deploy: 63c10a51fc

api/basic_json/parse_event_t/index.md

@@ -22,6 +22,72 @@ The parser callback distinguishes the following events:
 
 ## Examples
 
+Example
+
+The following code parses a small JSON text with a parser callback that reports every event together with its depth and keeps every value (by always returning `true`).
+
+```
+#include <iostream>
+#include <string>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+// translate a parse_event_t to a human-readable name
+std::string event_name(json::parse_event_t event)
+{
+    switch (event)
+    {
+        case json::parse_event_t::object_start:
+            return "object_start";
+        case json::parse_event_t::object_end:
+            return "object_end";
+        case json::parse_event_t::array_start:
+            return "array_start";
+        case json::parse_event_t::array_end:
+            return "array_end";
+        case json::parse_event_t::key:
+            return "key";
+        case json::parse_event_t::value:
+            return "value";
+        default:
+            return "unknown";
+    }
+}
+
+int main()
+{
+    // a small JSON text
+    auto text = R"({"pi": 3.141, "numbers": [1, 2]})";
+
+    // parse the text and report every event together with its depth;
+    // returning true keeps every value unchanged
+    json j = json::parse(text, [](int depth, json::parse_event_t event, json& /*parsed*/)
+    {
+        std::cout << depth << " " << event_name(event) << '\n';
+        return true;
+    });
+
+    // the callback did not change anything, so the parsed value is unaffected
+    std::cout << j << '\n';
+}
+```
+
+Output:
+
+```
+0 object_start
+1 key
+1 value
+1 key
+1 array_start
+2 value
+2 value
+1 array_end
+0 object_end
+{"numbers":[1,2],"pi":3.141}
+```
+
 ## See also
 
 - [parser_callback_t](https://json.nlohmann.me/api/basic_json/parser_callback_t/index.md) callback function type for the parser