如何在iPhone应用程序中处理身份验证

I'm currently developing my first native iPhone app (though I have many years of experience as a web developer). I'm having some difficulty understanding the best way to handle login and I'm looking for some advice on the best way to go about it. The more I think about all the things that can go wrong during login, the more my brain wants to jump out of my head. I'm getting really frustrated with this and could really use some advice from some more experienced iPhone developers. Thanks in advance for your help.I'm currently developing my first native iPhone