动态类型

// Content size category constants
UIContentSizeCategoryExtraSmall
UIContentSizeCategorySmall
UIContentSizeCategoryMedium
UIContentSizeCategoryLarge
UIContentSizeCategoryExtraLarge
UIContentSizeCategoryExtraExtraLarge
UIContentSizeCategoryExtraExtraExtraLarge

// Accessibility sizes
UIContentSizeCategoryAccessibilityMedium
UIContentSizeCategoryAccessibilityLarge
UIContentSizeCategoryAccessibilityExtraLarge
UIContentSizeCategoryAccessibilityExtraExtraLarge
UIContentSizeCategoryAccessibilityExtraExtraExtraLarge