NSString（或者说是UILabel）加入 “行间距” 之后的 “高度”计算

一、首先，写一个工具类（NSString的分类，增加两个功能，计算高度宽度）

#import "NSString+Extension.h"

@implementation NSString (Extension)

#pragma mark -根据宽度，字号来计算字符串的高度
- (float) heightWithFont: (UIFont *) font withinWidth: (float) width{
    CGRect textRect = [self boundingRectWithSize:CGSizeMake(width, MAXFLOAT)
                                         options:NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading
                                      attributes:@{NSFontAttributeName:font}
                                         context:nil];
    return ceil(textRect.size.height);
}

#pragma mark -根据字号来计算字符串的宽度
- (float) widthWithFont: (UIFont *) font{
    CGRect textRect = [self boundingRectWithSize:CGSizeMake(MAXFLOAT, font.pointSize)                 options:NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading
                                      attributes:@{NSFontAttributeName:font}
                                         context:nil];
    return ceil(textRect.size.width);
}

二、为了适配不同系统，字体字号作如下封装：

/*
 *  自定义字号大小
 */
-(UIFont *)jyeFontWithName:(NSString *)name size:(CGFloat)size{
    UIFont * font = nil;
    if([[[UIDevice currentDevice] systemVersion] floatValue] >= 9){
        font = [UIFont fontWithName:name size:size];
    }else{

        if([name rangeOfString:@"Medium"].location == NSNotFound){
            font = [UIFont systemFontOfSize:size];
        }else{
            font = [UIFont boldSystemFontOfSize:size];
        }
    }
    return font;
}

三、在需要计算字符串高度宽度的类中，做如下处理：

　　　

        NSString *string = @"今日营养配餐提供热量1800千卡，需要饮食之外额外补充钙10mg，铁20mg，锌9.5mg，叶酸200μgDFE，维生素D 10ug，维生素B1 1.2mg，维生素B2 1.2mg。";

        UIFont *font = [self jyeFontWithName:@"PingFangSC-Regular" size:13];//需要与UILabel的text保持一致

        CGFloat oneRowHeight = [@"test" sizeWithAttributes:@{NSFontAttributeName:font}].height;//test  只是随便取得一个字符串，只要不超过一行就可以

        CGFloat textHeight = [string heightWithFont:font withinWidth:self.frame.size.width-30];

        CGFloat rows = textHeight/oneRowHeight;

        CGFloat realHeight = (rows *ceilf(oneRowHeight)) +(rows - 1)* LineSpace;//行间距 为4

       //realHeight  就是字符串的高度啦，此时你就可以根据交互设计图编写相应的UILabel的frame啦

四、UILabel 设置行间距

        

       UILabel * hotLabel = [[UILabel alloc]init];
        hotLabel.frame = CGRectMake(15, 20, sectionView.frame.size.width - 30, realHeight);
        hotLabel.textColor = JYEColor(163, 165, 173);
        hotLabel.numberOfLines = 0;
        hotLabel.font = [self jyeFontWithName:@"PingFangSC-Regular" size:13];

        NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithString:string];
        NSRange range = [string rangeOfString:@"今日营养配餐"];
        [attributedString addAttribute:NSForegroundColorAttributeName value:JYEColor(72, 75, 91) range:range];
        [attributedString addAttribute:NSFontAttributeName value:[self jyeFontWithName:@"PingFangSC-Medium" size:13] range:range];
        NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];

        [paragraphStyle setLineSpacing:4];//调整行间距

        [attributedString addAttribute:NSParagraphStyleAttributeName value:paragraphStyle range:NSMakeRange(0, [string length])];

        hotLabel.attributedText = attributedString;