iOS可變參數va_list

需求：

用"/"拼接三個字符串，字符串爲空則不拼接，有下邊兩種實現方式

1、if else的實現方式

+ (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;
}
複製代碼

2、可變參數的方式

//建立NSString的分類
/**
 *  用斜線拼接參數
 *  count爲參數個數,其它參數必須是NSString類型(可爲nil)
 *  eg.須要拼接三個字符串 長、寬、高爲 "長/寬/高"  方法調用方式爲[NSString splicWithSlantParamsCount:3, @"長", @"寬", @"高"];
 */
+ (NSString *)stringSplicWithSlantParamsCount:(int)count,...{
    if(count < 1){
        return @"";
    }
    int index = 0;
    va_list args;
    va_start(args, count);
    //拼接後的字符串
    NSString *paramSum = @"";
    NSString *otherParam;
    //循環到結尾就中止循環
    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;
}

複製代碼

+ (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;
}
複製代碼

很明顯，第二中方法擴展性更好，逼格更好

也曾考慮過在封裝的代碼中經過vsnprintf計算可變參數的長度，可是參數有可能爲空，就會致使崩潰，因此最後決定直接傳進來參數的個數