所以我一直在用C语言编写一个程序，可以访问各种加密货币网站的API，比如www.cryptsy.com，我找到了cURL部分并让程序将JSON数据吐出到char *中看起来像这样的变量：
{"success":"1","return":{"balances_available":{"ALF":"0.00000000","AMC":"0.00000000","ADT":"0.00000000","ANC":"0.00000000","ARG":"0.00000000","ASC":"0.00000000","BQC":"0.00000000","BTB":"0.00000000","BTC":"0.00535673","BTG":"0.00000000","CAP":"0.00000000","BTE":"0.00000000","CSC":"0.00000000","CNC":"0.00000000","COL":"0.00000000","CPR":"0.00000000","CLR":"0.00000000","CMC":"0.00000000","CRC":"0.00000000","BUK":"0.00000000","CGB":"0.00000000","Points":"0.00911000","DVC":"0.00000000","DMD":"0.00000000","DGC":"0.00000000","DBL":"0.00000000","ELC":"0.00000000","ELP":"0.00000000","EMD":"0.00000000","EZC":"0.00000000","FST":"0.00000000","FTC":"0.00000000","FLO":"0.00000000","FRK":"0.00000000","FRC":"0.00000000","GLX":"0.00000000","GME":"0.00000000","GLC":"0.00000000","GLD":"0.00000000","GDC":"0.00000000","HBN":"0.00000000","HYC":"0.00000000","IFC":"0.00000000","IXC":"0.00000000","XJO":"0.00000000","JKC":"0.00000000","KGC":"0.00000000","LTC":"0.00000000","LK7":"0.00000000","LKY":"0.00000000","MST":"0.00000000","MEC":"0.00000000","MEM":"0.00000000","MNC":"0.00000000","NMC":"0.00000000","NAN":"0.00000000","NEC":"0.00000000","NET":"0.00000000","NBL":"0.00000000","NRB":"0.00000000","NVC":"0.00000000","ORB":"0.00000000","PYC":"0.00000000","PPC":"0.00000000","CENT":"0.00000000","PHS":"0.00000000","PXC":"0.00000000","XPM":"0.00000000","PTS":"0.00000000","QRK":"0.00000000","RED":"0.00000000","RYC":"0.00000000","SRC":"0.00000000","SXC":"0.00000000","SPT":"0.00000000","SBC":"0.00000000","STR":"0.00000000","TAG":"0.00000000","TEK":"0.00000000","TRC":"0.00000000","TIX":"0.00000000","WDC":"0.00000000","XNC":"0.00000000","YAC":"0.00000000","ZET":"0.00000000"},"balances_hold":{"ALF":"0.00000000","AMC":"0.00000000","ADT":"0.00000000","ANC":"0.00000000","ARG":"0.00000000","ASC":"0.00000000","BQC":"0.00000000","BTB":"0.00000000","BTC":"0.00000000","BTG":"0.00000000","CAP":"0.00000000","BTE":"0.00000000","CSC":"0.00000000","CNC":"0.00000000","COL":"0.00000000","CPR":"0.00000000","CLR":"0.00000000","CMC":"0.00000000","CRC":"0.00000000","BUK":"0.00000000","CGB":"0.00000000","Points":"0.00000000","DVC":"0.00000000","DMD":"0.00000000","DGC":"0.00000000","DBL":"0.00000000","ELC":"0.00000000","ELP":"0.00000000","EMD":"0.00000000","EZC":"0.00000000","FST":"0.00000000","FTC":"0.00000000","FLO":"0.00000000","FRK":"0.00000000","FRC":"0.00000000","GLX":"0.00000000","GME":"0.00000000","GLC":"0.00000000","GLD":"0.00000000","GDC":"0.00000000","HBN":"0.00000000","HYC":"0.00000000","IFC":"0.00000000","IXC":"0.00000000","XJO":"0.00000000","JKC":"0.00000000","KGC":"0.00000000","LTC":"1.10231195","LK7":"0.00000000","LKY":"10.36912507","MST":"0.00000000","MEC":"0.00000000","MEM":"0.00000000","MNC":"0.00000000","NMC":"0.00000000","NAN":"0.00000000","NEC":"0.00000000","NET":"0.00000000","NBL":"0.00000000","NRB":"0.00000000","NVC":"0.00000000","ORB":"0.00000000","PYC":"0.00000000","PPC":"0.00000000","CENT":"0.00000000","PHS":"0.00000000","PXC":"0.00000000","XPM":"0.00000000","PTS":"0.00000000","QRK":"0.00000000","RED":"0.00000000","RYC":"0.00000000","SRC":"0.00000000","SXC":"0.00000000","SPT":"0.00000000","SBC":"0.00000000","STR":"0.00000000","TAG":"0.00000000","TEK":"0.00000000","TRC":"0.83964122","TIX":"0.00000000","WDC":"0.00000000","XNC":"0.00000000","YAC":"0.00000000","ZET":"0.00000000"},"servertimestamp":1387347714,"servertimezone":"EST","serverdatetime":"2013-12-18 01:21:54","openordercount":3}}
对我来说看起来像是有效的JSON数据所以我决定尝试使用jansson进行JSON解析/解码，在我的代码中看起来像这样：
char *data;
if ( argc < 2 )
{
fprintf( stderr, "Must provide URL to fetch.\n" );
return 1;
}
//data = mmpool_api( argv[1] );
data = cryptsy_api( argv[1] );
json_t *root;
json_error_t error;
root = json_loads( data, 0, &error );
if ( !root )
{
fprintf( stderr, "error: on line %d: %s\n", error.line, error.text );
return 1;
}
if ( !json_is_array(root) )
{
fprintf( stderr, "error: root is not an array\n" );
json_decref(root);
return 1;
}
for( int i = 0; i < json_array_size(root); i++ )
{
json_t *data, *success, *returned, *bal_avail;
const char *balance;
data = json_array_get( root, i );
if ( !json_is_object(data) )
{
fprintf( stderr, "error: data %d is not an object\n", i + 1 );
json_decref(root);
return 1;
}
success = json_object_get( data, "success" );
if ( !json_is_number(success))
{
fprintf( stderr, "error: %d: success is not a number", i+1 );
json_decref(root);
return 1;
}
returned = json_object_get(data, "return" );
if ( !json_is_object(returned) )
{
fprintf( stderr, "error: %d: return is not an object", i+1 );
json_decref(root);
return 1;
}
bal_avail = json_object_get( returned, "balances_available" );
if ( !json_is_array( bal_avail ))
{
fprintf( stderr, "error: %d: bal_avail is not an array", i+1 );
json_decref(root);
}
balance = json_string_value(bal_avail);
printf( "%s %.*s\n",
json_string_value(bal_avail),
newline_offset(balance),
balance);
}
json_decref(root);
但是程序只是失败说明root不是一个数组，所以它在JSON代码启动后在第二个if语句中死掉。我注意到jansson有自己的“请求（url）”函数，您可以使用该函数向服务器请求JSON数据，但是为了获取我需要的数据，您需要发送密钥/ API密钥和哈希他们使用SHA512获得有效响应，此功能似乎没有这个功能。
我知道C还有其他用于解码JSON数据的库，但我只是想在切换到JSON-C或其他库之前确保我没有做错。谢谢
EDIT ::
好吧所以我试图改变代码只是解析'root'对象，但它似乎只通过“返回”和“成功”键..也许我仍然不完全理解，但这里是我正在使用的代码试图解析所有内容，我阅读了jansson API指南，如果你想要遍历对象中的每一个key：value对，它会说使用迭代器：
char *data;
if ( argc < 2 )
{
fprintf( stderr, "Must provide URL to fetch.\n" );
return 1;
}
//data = mmpool_api( argv[1] );
data = cryptsy_api( argv[1] );
json_t *root;
json_error_t error;
root = json_loads( data, 0, &error );
if ( !root )
{
fprintf( stderr, "error: on line %d: %s\n", error.line, error.text );
return 1;
}
const char *key;
json_t *value;
void *iter = json_object_iter( root );
while( iter )
{
key = json_object_iter_key(iter);
value = json_object_iter_value(iter);
printf("Key: %s, Value: %f\n", key, json_real_value(value) );
iter = json_object_iter_next(root, iter);
}
json_decref(root);
但它是这样的（只有前两个项是地址，它们是相反的顺序）：
键：返回，值：0.000000 关键：成功，价值：0.000000
答案 0 :(得分：6)
JSON字符串的根元素是一个对象，而不是一个数组。 JSON中的数组用方括号[和]表示，对象用大括号{和}表示。如果您已经知道要访问哪些键，则无需迭代“object”根元素，只需使用json_object_get(root, "keyname");，直到您访问了所需的所有值。