獲取系統默認字符串高度獲取如下:

- (CGFloat)getStringHeightWithText:(NSString *)text font:(UIFont *)font viewWidth:(CGFloat)width {
    // 設置文字屬性 要和label的一致
    NSDictionary *attrs = @{NSFontAttributeName :font};
    CGSize maxSize = CGSizeMake(width, MAXFLOAT);

    NSStringDrawingOptions options = NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading;

    // 計算文字占據的寬高
    CGSize size = [text boundingRectWithSize:maxSize options:options attributes:attrs context:nil].size;

   // 當你是把獲得的高度來布局控件的View的高度的時候.size轉化為ceilf(size.height)。
    return  ceilf(size.height);
}

獲取含有行間距的字符串高度：

- (CGFloat)getString:(NSString *)string lineSpacing:(CGFloat)lineSpacing font:(UIFont*)font width:(CGFloat)width {
    NSMutableParagraphStyle *paraStyle = [[NSMutableParagraphStyle alloc] init];
    paraStyle.lineSpacing = lineSpacing;
    NSDictionary *dic = @{ NSFontAttributeName:font, NSParagraphStyleAttributeName:paraStyle };
    CGSize size = [string boundingRectWithSize:CGSizeMake(width, MAXFLOAT) options: NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading attributes:dic context:nil].size;
    return  ceilf(size.height);
}