iOS根据字符串计算UILabel的宽，高

UILabel的宽

+ (CGFloat)widthForText:(NSString *)text
{
//设置计算文本时字体的大小,以什么标准来计算
//kFontSize   12
NSDictionary *attrbute = @{NSFontAttributeName:[UIFont systemFontOfSize:14.0]};
//kPhotoCell_Width                300
return [text boundingRectWithSize:CGSizeMake((300 / 320.0) * kScreenWidth, 1000) options:NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading attributes:attrbute context:nil].size.width;
}

• UILabel的高

-(CGSize)sizeWithFont:(UIFont *)font Size:(CGSize)size{
CGSize resultSize;
//根据系统不同版本，调用不同方法
if ([[[UIDevice currentDevice] systemVersion] floatValue] < 7) {
//运行在7.0以前的设备
resultSize = [self sizeWithFont:font constrainedToSize:size lineBreakMode:NSLineBreakByWordWrapping];
}else{
NSDictionary *attributes = @{NSFontAttributeName : font};
resultSize = [self boundingRectWithSize:size options:NSStringDrawingUsesLineFragmentOrigin attributes:attributes context:nil].size;
}
//cell的整体高度
return resultSize ;
}