你不知道的自动布局

• autoresizingMask转换为自动约束

@interface UIView (UIConstraintBasedCompatibility) 

/* By default, the autoresizing mask on a view gives rise to constraints that fully determine 
 the view's position. This allows the auto layout system to track the frames of views whose 
 layout is controlled manually (through -setFrame:, for example).
 When you elect to position the view using auto layout by adding your own constraints, 
 you must set this property to NO. IB will do this for you.
 */
@property(nonatomic) BOOL translatesAutoresizingMaskIntoConstraints NS_AVAILABLE_IOS(6_0); // Default YES

/* constraint-based layout engages lazily when someone tries to use it (e.g., adds a constraint to a view).  If you do all of your constraint set up in -updateConstraints, you might never even receive updateConstraints if no one makes a constraint.  To fix this chicken and egg problem, override this method to return YES if your view needs the window to use constraint-based layout.  
 */
+ (BOOL)requiresConstraintBasedLayout NS_AVAILABLE_IOS(6_0);

@end

• 对于多行 UILabel 需要设置 preferredMaxLayoutWidth

// Support for constraint-based layout (auto layout)
// If nonzero, this is used when determining -intrinsicContentSize for multiline labels
@property(nonatomic) CGFloat preferredMaxLayoutWidth NS_AVAILABLE_IOS(6_0);

• 例子:

- (void)layoutSubviews {
    [super layoutSubviews];

    // for multiline UILabel's you need set the preferredMaxLayoutWidth
    // you need to do this after [super layoutSubviews] as the frames will have a value from Auto Layout at this point

    // stay tuned for new easier way todo this coming soon to Masonry

    CGFloat width = CGRectGetMinX(self.shortLabel.frame) - kPadding.left;
    width -= CGRectGetMinX(self.longLabel.frame);
    self.longLabel.preferredMaxLayoutWidth = width;

    // need to layoutSubviews again as frames need to recalculated with preferredLayoutWidth
    [super layoutSubviews];
}