JSON for Modern C++ 3.8.0

accept
accept
accept
allocator_type
array
array_t
at
at
at
at
at
at
back
back
basic_json
basic_json
basic_json
basic_json
basic_json
basic_json
basic_json
basic_json
basic_json
basic_json
begin
begin
binary
binary
binary
binary
binary_t
boolean_t
cbegin
cbor_tag_handler_t
cend
clear
const_iterator
const_pointer
const_reference
const_reverse_iterator
contains
contains
count
crbegin
crend
detail::external_constructor
diff
difference_type
dump
emplace
emplace_back
empty
end
end
erase
erase
erase
erase
error_handler_t
exception
find
find
flatten
from_bson
from_bson
from_bson
from_bson
from_cbor
from_cbor
from_cbor
from_cbor
from_msgpack
from_msgpack
from_msgpack
from_msgpack
from_ubjson
from_ubjson
from_ubjson
from_ubjson
front
front
get
get
get
get
get
get
get_allocator
get_binary
get_binary
get_ptr
get_ptr
get_ref
get_ref
get_to
get_to
get_to
initializer_list_t
input_format_t
insert
insert
insert
insert
insert
insert
insert_iterator
invalid_iterator
is_array
is_binary
is_boolean
is_discarded
is_null
is_number
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is_number_integer
is_number_unsigned
is_object
is_primitive
is_string
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items
iterator
iterator_wrapper
iterator_wrapper
json_pointer
json_sax_t
json_serializer
max_size
merge_patch
meta
number_float_t
number_integer_t
number_unsigned_t
object
object_comparator_t
object_t
operator value_t
operator ValueType
operator!=
operator!=
operator!=
operator+=
operator+=
operator+=
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operator<
operator<
operator<
operator<<
operator<<
operator<=
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operator=
operator==
operator==
operator==
operator>
operator>
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operator>>
operator>>
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operator[]
operator[]
operator[]
operator[]
operator[]
operator[]
operator[]
other_error
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parse
parse
parse
parse_error
parse_event_t
parser_callback_t
patch
pointer
push_back
push_back
push_back
push_back
rbegin
rbegin
reference
rend
rend
reverse_iterator
sax_parse
sax_parse
sax_parse
size
size_type
string_t
swap
swap
swap
swap
swap
swap
swap
to_bson
to_bson
to_bson
to_cbor
to_cbor
to_cbor
to_msgpack
to_msgpack
to_msgpack
to_ubjson
to_ubjson
to_ubjson
type
type_error
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unflatten
update
update
value
value
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value_t
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~basic_json
| ## ◆ contains() [2/2] template<typename KeyT , typename std::enable_if< !std::is_same< typename std::decay< KeyT >::type, json_pointer >::value, int >::type = 0>
bool nlohmann::basic_json::contains | ( | KeyT && | key | ) | const
| inline
  Check whether an element exists in a JSON object with key equivalent to key. If the element is not found or the JSON value is not an object, false is returned. Note This method always returns false when executed on a JSON type that is not an object. Parameters
  [in] | key | key value to check its existence.
  Returns true if an element with specified key exists. If no such element with such key is found or the JSON value is not an object, false is returned. Complexity Logarithmic in the size of the JSON object. Example The following code shows an example for `contains()`. 1 #include <iostream> 2 #include <nlohmann/json.hpp> 3 4 using json = nlohmann::json; 5 6 int main() 7 { 8 // create some JSON values 9 json j_object = R"( {"key": "value"} )"_json; 10 json j_array = R"( [1, 2, 3] )"_json; 11 12 // call contains 13 std::cout << std::boolalpha << 14 "j_object contains 'key': " << j_object.contains("key") << '\n' << 15 "j_object contains 'another': " << j_object.contains("another") << '\n' << 16 "j_array contains 'key': " << j_array.contains("key") << std::endl; 17 } Output (play with this example online):
      j_object contains 'key': true
      j_object contains 'another': false
      j_array contains 'key': false
  The example code above can be translated with
      g++ -std=c++11 -Isingle_include doc/examples/contains.cpp -o contains
See also find(KeyT&&) – returns an iterator to an object element contains(const json_pointer&) const – checks the existence for a JSON pointer Since version 3.6.0 Definition at line 20806 of file json.hpp.

nlohmann::json
basic_json<> json
default JSON class
Definition: json.hpp:2933