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Implement contains() member function #1474

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merged 2 commits into from
Feb 13, 2019
Merged

Implement contains() member function #1474

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6a5db00
Implement contains() to check existence of a key
nickaein Feb 10, 2019
e93f305
Add unit-test for contains() member function
nickaein Feb 10, 2019
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33 changes: 33 additions & 0 deletions include/nlohmann/json.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3957,6 +3957,39 @@ class basic_json
return is_object() ? m_value.object->count(std::forward<KeyT>(key)) : 0;
}

/*!
@brief check the existence of an element in a JSON object

Check whether an element exists in a JSON object with key equivalent to
@a 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.

@param[in] key key value to check its existence.

@return true if an element with specified @a 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.

@since version 3.6.0
*/
template<typename KeyT>
bool contains(KeyT&& key) const
{
if (is_object())
{
return (m_value.object->find(std::forward<KeyT>(key)) != m_value.object->end());
}
else
{
return false;
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Should this throw?

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It seems std::map::find cannot be marked as noexcept. I am not sure if we can guarantee that conditions not happening in our case.

}
}

/// @}


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33 changes: 33 additions & 0 deletions single_include/nlohmann/json.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -16456,6 +16456,39 @@ class basic_json
return is_object() ? m_value.object->count(std::forward<KeyT>(key)) : 0;
}

/*!
@brief check the existence of an element in a JSON object

Check whether an element exists in a JSON object with key equivalent to
@a 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.

@param[in] key key value to check its existence.

@return true if an element with specified @a 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.

@since version 3.6.0
*/
template<typename KeyT>
bool contains(KeyT&& key) const
{
if (is_object())
{
return (m_value.object->find(std::forward<KeyT>(key)) != m_value.object->end());
}
else
{
return false;
}
}

/// @}


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87 changes: 87 additions & 0 deletions test/src/unit-element_access2.cpp
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Expand Up @@ -982,6 +982,93 @@ TEST_CASE("element access 2")
}
}
}

SECTION("check existence of key in an object")
{
SECTION("existing element")
{
for (auto key :
{"integer", "unsigned", "floating", "null", "string", "boolean", "object", "array"
})
{
CHECK(j.contains(key) == true);
CHECK(j_const.contains(key) == true);
}
}

SECTION("nonexisting element")
{
CHECK(j.contains("foo") == false);
CHECK(j_const.contains("foo") == false);
}

SECTION("all types")
{
SECTION("null")
{
json j_nonobject(json::value_t::null);
const json j_nonobject_const(j_nonobject);
CHECK(j_nonobject.contains("foo") == false);
CHECK(j_nonobject_const.contains("foo") == false);
}

SECTION("string")
{
json j_nonobject(json::value_t::string);
const json j_nonobject_const(j_nonobject);
CHECK(j_nonobject.contains("foo") == false);
CHECK(j_nonobject_const.contains("foo") == false);
}

SECTION("object")
{
json j_nonobject(json::value_t::object);
const json j_nonobject_const(j_nonobject);
CHECK(j_nonobject.contains("foo") == false);
CHECK(j_nonobject_const.contains("foo") == false);
}

SECTION("array")
{
json j_nonobject(json::value_t::array);
const json j_nonobject_const(j_nonobject);
CHECK(j_nonobject.contains("foo") == false);
CHECK(j_nonobject_const.contains("foo") == false);
}

SECTION("boolean")
{
json j_nonobject(json::value_t::boolean);
const json j_nonobject_const(j_nonobject);
CHECK(j_nonobject.contains("foo") == false);
CHECK(j_nonobject_const.contains("foo") == false);
}

SECTION("number (integer)")
{
json j_nonobject(json::value_t::number_integer);
const json j_nonobject_const(j_nonobject);
CHECK(j_nonobject.contains("foo") == false);
CHECK(j_nonobject_const.contains("foo") == false);
}

SECTION("number (unsigned)")
{
json j_nonobject(json::value_t::number_unsigned);
const json j_nonobject_const(j_nonobject);
CHECK(j_nonobject.contains("foo") == false);
CHECK(j_nonobject_const.contains("foo") == false);
}

SECTION("number (floating-point)")
{
json j_nonobject(json::value_t::number_float);
const json j_nonobject_const(j_nonobject);
CHECK(j_nonobject.contains("foo") == false);
CHECK(j_nonobject_const.contains("foo") == false);
}
}
}
}
}

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