iphone - how to implement drop down menu -

I have to select a category from the drop down menu when I press a field ....

You can try using a UIActionSheet like this:

Then apply the representative methods like this:

  // A button is called when clicked. Scenes will be automatically rejected after this call return - (zero) Action sheet: (UIACffets *) Action sheet clicked Button ATindex: (NSITAZ) button index {Switch (button index) {Case X: // Choice option X break; ... Default: // Default Action Brake; }}