JSON for Modern C++  3.6.1

◆ erase() [1/4]

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>
template<class IteratorType , typename std::enable_if< std::is_same< IteratorType, typename basic_json_t::iterator >::value or std::is_same< IteratorType, typename basic_json_t::const_iterator >::value, int >::type = 0>
IteratorType nlohmann::basic_json::erase ( IteratorType  pos)
inline

Removes the element 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.

Parameters
[in]positerator to the element to remove
Returns
Iterator following the last removed element. If the iterator pos refers to the last element, the end() iterator is returned.
Template Parameters
IteratorTypean iterator or const_iterator
Postcondition
Invalidates iterators and references at or after the point of the erase, including the end() iterator.
Exceptions
type_error.307if called on a null value; example: "cannot use erase() with null"
invalid_iterator.202if called on an iterator which does not belong to the current JSON value; example: "iterator does not fit current value"
invalid_iterator.205if called on a primitive type with invalid iterator (i.e., any iterator which is not begin()); example: "iterator out of range"
Complexity
The complexity depends on the type:
  • objects: amortized constant
  • arrays: linear in distance between pos and the end of the container
  • strings: linear in the length of the string
  • other types: constant
Example
The example shows the result of erase() for different JSON types.
1 #include <iostream>
2 #include <nlohmann/json.hpp>
3 
4 using json = nlohmann::json;
5 
6 int main()
7 {
8  // create JSON values
9  json j_boolean = true;
10  json j_number_integer = 17;
11  json j_number_float = 23.42;
12  json j_object = {{"one", 1}, {"two", 2}};
13  json j_array = {1, 2, 4, 8, 16};
14  json j_string = "Hello, world";
15 
16  // call erase
17  j_boolean.erase(j_boolean.begin());
18  j_number_integer.erase(j_number_integer.begin());
19  j_number_float.erase(j_number_float.begin());
20  j_object.erase(j_object.find("two"));
21  j_array.erase(j_array.begin() + 2);
22  j_string.erase(j_string.begin());
23 
24  // print values
25  std::cout << j_boolean << '\n';
26  std::cout << j_number_integer << '\n';
27  std::cout << j_number_float << '\n';
28  std::cout << j_object << '\n';
29  std::cout << j_array << '\n';
30  std::cout << j_string << '\n';
31 }
basic_json<> json
default JSON class
Definition: json.hpp:871

Output (play with this example online):
null
null
null
{"one":1}
[1,2,8,16]
null
The example code above can be translated with
g++ -std=c++11 -Isingle_include doc/examples/erase__IteratorType.cpp -o erase__IteratorType 
See also
erase(IteratorType, IteratorType) – removes the elements in the given range
erase(const typename object_t::key_type&) – removes the element from an object at the given key
erase(const size_type) – removes the element from an array at the given index
Since
version 1.0.0

Definition at line 16404 of file json.hpp.