如何使用iOS上的Dropbox API成功登录？

pod 'Dropbox-SDK'

github "dropbox/dropbox-sdk-obj-c"

<key>CFBundleURLTypes</key><array>
  <dict>
    <key>CFBundleURLSchemes</key>
   <array>
     <string>db-APP_KEY</string>
    </array>
  </dict>
</array>

import DropboxSDK

let session = DBSession(appKey: "APP_KEY", appSecret: "APP_SECRET", root: kDBRootAppFolder)

DBSession.sharedSession().linkFromController(self) { (session, error) in
  if let session = session {
    // 登录成功
  } else if let error = error {
    // 登录失败
  }
}

let client = DBRestClient(session: session)
client.loadMetadata("/", intoPath: "/", withCompletion: { (metadata, error) in
  if let metadata = metadata {
    // 处理文件和文件夹
  } else if let error = error {
    // 处理错误
  }
})