Google Drive integration in iOS mobile app (Objective C)

We have an existing project where there is a module with file upload currently implemented. The flow is as below- 1. In a module, user is clicking on "Upload File" icon 2. An option menu opens to choose file from iCloud or Google Drive 3. If user chooses iCloud, he can browse his iCloud files(PDF,Doc,Docx,Txt) and choose one 4. The chosen file gets uploaded to server as multipart file along with other form data All above steps are implemented when user selects iCloud. We just need the Google Drive option to be implemented for point 3 above where user when chooses Google Drive, he can browse his Google Drive files and choose a file(PDF,Doc,Docx,Txt). The chosen file will then be uploaded to server using already implemented file upload utility(point 4) Notes: Any pop up, notification etc should match application's look and feel. Before starting project, you will sign an NDA with us. After development and complete testing, you should send a build via daiwi to us. After our testing, once we approve, you will commit the code in our git repository and provide us with a code walkthrough. Code should follow modular approach with best industry practices.