicationDelegate.shared.application(app, open: url, sourceApplication: (options[UIApplicationOpenURLOptionsKey.sourceApplication] as! String), annotation: options[UIApplicationOpenURLOptionsKey.annotation] as Any)

}

7. Now Create the Facebook manager Class which will manage the Facebook Sign In Process and write the following code in the class

import Foundation
import FacebookLogin
import FacebookCore

struct FBManager {
    
    // Login With Facebook
    func fbLogin(viewController:UIViewController, completion:@escaping (_ responseObject:AnyObject?, _ error:NSError?, _ success:Bool)->()) {
        let loginManager = LoginManager()
        loginManager.logOut()
        loginManager.logIn([.publicProfile, .email], viewController: viewController) { loginResult in

            switch loginResult{
                
            case .cancelled:
                completion(nil,nil,false)
                
            case .failed(let error):
                completion(nil,error as NSError?,false)
                 
            case .success(let grantedPermission,  _,  _):
                if grantedPermission.contains("email"){
                    print("Logged in!")

                    let params = ["fields" : "first_name, last_name, email, picture.type(large), id, name"]
                    let graphRequest = GraphRequest(graphPath: "me", parameters: params)
                    graphRequest.start {
                        (urlResponse, requestResult) in

                        switch requestResult {
                        case .success(let response):
                            print("Custom Graph Request Succeeded: \(response)")
                            print("My facebook id is \(response.dictionaryValue?["id"])")
                            completion(response.dictionaryValue as AnyObject?,nil,true)
                        
                        case .failed(let error):
                            print("Custom Graph Request Failed: \(error)")
                            completion(nil,error as NSError,false)
                        }
                    }
                }
                
            }
        }
    }
    
}

8. We can call this function from our view controller like this:

let fbManage = FBManager()
        fbManage.fbLogin(viewController: self, completion: { (result, error, status) in
            if status{
                //Logged In Successfully"
            }
            else{
                if error?.description != nil{
                    // Logged In Failed
                }
            }
        })