一. 第一步：下載微信SDK
包的內容如下：

二. 工程配置：

1.配置URL scheme

2.加入白名單

3.倒入必要的SDK

三. 代碼：
好了，准備工作已經完成，下面開始寫代碼了
在AppDelegate里面：

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


        /** 微信 */

        WXApi.registerApp(WX_APPID, enableMTA: true)

        return true
}

func application(_ app: UIApplication, open url: URL, options: [UIApplicationOpenURLOptionsKey : Any] = [:]) -> Bool {

        WXApi.handleOpen(url, delegate: self)
        return true
    }

func application(_ application: UIApplication, open url: URL, sourceApplication: String?, annotation: Any) -> Bool {

        WXApi.handleOpen(url, delegate: self)
        return true
}

/** 微信會調 */
func onResp(_ resp: BaseResp!) {
        if resp.errCode == 0 && resp.type == 0 {//授權成功
            let response = resp as! SendAuthResp
            NotificationCenter.default.post(name: NSNotification.Name(rawValue: "WXLoginSuccessNotification"), object: response.code)
        }

}

在登錄界面：

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view,    typically from a nib.
    NotificationCenter.default.addObserver(self,selector: #selector(WXLoginSuccess(notification:)),name:   NSNotification.Name(rawValue: "WXLoginSuccessNotification"),object: nil)
}

//微信登錄
@IBAction func wxLoginBtnAction(_ sender: UIButton) {
    let urlStr = "weixin://"
    if UIApplication.shared.canOpenURL(URL.init(string: urlStr)!) {
        let red = SendAuthReq.init()
        red.scope = "snsapi_message,snsapi_userinfo,snsapi_friend,snsapi_contact"
        red.state = "\(arc4random()%100)"
        WXApi.send(red)
    }else{
        if #available(iOS 10.0, *) {
            UIApplication.shared.open(URL.init(string: "http://weixin.qq.com/r/qUQVDfDEVK0rrbRu9xG7")!, options: [:], completionHandler: nil)
        } else {
            // Fallback on earlier versions
            UIApplication.shared.openURL(URL.init(string: "http://weixin.qq.com/r/qUQVDfDEVK0rrbRu9xG7")!)
        }
    }
}

/**  微信通知  */
func WXLoginSuccess(notification:Notification) {

    let code = notification.object as! String
    let requestUrl = "https://api.weixin.qq.com/sns/oauth2/access_token?appid=\(WX_APPID)&secret=\(WX_APPSecret)&code=\(code)&grant_type=authorization_code"

    DispatchQueue.global().async {

        let requestURL: URL = URL.init(string: requestUrl)!
        let data = try? Data.init(contentsOf: requestURL, options: Data.ReadingOptions())

        DispatchQueue.main.async {
            let jsonResult = try! JSONSerialization.jsonObject(with: data!, options: JSONSerialization.ReadingOptions.mutableContainers) as! Dictionary<String,Any>
            let openid: String = jsonResult["openid"] as! String
            let access_token: String = jsonResult["access_token"] as! String
            self.getUserInfo(openid: openid, access_token: access_token)
        }
    }
}

/**  獲取用戶信息  */
func getUserInfo(openid:String,access_token:String) {
    let requestUrl = "https://api.weixin.qq.com/sns/userinfo?access_token=\(access_token)&openid=\(openid)"

    DispatchQueue.global().async {

        let requestURL: URL = URL.init(string: requestUrl)!
        let data = try? Data.init(contentsOf: requestURL, options: Data.ReadingOptions())

        DispatchQueue.main.async {
            let jsonResult = try! JSONSerialization.jsonObject(with: data!, options: JSONSerialization.ReadingOptions.mutableContainers) as! Dictionary<String,Any>
            print(jsonResult)

        }
    }
}

好了，微信用戶信息我們已經拿到了，下面只需要把這些信息發送給后台想怎么登就怎么登，哈哈哈！