Shows how to implement a multiline UILabel with Auto Layout. It will dynamically resize to fit whatever horizontal constraints you apply.

AutoLayoutLabel

@interface AutoLayoutLabel : UILabel

@end

@implementation AutoLayoutLabel
{
    CGFloat overrideWidth;
}

- (id)init
{
    if ((self = [super init])) {
        overrideWidth = 0.0f;
        self.numberOfLines = 0;
        self.lineBreakMode = NSLineBreakByWordWrapping;
    }
    return self;
}

- (void)layoutSubviews
{
    [super layoutSubviews];
    
    // Fit the label to it's contents on rotation or text change
    // http://stackoverflow.com/questions/15927086/uilabel-sizetofit-and-constraints
    if (self.preferredMaxLayoutWidth != [self alignmentRectForFrame:self.frame].size.width) {
        self.preferredMaxLayoutWidth = [self alignmentRectForFrame:self.frame].size.width;
        [self.superview setNeedsLayout];
    }
}

@end

It seems that overrideWidth is not used anywhere