nlohmann::basic_json::is_primitive¶

constexprboolis_primitive()constnoexcept;

This function returns true if and only if the JSON type is primitive (string, number, boolean, null, binary).

Return value¶

true if type is primitive (string, number, boolean, null, or binary), false otherwise.

Exception safety¶

No-throw guarantee: this member function never throws exceptions.

Complexity¶

Constant.

Possible implementation¶

constexprboolis_primitive()constnoexcept
{
returnis_null()||is_string()||is_boolean()||is_number()||is_binary();
}

Notes¶

The term primitive stems from RFC 8259:

JSON can represent four primitive types (strings, numbers, booleans, and null) and two structured types (objects and arrays).

This library extends primitive types to binary types, because binary types are roughly comparable to strings. Hence, is_primitive() returns true for binary values.

Examples¶

#include<iostream>
#include<nlohmann/json.hpp>
usingjson=nlohmann::json;
intmain()
{
// create JSON values
jsonj_null;
jsonj_boolean=true;
jsonj_number_integer=17;
jsonj_number_float=23.42;
jsonj_number_unsigned_integer=12345678987654321u;
jsonj_object={{"one",1},{"two",2}};
jsonj_array={1,2,4,8,16};
jsonj_string="Hello, world";
jsonj_binary=json::binary({1,2,3});
// call is_primitive()
std::cout<<std::boolalpha;
std::cout<<j_null.is_primitive()<<'\n';
std::cout<<j_boolean.is_primitive()<<'\n';
std::cout<<j_number_integer.is_primitive()<<'\n';
std::cout<<j_number_unsigned_integer.is_primitive()<<'\n';
std::cout<<j_number_float.is_primitive()<<'\n';
std::cout<<j_object.is_primitive()<<'\n';
std::cout<<j_array.is_primitive()<<'\n';
std::cout<<j_string.is_primitive()<<'\n';
std::cout<<j_binary.is_primitive()<<'\n';
}

true
true
true
true
true
false
false
true
true

See also¶

• is_structured() returns whether the JSON value is structured
• is_null() returns whether the JSON value is null
• is_string() returns whether the JSON value is a string
• is_boolean() returns whether the JSON value is a boolean
• is_number() returns whether the JSON value is a number
• is_binary() returns whether the JSON value is a binary array

Version history¶

• Added in version 1.0.0.
• Extended to return true for binary types in version 3.8.0.