FBSDKLog: Cannot use the Facebook app or Safari to authorize, fb(app id)

When i am using sample apps of Facebook for my iOS project then after clicking the login button it gets redirected to the safari page and i can login from there , but when i try to do the same with my app , it shows the above error. how to correct this error ? i followed every steps given in the Facebook documentation.

ps - i guess there is no need to install Facebook app in the simulator cause the sample apps are working perfectly fine .