deploy: 7c9208bfb3

2026-07-09 12:05:10 +00:00 · 2026-07-08 18:19:46 +00:00
parent 9a231845c2
commit 279d757031
758 changed files with 56489 additions and 503 deletions
@@ -0,0 +1,98 @@
+# nlohmann::basic_json::operator value_t
+
+```
+constexpr operator value_t() const noexcept;
+```
+
+Return the type of the JSON value as a value from the [`value_t`](https://json.nlohmann.me/api/basic_json/value_t/index.md) enumeration.
+
+## Return value
+
+the type of the JSON value
+
+| Value type                | return value               |
+| ------------------------- | -------------------------- |
+| `null`                    | `value_t::null`            |
+| boolean                   | `value_t::boolean`         |
+| string                    | `value_t::string`          |
+| number (integer)          | `value_t::number_integer`  |
+| number (unsigned integer) | `value_t::number_unsigned` |
+| number (floating-point)   | `value_t::number_float`    |
+| object                    | `value_t::object`          |
+| array                     | `value_t::array`           |
+| binary                    | `value_t::binary`          |
+| discarded                 | `value_t::discarded`       |
+
+## Exception safety
+
+No-throw guarantee: this member function never throws exceptions.
+
+## Complexity
+
+Constant.
+
+## Examples
+
+Example
+
+The following code exemplifies `operator value_t()` for all JSON types.
+
+```
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // create JSON values
+    json j_null;
+    json j_boolean = true;
+    json j_number_integer = -17;
+    json j_number_unsigned = 42u;
+    json j_number_float = 23.42;
+    json j_object = {{"one", 1}, {"two", 2}};
+    json j_array = {1, 2, 4, 8, 16};
+    json j_string = "Hello, world";
+
+    // call operator value_t()
+    json::value_t t_null = j_null;
+    json::value_t t_boolean = j_boolean;
+    json::value_t t_number_integer = j_number_integer;
+    json::value_t t_number_unsigned = j_number_unsigned;
+    json::value_t t_number_float = j_number_float;
+    json::value_t t_object = j_object;
+    json::value_t t_array = j_array;
+    json::value_t t_string = j_string;
+
+    // print types
+    std::cout << std::boolalpha;
+    std::cout << (t_null == json::value_t::null) << '\n';
+    std::cout << (t_boolean == json::value_t::boolean) << '\n';
+    std::cout << (t_number_integer == json::value_t::number_integer) << '\n';
+    std::cout << (t_number_unsigned == json::value_t::number_unsigned) << '\n';
+    std::cout << (t_number_float == json::value_t::number_float) << '\n';
+    std::cout << (t_object == json::value_t::object) << '\n';
+    std::cout << (t_array == json::value_t::array) << '\n';
+    std::cout << (t_string == json::value_t::string) << '\n';
+}
+```
+
+Output:
+
+```
+true
+true
+true
+true
+true
+true
+true
+true
+```
+
+## Version history
+
+- Added in version 1.0.0.
+- Added unsigned integer type in version 2.0.0.
+- Added binary type in version 3.8.0.