iOS可变参数va_list

需求：

用"/"拼接三个字符串，字符串为空则不拼接，有下边两种实现方式

一、if else的实现方式

+ (NSString *)getGoodsRuleWithCarLength:(NSString *)carLength andCarType:(NSString *)carType andSpecialRequire:(NSString *)specialRequire andEntrance:(TYTGoodsRuleEntrance)entrance{
    NSString *goodsRule = nil;
    if(carLength.length > 0){
        if(carType.length > 0){
            if(specialRequire.length > 0){
                goodsRule = [NSString stringWithFormat:@"%@/%@/%@",carLength,carType,specialRequire];
            }else{
                goodsRule = [NSString stringWithFormat:@"%@/%@",carLength,carType];
            }
        }else{
            if(specialRequire.length > 0){
                goodsRule = [NSString stringWithFormat:@"%@/%@",carLength,specialRequire];
            }else{
                goodsRule = [NSString stringWithFormat:@"%@",carLength];
            }
        }
    }else{
        if(carType.length > 0){
            if(specialRequire.length > 0){
                goodsRule = [NSString stringWithFormat:@"%@/%@",carType,specialRequire];
            }else{
                goodsRule = [NSString stringWithFormat:@"%@",carType];
            }
        }else{
            if(specialRequire.length > 0){
                goodsRule = [NSString stringWithFormat:@"%@",specialRequire];
            }else{
                goodsRule = @"";
            }
        }
    }
    return goodsRule;
}

二、可变参数的方式

//创建NSString的分类
/**
 *  用斜线拼接参数
 *  count为参数个数,其它参数必须是NSString类型(可为nil)
 *  eg.需要拼接三个字符串 长、宽、高为 "长/宽/高"  方法调用方式为[NSString splicWithSlantParamsCount:3, @"长", @"宽", @"高"];
 */
+ (NSString *)stringSplicWithSlantParamsCount:(int)count,...{
    if(count < 1){
        return @"";
    }
    int index = 0;
    va_list args;
    va_start(args, count);
    //拼接后的字符串
    NSString *paramSum = @"";
    NSString *otherParam;
    //循环到结尾就停止循环
    while(index<count){
        index ++;
        otherParam = va_arg(args, NSString *);
        if(paramSum.length > 0){
            if(otherParam.length > 0){
                paramSum = [NSString stringWithFormat:@"%@/%@",paramSum,otherParam];
            }
        }else{
            if(otherParam.length > 0){
                paramSum = otherParam;
            }
        }
    }
    va_end(args);
    return paramSum;
}

+ (NSString *)getGoodsRuleWithCarLength:(NSString *)carLength andCarType:(NSString *)carType andSpecialRequire:(NSString *)specialRequire andEntrance:(TYTGoodsRuleEntrance)entrance{
    //用"/"拼接字符串
    NSString *goodsRule = [NSString stringSplicWithSlantParamsCount:3, carLength, carType, specialRequire];
    return goodsRule;
}

很明显，第二中方法扩展性更好，逼格更好

也曾考虑过在封装的代码中通过vsnprintf计算可变参数的长度，但是参数有可能为空，就会导致崩溃，所以最后决定直接传进来参数的个数

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