Podfile missing and 'This app could not be installed'

My app ran successfully but I got 'This app could not be installed'. I tried the solutions on the internet but no help. Then I realize I lost my Podfile and cannot run 'pod update' in Terminal. Do you think the missing podfile is the cause of the app cannot being installed to Simulator? How to fix the missing podfile? I am thinking of running 'sudo gem install cocoapods' to install the podfile. But will it cause anything to my project. I will be appreciated if someone can give me the solutions. Thanks.