c - 如何使用 json-c 库遍历 C 中的键和值？

Question

我正在使用 json-c 来解析 json。是否可以遍历键和值。json_object_object_get_ex() ：这个函数需要事先知道键是什么。如果我们不知道密钥，我们必须遍历它们怎么办。

Answer 1

您可以从json_object_object_foreach宏开始

#define json_object_object_foreach(obj, key, val)
char * key;
struct json_object * val;
for (struct lh_entry * entry = json_object_get_object(obj) -> head;
  ({
    if (entry) {
      key = (char * ) entry -> k;
      val = (struct json_object * ) entry -> v;
    };entry;
  }); entry = entry -> next)

对于用法，这篇文章有一个很好的例子。

#include <json/json.h>

#include <stdio.h>

int main() {
  char * string = "{"
  sitename " : "
  joys of programming ",
  "tags": ["c", "c++", "java", "PHP"],
  "author-details": {
    "name": "Joys of Programming",
    "Number of Posts": 10
  }
}
";
json_object * jobj = json_tokener_parse(string);
enum json_type type;
json_object_object_foreach(jobj, key, val) {
  printf("type: ", type);
  type = json_object_get_type(val);
  switch (type) {
  case json_type_null:
    printf("json_type_nulln");
    break;
  case json_type_boolean:
    printf("json_type_booleann");
    break;
  case json_type_double:
    printf("json_type_doublen");
    break;
  case json_type_int:
    printf("json_type_intn");
    break;
  case json_type_object:
    printf("json_type_objectn");
    break;
  case json_type_array:
    printf("json_type_arrayn");
    break;
  case json_type_string:
    printf("json_type_stringn");
    break;
  }
}
}