点击图标大小至少为这么大：
Make it easy for people to interact with content and controls by giving each interactive element ample spacing. Give tappable controls a hit target of about 44 x 44 points.
设计登陆的时候不要强迫用户必须登陆，如果必须强迫登陆，请说明原因。（个人经验：如果强制绑定用微信登陆是会在审核的时候拒绝的）
Delay a login requirement for as long as possible. It’s best when users can navigate through much of your app and use some of its functionality without logging in. For example, App Store doesn’t ask users to log in until they decide to buy something. Users often abandon apps that force them to log in before they can do anything useful.
If users must log in, display in the login view a brief, friendly explanation that describes the reasons for the requirement and how it benefits users.
不要设计退出的设置
An iOS app never displays a Close or Quit option. People stop using an app when they switch to another app, return to the Home screen, or put their devices in sleep mode.
及时地保存数据
Save user data as soon as possible and as often as reasonable. Do this because an app in the background can be told to exit or terminate at any time.
手势
Tap To press or select a control or item.
Drag To scroll or pan—that is, move side to side.
To drag an element.
Flick To scroll or pan quickly.
Swipe With one finger, to return to the previous screen, to reveal the hidden view in a split view controller, or the Delete button in a table-view row.
With four fingers, to switch between apps on iPad.
Double tap To zoom in and center a block of content or an image.
To zoom out (if already zoomed in).
Pinch Pinch open to zoom in; pinch close to zoom out.
Touch and hold In editable or selectable text, to display a magnified view for cursor positioning.
Shake To initiate an undo or redo action.
按钮的背景边界非必要时不要设置边框
In a content area, add a button border or background only if necessary. Buttons in bars, action sheets, and alerts don’t need borders because users know that most of the items in these areas are interactive. In a content area, on the other hand, a button might need a border or a background to distinguish it from the rest of the content. For example, Music, Clock, Photos, and App Store use such buttons in a few specific contexts.
Text Should Always Be Legible
字体不能低于11point， 17 point是一个默认字体。 通常iphone 一个point有两个像素pixel。
Make sure all styles of a custom font are legible at different sizes. One way to do this is to emulate some of the ways iOS displays font styles at different text sizes. For example:
Text should never be smaller than 11 points, even when the user chooses the extra-small text size. For comparison, the body style uses a font size of 17 points at the large size, which is the default text-size setting.
In general, font size and leading values differ by one point per text-size setting. Exceptions to this are the two caption styles, which use the same font size, leading, and tracking at the extra-small, small, and medium settings.
At the smallest three text sizes, tracking values are relatively large; at the largest three text sizes, tracking values are relatively tight.
The headline and body styles use the same font size. To distinguish it from the body style, the headline style uses a heavier weight.
Text in a navigation controller uses the same font size that body style text uses for the large setting (specifically, 17 points).
Text always uses either regular or medium weight; it doesn’t use light or bold.
一般而言，通常系统的操作不要自定义图标，用系统的图标，如果只是单纯想要界面不同，那就用系统API设置系统控件的颜色和外观。
In general, avoid creating a custom UI element that performs a standard action. First, ask yourself why you’re creating a custom UI element that behaves exactly like a standard one. If you just want a custom look, consider changing the look of a standard element by using the UIKit appearance customization APIs or tint color. If you want a slightly different behavior, be sure to find out whether a standard element might do what you want when you adjust its properties and attributes. If you need completely custom behavior, it’s best to design a custom element that doesn’t look too similar to the standard ones.