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◆ type_name()
template<template< typename U, typename V, typename... Args > class ObjectType = std::map, template< typename U, typename... Args > class ArrayType = std::vector, class StringType = std::string, class BooleanType = bool, class NumberIntegerType = std::int64_t, class NumberUnsignedType = std::uint64_t, class NumberFloatType = double, template< typename U > class AllocatorType = std::allocator, template< typename T, typename SFINAE=void > class JSONSerializer = adl_serializer>
Returns the type name as string to be used in error messages - usually to indicate that a function was called on a wrong JSON type.
- Returns
- a string representation of a the m_type member:
Value type | return value |
null | "null" |
boolean | "boolean" |
string | "string" |
number | "number" (for all number types) |
object | "object" |
array | "array" |
discarded | "discarded" |
- Exception safety^^ No-throw guarantee: this function never throws exceptions.
- Complexity^^ Constant.
- Example^^ The following code exemplifies type_name() for all JSON
- types. ^^
2 #include <nlohmann/json.hpp> 10 json j_boolean = true; 11 json j_number_integer = -17; 12 json j_number_unsigned = 42u; 13 json j_number_float = 23.42; 14 json j_object = {{ "one", 1}, { "two", 2}}; 15 json j_array = {1, 2, 4, 8, 16}; 16 json j_string = "Hello, world"; 19 std::cout << j_null << " is a " << j_null.type_name() << '\n'; 20 std::cout << j_boolean << " is a " << j_boolean.type_name() << '\n'; 21 std::cout << j_number_integer << " is a " << j_number_integer.type_name() << '\n'; 22 std::cout << j_number_unsigned << " is a " << j_number_unsigned.type_name() << '\n'; 23 std::cout << j_number_float << " is a " << j_number_float.type_name() << '\n'; 24 std::cout << j_object << " is an " << j_object.type_name() << '\n'; 25 std::cout << j_array << " is an " << j_array.type_name() << '\n'; 26 std::cout << j_string << " is a " << j_string.type_name() << '\n'; basic_json<> json default JSON class
Output (play with this example online):^^ null is a null
true is a boolean
-17 is a number
42 is a number
23.42 is a number
{"one":1,"two":2} is an object
[1,2,4,8,16] is an array
"Hello, world" is a string
^^ The example code above can be translated withg++ -std=c++11 -Isingle_include doc/examples/type_name.cpp -o type_name
- See also
- type() – return the type of the JSON value
-
operator value_t() – return the type of the JSON value (implicit)
- Since
- version 1.0.0, public since 2.1.0,
const char* and noexcept since 3.0.0
Definition at line 18691 of file json.hpp.
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