mirror of https://github.com/nlohmann/json.git
proposal for emplace/emplace_back (#349)
Niels
parent
9ca00e4880
commit
1be73b903e
|
|
@ -0,0 +1,23 @@
|
|||
#include <json.hpp>
|
||||
|
||||
using json = nlohmann::json;
|
||||
|
||||
int main()
|
||||
{
|
||||
// create JSON values
|
||||
json object = {{"one", 1}, {"two", 2}};
|
||||
json null;
|
||||
|
||||
// print values
|
||||
std::cout << object << '\n';
|
||||
std::cout << null << '\n';
|
||||
|
||||
// add values
|
||||
object.emplace("three", 3);
|
||||
null.emplace("A", "a");
|
||||
null.emplace("B", "b");
|
||||
|
||||
// print values
|
||||
std::cout << object << '\n';
|
||||
std::cout << null << '\n';
|
||||
}
|
||||
|
|
@ -0,0 +1 @@
|
|||
<a target="_blank" href="http://melpon.org/wandbox/permlink/Qg5Ogrh8yFrwT2GY"><b>online</b></a>
|
||||
|
|
@ -0,0 +1,4 @@
|
|||
{"one":1,"two":2}
|
||||
null
|
||||
{"one":1,"three":3,"two":2}
|
||||
{"A":"a","B":"b"}
|
||||
|
|
@ -0,0 +1,23 @@
|
|||
#include <json.hpp>
|
||||
|
||||
using json = nlohmann::json;
|
||||
|
||||
int main()
|
||||
{
|
||||
// create JSON values
|
||||
json array = {1, 2, 3, 4, 5};
|
||||
json null;
|
||||
|
||||
// print values
|
||||
std::cout << array << '\n';
|
||||
std::cout << null << '\n';
|
||||
|
||||
// add values
|
||||
array.emplace_back(6);
|
||||
null.emplace_back("first");
|
||||
null.emplace_back(3, "second");
|
||||
|
||||
// print values
|
||||
std::cout << array << '\n';
|
||||
std::cout << null << '\n';
|
||||
}
|
||||
|
|
@ -0,0 +1 @@
|
|||
<a target="_blank" href="http://melpon.org/wandbox/permlink/jdch45YEMX94DvlH"><b>online</b></a>
|
||||
|
|
@ -0,0 +1,4 @@
|
|||
[1,2,3,4,5]
|
||||
null
|
||||
[1,2,3,4,5,6]
|
||||
["first",["second","second","second"]]
|
||||
11
doc/index.md
11
doc/index.md
|
|
@ -197,7 +197,7 @@ The container functions known from STL have been extended to support the differe
|
|||
<td class="ok_green">@link nlohmann::basic_json::max_size `max_size` @endlink (returns `0`)</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td rowspan="5">modifiers</td>
|
||||
<td rowspan="6">modifiers</td>
|
||||
<td>`clear`</td>
|
||||
<td class="ok_green">@link nlohmann::basic_json::clear `clear` @endlink</td>
|
||||
<td class="ok_green">@link nlohmann::basic_json::clear `clear` @endlink</td>
|
||||
|
|
@ -233,6 +233,15 @@ The container functions known from STL have been extended to support the differe
|
|||
<td class="nok_throws">throws `std::domain_error`</td>
|
||||
<td class="ok_green">@link nlohmann::basic_json::push_back(const typename object_t::value_type & val) `push_back` @endlink (creates object)<br>@link nlohmann::basic_json::push_back(const nlohmann::basic_json &) `push_back` @endlink (creates array)</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>`emplace` / `emplace_back`</td>
|
||||
<td class="ok_green">@link nlohmann::basic_json::emplace() `emplace` @endlink</td>
|
||||
<td class="ok_green">@link nlohmann::basic_json::emplace_back() `emplace_back` @endlink</td>
|
||||
<td class="nok_throws">throws `std::domain_error`</td>
|
||||
<td class="nok_throws">throws `std::domain_error`</td>
|
||||
<td class="nok_throws">throws `std::domain_error`</td>
|
||||
<td class="ok_green">@link nlohmann::basic_json::emplace() `emplace` @endlink (creates object)<br>@link nlohmann::basic_json::emplace_back() `emplace_back` @endlink (creates array)</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>`swap`</td>
|
||||
<td class="ok_green">@link nlohmann::basic_json::swap `swap` @endlink</td>
|
||||
|
|
|
|||
84
src/json.hpp
84
src/json.hpp
|
|
@ -5053,6 +5053,90 @@ class basic_json
|
|||
return *this;
|
||||
}
|
||||
|
||||
/*!
|
||||
@brief add an object to an array
|
||||
|
||||
Creates a JSON value from the passed parameters @a args to the end of the
|
||||
JSON value. If the function is called on a JSON null value, an empty array
|
||||
is created before appending the value created from @a args.
|
||||
|
||||
@param[in] args arguments to forward to a constructor of @ref basic_json
|
||||
@tparam Args compatible types to create a @ref basic_json object
|
||||
|
||||
@throw std::domain_error when called on a type other than JSON array or
|
||||
null; example: `"cannot use emplace_back() with number"`
|
||||
|
||||
@complexity Amortized constant.
|
||||
|
||||
@liveexample{The example shows how `push_back()` can be used to add
|
||||
elements to a JSON array. Note how the `null` value was silently converted
|
||||
to a JSON array.,emplace_back}
|
||||
|
||||
@since version 2.0.8
|
||||
*/
|
||||
template<class... Args>
|
||||
void emplace_back(Args&& ... args)
|
||||
{
|
||||
// emplace_back only works for null objects or arrays
|
||||
if (not(is_null() or is_array()))
|
||||
{
|
||||
throw std::domain_error("cannot use emplace_back() with " + type_name());
|
||||
}
|
||||
|
||||
// transform null object into an array
|
||||
if (is_null())
|
||||
{
|
||||
m_type = value_t::array;
|
||||
m_value = value_t::array;
|
||||
assert_invariant();
|
||||
}
|
||||
|
||||
// add element to array (perfect forwarding)
|
||||
m_value.array->emplace_back(std::forward<Args>(args)...);
|
||||
}
|
||||
|
||||
/*!
|
||||
@brief add an object to an object
|
||||
|
||||
Creates a JSON value from the passed parameters @a args to the JSON
|
||||
object. If the function is called on a JSON null value, an empty object
|
||||
is created before appending the value created from @a args.
|
||||
|
||||
@param[in] args arguments to forward to a constructor of @ref basic_json
|
||||
@tparam Args compatible types to create a @ref basic_json object
|
||||
|
||||
@throw std::domain_error when called on a type other than JSON object or
|
||||
null; example: `"cannot use emplace() with number"`
|
||||
|
||||
@complexity Logarithmic in the size of the container, O(log(`size()`)).
|
||||
|
||||
@liveexample{The example shows how `emplace()` can be used to add elements
|
||||
to a JSON object. Note how the `null` value was silently converted to a
|
||||
JSON object.,emplace}
|
||||
|
||||
@since version 2.0.8
|
||||
*/
|
||||
template<class... Args>
|
||||
void emplace(Args&& ... args)
|
||||
{
|
||||
// emplace only works for null objects or arrays
|
||||
if (not(is_null() or is_object()))
|
||||
{
|
||||
throw std::domain_error("cannot use emplace() with " + type_name());
|
||||
}
|
||||
|
||||
// transform null object into an object
|
||||
if (is_null())
|
||||
{
|
||||
m_type = value_t::object;
|
||||
m_value = value_t::object;
|
||||
assert_invariant();
|
||||
}
|
||||
|
||||
// add element to array (perfect forwarding)
|
||||
m_value.object->emplace(std::forward<Args>(args)...);
|
||||
}
|
||||
|
||||
/*!
|
||||
@brief inserts element
|
||||
|
||||
|
|
|
|||
|
|
@ -5053,6 +5053,90 @@ class basic_json
|
|||
return *this;
|
||||
}
|
||||
|
||||
/*!
|
||||
@brief add an object to an array
|
||||
|
||||
Creates a JSON value from the passed parameters @a args to the end of the
|
||||
JSON value. If the function is called on a JSON null value, an empty array
|
||||
is created before appending the value created from @a args.
|
||||
|
||||
@param[in] args arguments to forward to a constructor of @ref basic_json
|
||||
@tparam Args compatible types to create a @ref basic_json object
|
||||
|
||||
@throw std::domain_error when called on a type other than JSON array or
|
||||
null; example: `"cannot use emplace_back() with number"`
|
||||
|
||||
@complexity Amortized constant.
|
||||
|
||||
@liveexample{The example shows how `push_back()` can be used to add
|
||||
elements to a JSON array. Note how the `null` value was silently converted
|
||||
to a JSON array.,emplace_back}
|
||||
|
||||
@since version 2.0.8
|
||||
*/
|
||||
template<class... Args>
|
||||
void emplace_back(Args&& ... args)
|
||||
{
|
||||
// emplace_back only works for null objects or arrays
|
||||
if (not(is_null() or is_array()))
|
||||
{
|
||||
throw std::domain_error("cannot use emplace_back() with " + type_name());
|
||||
}
|
||||
|
||||
// transform null object into an array
|
||||
if (is_null())
|
||||
{
|
||||
m_type = value_t::array;
|
||||
m_value = value_t::array;
|
||||
assert_invariant();
|
||||
}
|
||||
|
||||
// add element to array (perfect forwarding)
|
||||
m_value.array->emplace_back(std::forward<Args>(args)...);
|
||||
}
|
||||
|
||||
/*!
|
||||
@brief add an object to an object
|
||||
|
||||
Creates a JSON value from the passed parameters @a args to the JSON
|
||||
object. If the function is called on a JSON null value, an empty object
|
||||
is created before appending the value created from @a args.
|
||||
|
||||
@param[in] args arguments to forward to a constructor of @ref basic_json
|
||||
@tparam Args compatible types to create a @ref basic_json object
|
||||
|
||||
@throw std::domain_error when called on a type other than JSON object or
|
||||
null; example: `"cannot use emplace() with number"`
|
||||
|
||||
@complexity Logarithmic in the size of the container, O(log(`size()`)).
|
||||
|
||||
@liveexample{The example shows how `emplace()` can be used to add elements
|
||||
to a JSON object. Note how the `null` value was silently converted to a
|
||||
JSON object.,emplace}
|
||||
|
||||
@since version 2.0.8
|
||||
*/
|
||||
template<class... Args>
|
||||
void emplace(Args&& ... args)
|
||||
{
|
||||
// emplace only works for null objects or arrays
|
||||
if (not(is_null() or is_object()))
|
||||
{
|
||||
throw std::domain_error("cannot use emplace() with " + type_name());
|
||||
}
|
||||
|
||||
// transform null object into an object
|
||||
if (is_null())
|
||||
{
|
||||
m_type = value_t::object;
|
||||
m_value = value_t::object;
|
||||
assert_invariant();
|
||||
}
|
||||
|
||||
// add element to array (perfect forwarding)
|
||||
m_value.object->emplace(std::forward<Args>(args)...);
|
||||
}
|
||||
|
||||
/*!
|
||||
@brief inserts element
|
||||
|
||||
|
|
|
|||
|
|
@ -258,6 +258,74 @@ TEST_CASE("modifiers")
|
|||
}
|
||||
}
|
||||
|
||||
SECTION("emplace_back()")
|
||||
{
|
||||
SECTION("to array")
|
||||
{
|
||||
SECTION("null")
|
||||
{
|
||||
json j;
|
||||
j.emplace_back(1);
|
||||
j.emplace_back(2);
|
||||
CHECK(j.type() == json::value_t::array);
|
||||
CHECK(j == json({1, 2}));
|
||||
}
|
||||
|
||||
SECTION("array")
|
||||
{
|
||||
json j = {1, 2, 3};
|
||||
j.emplace_back("Hello");
|
||||
CHECK(j.type() == json::value_t::array);
|
||||
CHECK(j == json({1, 2, 3, "Hello"}));
|
||||
}
|
||||
|
||||
SECTION("multiple values")
|
||||
{
|
||||
json j;
|
||||
j.emplace_back(3, "foo");
|
||||
CHECK(j.type() == json::value_t::array);
|
||||
CHECK(j == json({{"foo", "foo", "foo"}}));
|
||||
}
|
||||
}
|
||||
|
||||
SECTION("other type")
|
||||
{
|
||||
json j = 1;
|
||||
CHECK_THROWS_AS(j.emplace_back("Hello"), std::domain_error);
|
||||
CHECK_THROWS_WITH(j.emplace_back("Hello"), "cannot use emplace_back() with number");
|
||||
}
|
||||
}
|
||||
|
||||
SECTION("emplace()")
|
||||
{
|
||||
SECTION("to object")
|
||||
{
|
||||
SECTION("null")
|
||||
{
|
||||
json j;
|
||||
j.emplace("foo", "bar");
|
||||
j.emplace("baz", "bam");
|
||||
CHECK(j.type() == json::value_t::object);
|
||||
CHECK(j == json({{"baz", "bam"}, {"foo", "bar"}}));
|
||||
}
|
||||
|
||||
SECTION("object")
|
||||
{
|
||||
json j = {{"foo", "bar"}};
|
||||
j.emplace("baz", "bam");
|
||||
CHECK(j.type() == json::value_t::object);
|
||||
CHECK(j == json({{"baz", "bam"}, {"foo", "bar"}}));
|
||||
}
|
||||
}
|
||||
|
||||
SECTION("other type")
|
||||
{
|
||||
json j = 1;
|
||||
CHECK_THROWS_AS(j.emplace("foo", "bar"), std::domain_error);
|
||||
CHECK_THROWS_WITH(j.emplace("foo", "bar"), "cannot use emplace() with number");
|
||||
}
|
||||
}
|
||||
|
||||
SECTION("operator+=")
|
||||
{
|
||||
SECTION("to array")
|
||||
|
|
|
|||
Loading…
Reference in New Issue