iOS 获取文本内容的高度

+(CGFloat)textHeight:(NSString *)str andW:(CGFloat)width andTextFont:(CGFloat)textFont{    CGRect frame = [str boundingRectWithSize:Size(width, CGFLOAT_MAX)                                     options:NSStringDrawingUsesLineFragmentOrigin                                  attributes:@{NSFontAttributeName : [UIFont systemFontOfSize:textFont]}                                     context:NULL];        return frame.size.height;}