Navigation-back button and/or Cancel button in upper-left corner of iOS data entry screen?

Question

I have an iOS screen that is usually used for data entry but is occasionally used to later view the data that's been entered.

For data entry, it seems like the iOS convention (e.g. stock email app) is to use a button (e.g. Cancel) in the upper-left and a Submit button in the upper-right.

But for data viewing (e.g. stock camera roll app), the convention is for the upper-left button to be a navigation button that looks like a backwards-pointing arrow.

For a screen which is sometimes viewing and sometimes editing, should I use a navigation button in the upper-left, a Cancel button in the upper-left, or should I change the button from navigation arrow button to a Cancel button after the user makes any changes on the screen?

Answer 1

• If your using the Navigation Bar, then the standard convention is to have the Back button on the Upper-Left hand corner.

• Toggling the button from Back to Cancel wont make sense at all, your just confusing the user. Even if he made changes and pressed Cancel, he would go back to the previous screen itself.

• Here is my take, have a Back button in the Upper-Left corner, and have an Edit button in the Upper-Right corner. On pressing Edit, change the buttons to Cancel in the Upper-Left and Submit in the Upper-Right on the Navigation Bar.

• Pressing Cancel or Submit would take him to a Navigation Bar on top where he again sees Back & Edit, the only difference being one would discard the changes and one would save them.

Update:

• Attaching a screenshot of the what i explained above.