// (1) iterator erase(iterator pos); const_iterator erase(const_iterator pos); // (2) iterator erase(iterator first, iterator last); const_iterator erase(const_iterator first, const_iterator last); // (3) size_type erase(const typename object_t::key_type& key); // (4) template<typename KeyType> size_type erase(KeyType&& key); // (5) void erase(const size_type idx);
Removes an element from a JSON value specified by iterator pos. The iterator pos must be valid and dereferenceable. Thus, the end() iterator (which is valid, but is not dereferenceable) cannot be used as a value for pos.
If called on a primitive type other than null, the resulting JSON value will be null.
Remove an element range specified by [first; last) from a JSON value. The iterator first does not need to be dereferenceable if first == last: erasing an empty range is a no-op.
If called on a primitive type other than null, the resulting JSON value will be null.
Removes an element from a JSON object by key.
See 3. This overload is only available if KeyType is comparable with typename object_t::key_type and typename object_comparator_t::is_transparent denotes a type.
Removes an element from a JSON array by index.
KeyType : A type for an object key other than json_pointer that is comparable with string_t using object_comparator_t. This can also be a string view (C++17).
pos (in) : iterator to the element to remove
first (in) : iterator to the beginning of the range to remove
last (in) : iterator past the end of the range to remove
key (in) : object key of the elements to remove
idx (in) : array index of the element to remove
pos refers to the last element, the end() iterator is returned.last refers to the last element, the end() iterator is returned.ObjectType is the default std::map type, the return value will always be 0 (key was not found) or 1 (key was found).Strong exception safety: if an exception occurs, the original value stays intact.
type_error.307 if called on a null value; example: "cannot use erase() with null"invalid_iterator.202 if called on an iterator which does not belong to the current JSON value; example: "iterator does not fit current value"invalid_iterator.205 if called on a primitive type with invalid iterator (i.e., any iterator which is not begin()); example: "iterator out of range"type_error.307 if called on a null value; example: "cannot use erase() with null"invalid_iterator.203 if called on iterators which does not belong to the current JSON value; example: "iterators do not fit current value"invalid_iterator.204 if called on a primitive type with invalid iterators (i.e., if first != begin() and last != end()); example: "iterators out of range"type_error.307 when called on a type other than JSON object; example: "cannot use erase() with null"type_error.307 when called on a type other than JSON array; example: "cannot use erase() with null"out_of_range.401 when idx >= size(); example: "array index 17 is out of range"pos and the end of the containerlog(size()) + std::distance(first, last)first and last, plus linear in the distance between last and end of the containerlog(size()) + count(key)log(size()) + count(key)idx and the end of the container.erase, including the end() iterator.Example: (1) remove element given an iterator
The example shows the effect of erase() for different JSON types using an iterator.
#include <iostream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
int main()
{
// create JSON values
json j_boolean = true;
json j_number_integer = 17;
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 erase()
j_boolean.erase(j_boolean.begin());
j_number_integer.erase(j_number_integer.begin());
j_number_float.erase(j_number_float.begin());
j_object.erase(j_object.find("two"));
j_array.erase(j_array.begin() + 2);
j_string.erase(j_string.begin());
// print values
std::cout << j_boolean << '\n';
std::cout << j_number_integer << '\n';
std::cout << j_number_float << '\n';
std::cout << j_object << '\n';
std::cout << j_array << '\n';
std::cout << j_string << '\n';
}
Output:
null
null
null
{"one":1}
[1,2,8,16]
null
Example: (2) remove elements given an iterator range
The example shows the effect of erase() for different JSON types using an iterator range.
#include <iostream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
int main()
{
// create JSON values
json j_boolean = true;
json j_number_integer = 17;
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 erase()
j_boolean.erase(j_boolean.begin(), j_boolean.end());
j_number_integer.erase(j_number_integer.begin(), j_number_integer.end());
j_number_float.erase(j_number_float.begin(), j_number_float.end());
j_object.erase(j_object.find("two"), j_object.end());
j_array.erase(j_array.begin() + 1, j_array.begin() + 3);
j_string.erase(j_string.begin(), j_string.end());
// print values
std::cout << j_boolean << '\n';
std::cout << j_number_integer << '\n';
std::cout << j_number_float << '\n';
std::cout << j_object << '\n';
std::cout << j_array << '\n';
std::cout << j_string << '\n';
}
Output:
null
null
null
{"one":1}
[1,8,16]
null
Example: (3) remove element from a JSON object given a key
The example shows the effect of erase() for different JSON types using an object key.
#include <iostream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
int main()
{
// create a JSON object
json j_object = {{"one", 1}, {"two", 2}};
// call erase()
auto count_one = j_object.erase("one");
auto count_three = j_object.erase("three");
// print values
std::cout << j_object << '\n';
std::cout << count_one << " " << count_three << '\n';
}
Output:
{"two":2}
1 0
Example: (4) remove element from a JSON object given a key using string_view
The example shows the effect of erase() for different JSON types using an object key.
#include <iostream>
#include <string_view>
#include <nlohmann/json.hpp>
using namespace std::string_view_literals;
using json = nlohmann::json;
int main()
{
// create a JSON object
json j_object = {{"one", 1}, {"two", 2}};
// call erase()
auto count_one = j_object.erase("one"sv);
auto count_three = j_object.erase("three"sv);
// print values
std::cout << j_object << '\n';
std::cout << count_one << " " << count_three << '\n';
}
Output:
{"two":2}
1 0
Example: (5) remove element from a JSON array given an index
The example shows the effect of erase() using an array index.
#include <iostream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
int main()
{
// create a JSON array
json j_array = {0, 1, 2, 3, 4, 5};
// call erase()
j_array.erase(2);
// print values
std::cout << j_array << '\n';
}
Output:
[0,1,3,4,5]