我有YAJL解析我所包含的示例中给出的简单元素没有问题。 (字符串,整数,数组,......)
示例代码可在此处找到:http://lloyd.github.io/yajl/yajl-2.0.1/example_2parse_config_8c-example.html
但现在我有这种类型的JSON对象:
{
"cmd":2,
"properties":
[
{
"idx":40,
"val":8813.602692
},
{
"idx":41,
"val":960
},
{
"idx":42,
"val":2
},
{
"idx":48,
"val":9
}
]
}
我可以检索命令(参见链接示例中使用的变量的定义):
const char * path[] = {"cmd", (const char *) 0 };
yajl_val v = yajl_tree_get(ynode, path, yajl_t_number);
if (v)
*cmd = (commands)((int)YAJL_GET_INTEGER(v));
我可以使用:
获取属性数组的引用int ar_sz;
const char * path[] = {"properties", (const char *) 0 };
yajl_val v = yajl_tree_get(ynode, path, yajl_t_array);
if (v)
{
ar_sz = v->u.array.len;
}
它给了我正确的数组大小,但我不知道如何从数组元素中检索嵌套元素idx和val。
非常感谢任何帮助
答案 0 :(得分:5)
通过yajl_tree.h
具体查看yajl_val_s
结构:
{
const char * path[] = { "properties", (const char *) 0 };
yajl_val v = yajl_tree_get( node, path, yajl_t_array );
if ( v && YAJL_IS_ARRAY( v ) ) {
printf( "is array\n" );
// iterate over array elements,
// it's an array so access array.len inside yajl_val_s.union
size_t len = v->u.array.len;
int i;
for ( i = 0; i < len; ++i ) {
// get ref to one object in array at a time
yajl_val obj = v->u.array.values[ i ]; // object
// iterate over values in object: pairs of (key,value)
// u.object.len tells you number of elements
size_t nelem = obj->u.object.len;
int ii;
for ( ii = 0; ii < nelem; ++ii ) {
// key is just char *
const char * key = obj->u.object.keys[ ii ]; // key
// values is an array object
yajl_val val = obj->u.object.values[ ii ]; // val
// example: check if double,
// could do more checks or switch on value ...
if ( YAJL_IS_DOUBLE( val ) )
printf( "%s/%f ", key, val->u.number.d );
}
printf( "\n" );
}
} else { printf( "is not array\n" ); }
}
输出应该是这样的:
is array
idx/40.000000 val/8813.602692
idx/41.000000 val/960.000000
idx/42.000000 val/2.000000
idx/48.000000 val/9.000000