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nlohmann::basic_json::operator!=

bool operator!=(const_reference lhs, const_reference rhs) noexcept;

template<typename ScalarType>
bool operator!=(const_reference lhs, const ScalarType rhs) noexcept;

template<typename ScalarType>
bool operator!=(ScalarType lhs, const const_reference rhs) noexcept;

Compares two JSON values for inequality by calculating !(lhs == rhs).

Template parameters

ScalarType
a scalar type according to std::is_scalar<ScalarType>::value

Parameters

lhs (in)
first value to consider
rhs (in)
second value to consider

Return value

whether the values lhs and rhs are not equal

Exception safety

No-throw guarantee: this function never throws exceptions.

Complexity

Linear.

Examples

Example

The example demonstrates comparing several JSON types.

#include <iostream>
#include <nlohmann/json.hpp>

using json = nlohmann::json;

int main()
{
    // create several JSON values
    json array_1 = {1, 2, 3};
    json array_2 = {1, 2, 4};
    json object_1 = {{"A", "a"}, {"B", "b"}};
    json object_2 = {{"B", "b"}, {"A", "a"}};
    json number_1 = 17;
    json number_2 = 17.000000000000001L;
    json string_1 = "foo";
    json string_2 = "bar";

    // output values and comparisons
    std::cout << std::boolalpha;
    std::cout << array_1 << " != " << array_2 << " " << (array_1 != array_2) << '\n';
    std::cout << object_1 << " != " << object_2 << " " << (object_1 != object_2) << '\n';
    std::cout << number_1 << " != " << number_2 << " " << (number_1 != number_2) << '\n';
    std::cout << string_1 << " != " << string_2 << " " << (string_1 != string_2) << '\n';
}

Output:

[1,2,3] != [1,2,4] true
{"A":"a","B":"b"} != {"A":"a","B":"b"} false
17 != 17.0 false
"foo" != "bar" true
Example

The example demonstrates comparing several JSON types against the null pointer (JSON null).

#include <iostream>
#include <nlohmann/json.hpp>

using json = nlohmann::json;

int main()
{
    // create several JSON values
    json array = {1, 2, 3};
    json object = {{"A", "a"}, {"B", "b"}};
    json number = 17;
    json string = "foo";
    json null;

    // output values and comparisons
    std::cout << std::boolalpha;
    std::cout << array << " != nullptr " << (array != nullptr) << '\n';
    std::cout << object << " != nullptr " << (object != nullptr) << '\n';
    std::cout << number << " != nullptr " << (number != nullptr) << '\n';
    std::cout << string << " != nullptr " << (string != nullptr) << '\n';
    std::cout << null << " != nullptr " << (null != nullptr) << '\n';
}

Output:

[1,2,3] != nullptr true
{"A":"a","B":"b"} != nullptr true
17 != nullptr true
"foo" != nullptr true
null != nullptr false

Version history

  • Added in version 1.0.0.
Last update: May 1, 2022
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