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首先給大家?guī)?lái)網(wǎng)上常見(jiàn)的Json字符串轉(zhuǎn)字典，字典轉(zhuǎn)Json字符串代碼

Json字符串轉(zhuǎn)字典

+ (NSDictionary *)dictionaryWithJsonString:(NSString *)jsonString
{
    if (jsonString == nil) {
        return nil;
    }

    NSData *jsonData = [jsonString dataUsingEncoding:NSUTF8StringEncoding];
    NSError *err;
    NSDictionary *dic = [NSJSONSerialization JSONObjectWithData:jsonData
                                                        options:NSJSONReadingMutableContainers
                                                          error:&err];
    if(err)
    {
        NSLog(@"json解析失敳吵睢：%@",err);
        return nil;
    }
    return dic;
}

字典轉(zhuǎn)Json字符串

+ (NSString *)jsonStringWithDict:(NSDictionary *)dict {
    NSError *error;
    NSData *jsonData = [NSJSONSerialization dataWithJSONObject:dict options:NSJSONWritingPrettyPrinted error:&error];
    NSString *jsonString;
    if (!jsonData) {
        NSLog(@"%@",error);
    }else{
        jsonString = [[NSString alloc]initWithData:jsonData encoding:NSUTF8StringEncoding];
    }
    return jsonString;
}

有時(shí)候我們需要的把字典轉(zhuǎn)成Json字符串（去掉空格檐什、換行符等）瞳收、我們一般的做法

+ (NSString *)jsonStringWithDict:(NSDictionary *)dict {
    NSError *error;
    NSData *jsonData = [NSJSONSerialization dataWithJSONObject:dict options:NSJSONWritingPrettyPrinted error:&error];
    
    NSString *jsonString;
    if (!jsonData) {
        NSLog(@"%@",error);
    }else{
        jsonString = [[NSString alloc]initWithData:jsonData encoding:NSUTF8StringEncoding];
    }
    
    NSMutableString *mutStr = [NSMutableString stringWithString:jsonString];
    NSRange range = {0,jsonString.length};
    //去掉字符串中的空格
    [mutStr replaceOccurrencesOfString:@" " withString:@"" options:NSLiteralSearch range:range];
    NSRange range2 = {0,mutStr.length};
    //去掉字符串中的換行符
    [mutStr replaceOccurrencesOfString:@"\n" withString:@"" options:NSLiteralSearch range:range2];
    return mutStr;
}

這種做法看似解決了、Json字符串里面的空格厢汹、換行符，實(shí)際上把鍵值對(duì)里面的key,value的空格也去掉

其實(shí)iOS11已經(jīng)存在對(duì)應(yīng)的枚舉類(lèi)型谐宙，把字典轉(zhuǎn)換成單行Json字符串的data

下面我們就介紹次枚舉

NSJSONWritingOptions

typedef NS_OPTIONS(NSUInteger, NSJSONWritingOptions) {
    NSJSONWritingPrettyPrinted = (1UL << 0),

    /* Sorts dictionary keys for output using [NSLocale systemLocale]. Keys are compared using NSNumericSearch. The specific sorting method used is subject to change.
     */
    NSJSONWritingSortedKeys API_AVAILABLE(macos(10.13), ios(11.0), watchos(4.0), tvos(11.0)) = (1UL << 1)
} API_AVAILABLE(macos(10.7), ios(5.0), watchos(2.0), tvos(9.0));

對(duì)上面字段的解釋：
NSJSONWritingPrettyPrinted = (1UL << 0) //是將生成的json數(shù)據(jù)格式化輸出烫葬，這樣可讀性高
NSJSONWritingSortedKeys //輸出的json字符串就是一整行

注意 不設(shè)置則輸出的json字符串就是一整行。

最后我們改上面字典轉(zhuǎn)Json字符串的代碼為下面代碼：

+ (NSString *)jsonStringWithDict:(NSDictionary *)dict {
    NSError *error;
    
    // 注
    //NSData *jsonData = [NSJSONSerialization dataWithJSONObject:dict options:NSJSONWritingSortedKeys error:&error];
    
    // NSJSONWritingSortedKeys這個(gè)枚舉類(lèi)型只適用iOS11所以我是使用下面寫(xiě)法解決的
    NSData *jsonData = [NSJSONSerialization dataWithJSONObject:dict options:nil error:&error];

    NSString *jsonString;
    if (!jsonData) {
        NSLog(@"%@",error);
    }else{
        jsonString = [[NSString alloc]initWithData:jsonData encoding:NSUTF8StringEncoding];
    }

    return jsonString;
}

這樣我們得到的Json字符串就是一行沒(méi)有空格和換行符的字符串

如果有更好的方法凡蜻、不吝賜教搭综！