iOS如何计算字符串的长度

在给定宽度的情况下，控件如何根据字符串的长度自适应，版本为xocde5，主要代码如下

    NSString *str = @"字符串长度测试第二行字符串长度测试第二行字符串长度测试第二行字符串长度测试第二行";

    UIFont *font = [UIFont systemFontOfSize:15];

    NSArray *arry = [str componentsSeparatedByString:@" "];

    NSInteger width = 100;

    float height = 0;

    float sx = 0;

    for (NSString *str in arry) {

        NSString *t = str;

        if ([t isEqualToString:@""]) {

            t = @" ";

        }

        CGSize detailSize;

        NSDictionary *attrDic = [NSDictionary dictionaryWithObjectsAndKeys:font, NSFontAttributeName, nil];

        detailSize = [t boundingRectWithSize:CGSizeMake(width, 10000.0f) options:NSStringDrawingUsesLineFragmentOrigin attributes:attrDic context:nil].size;

        

        height += detailSize.height;

        sx = detailSize.width;

    }

    CGSize size1 = CGSizeMake(sx, height);