CGFloat height;
if (floor(NSFoundationVersionNumber) <=
NSFoundationVersionNumber_iOS_6_1) {
CGSize size = [label.text
sizeWithFont:label.font
constrainedToSize:CGSizeMake(label.frame.size.width,
FLT_MAX)
lineBreakMode:NSLineBreakByWordWrapping];
height = size.height;
} else {
NSStringDrawingContext *context = [[NSStringDrawingContext
alloc] init];
context.minimumScaleFactor = 1.0;
CGRect bounds = [label.text
boundingRectWithSize:CGSizeMake(label.frame.size.width,
FLT_MAX)
options:NSStringDrawingUsesLineFragmentOrigin
attributes:@{NSFontAttributeName:label.font}
context:context];
height = bounds.size.height;
}