JSON for Modern C++ 3.10.4

◆ is_string()

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, class BinaryType = std::vector<std::uint8_t>>
constexpr bool nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer, BinaryType >::is_string ( ) const
inlineconstexprnoexcept

This function returns true if and only if the JSON value is a string.

Returns
true if type is string, false otherwise.
Complexity
Constant.
Exception safety
No-throw guarantee: this member function never throws exceptions.
Example
The following code exemplifies is_string() for all JSON types.
1#include <iostream>
2#include <nlohmann/json.hpp>
3
4using json = nlohmann::json;
5
6int main()
7{
8 // create JSON values
9 json j_null;
10 json j_boolean = true;
11 json j_number_integer = 17;
12 json j_number_float = 23.42;
13 json j_number_unsigned_integer = 12345678987654321u;
14 json j_object = {{"one", 1}, {"two", 2}};
15 json j_array = {1, 2, 4, 8, 16};
16 json j_string = "Hello, world";
17 json j_binary = json::binary({1, 2, 3});
18
19 // call is_string()
20 std::cout << std::boolalpha;
21 std::cout << j_null.is_string() << '\n';
22 std::cout << j_boolean.is_string() << '\n';
23 std::cout << j_number_integer.is_string() << '\n';
24 std::cout << j_number_unsigned_integer.is_string() << '\n';
25 std::cout << j_number_float.is_string() << '\n';
26 std::cout << j_object.is_string() << '\n';
27 std::cout << j_array.is_string() << '\n';
28 std::cout << j_string.is_string() << '\n';
29 std::cout << j_binary.is_string() << '\n';
30}
basic_json<> json
default JSON class
Definition: json.hpp:3472

Output (play with this example online):
false
false
false
false
false
false
false
true
false
The example code above can be translated with
g++ -std=c++11 -Isingle_include doc/examples/is_string.cpp -o is_string 
Since
version 1.0.0

Definition at line 20255 of file json.hpp.