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added items() function #874

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Niels Lohmann 2018-01-05 18:34:10 +01:00
parent 96b40b27a5
commit 78f8f837e6
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23
doc/examples/items.cpp Normal file
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@ -0,0 +1,23 @@
#include <iostream>
#include "json.hpp"
using json = nlohmann::json;
int main()
{
// create JSON values
json j_object = {{"one", 1}, {"two", 2}};
json j_array = {1, 2, 4, 8, 16};
// example for an object
for (auto& x : j_object.items())
{
std::cout << "key: " << x.key() << ", value: " << x.value() << '\n';
}
// example for an array
for (auto& x : j_array.items())
{
std::cout << "key: " << x.key() << ", value: " << x.value() << '\n';
}
}

1
doc/examples/items.link Normal file
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@ -0,0 +1 @@
<a target="_blank" href="https://wandbox.org/permlink/E7h0HOuw778Ski8S"><b>online</b></a>

7
doc/examples/items.output Normal file
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@ -0,0 +1,7 @@
key: one, value: 1
key: two, value: 2
key: 0, value: 1
key: 1, value: 2
key: 2, value: 4
key: 3, value: 8
key: 4, value: 16

62
src/json.hpp
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@ -11375,6 +11375,68 @@ class basic_json
return iteration_proxy<const_iterator>(ref);
}
/*!
@brief helper to access iterator member functions in range-based for
This function allows to access @ref iterator::key() and @ref
iterator::value() during range-based for loops. In these loops, a
reference to the JSON values is returned, so there is no access to the
underlying iterator.
For loop without `items()` function:
@code{cpp}
for (auto it = j_object.begin(); it != j_object.end(); ++it)
{
std::cout << "key: " << it.key() << ", value:" << it.value() << '\n';
}
@endcode
Range-based for loop without `items()` function:
@code{cpp}
for (auto it : j_object)
{
// "it" is of type json::reference and has no key() member
std::cout << "value: " << it << '\n';
}
@endcode
Range-based for loop with `items()` function:
@code{cpp}
for (auto it : j_object.items())
{
std::cout << "key: " << it.key() << ", value:" << it.value() << '\n';
}
@endcode
@note When iterating over an array, `key()` will return the index of the
element as string (see example).
@return iteration proxy object wrapping @a ref with an interface to use in
range-based for loops
@liveexample{The following code shows how the function is used.,items}
@exceptionsafety Strong guarantee: if an exception is thrown, there are no
changes in the JSON value.
@complexity Constant.
*/
iteration_proxy<iterator> items()
{
return iteration_proxy<iterator>(*this);
}
/*!
@copydoc items()
*/
iteration_proxy<const_iterator> items() const
{
return iteration_proxy<const_iterator>(*this);
}
/// @}

697
test/src/unit-iterator_wrapper.cpp
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@ -727,3 +727,700 @@ TEST_CASE("iterator_wrapper")
}
}
}
TEST_CASE("items()")
{
SECTION("object")
{
SECTION("value")
{
json j = {{"A", 1}, {"B", 2}};
int counter = 1;
for (auto i : j.items())
{
switch (counter++)
{
case 1:
{
CHECK(i.key() == "A");
CHECK(i.value() == json(1));
break;
}
case 2:
{
CHECK(i.key() == "B");
CHECK(i.value() == json(2));
break;
}
default:
{
break;
}
}
}
CHECK(counter == 3);
}
SECTION("reference")
{
json j = {{"A", 1}, {"B", 2}};
int counter = 1;
for (auto& i : j.items())
{
switch (counter++)
{
case 1:
{
CHECK(i.key() == "A");
CHECK(i.value() == json(1));
// change the value
i.value() = json(11);
CHECK(i.value() == json(11));
break;
}
case 2:
{
CHECK(i.key() == "B");
CHECK(i.value() == json(2));
// change the value
i.value() = json(22);
CHECK(i.value() == json(22));
break;
}
default:
{
break;
}
}
}
CHECK(counter == 3);
// check if values where changed
CHECK(j == json({{"A", 11}, {"B", 22}}));
}
SECTION("const value")
{
json j = {{"A", 1}, {"B", 2}};
int counter = 1;
for (const auto i : j.items())
{
switch (counter++)
{
case 1:
{
CHECK(i.key() == "A");
CHECK(i.value() == json(1));
break;
}
case 2:
{
CHECK(i.key() == "B");
CHECK(i.value() == json(2));
break;
}
default:
{
break;
}
}
}
CHECK(counter == 3);
}
SECTION("const reference")
{
json j = {{"A", 1}, {"B", 2}};
int counter = 1;
for (const auto& i : j.items())
{
switch (counter++)
{
case 1:
{
CHECK(i.key() == "A");
CHECK(i.value() == json(1));
break;
}
case 2:
{
CHECK(i.key() == "B");
CHECK(i.value() == json(2));
break;
}
default:
{
break;
}
}
}
CHECK(counter == 3);
}
}
SECTION("const object")
{
SECTION("value")
{
const json j = {{"A", 1}, {"B", 2}};
int counter = 1;
for (auto i : j.items())
{
switch (counter++)
{
case 1:
{
CHECK(i.key() == "A");
CHECK(i.value() == json(1));
break;
}
case 2:
{
CHECK(i.key() == "B");
CHECK(i.value() == json(2));
break;
}
default:
{
break;
}
}
}
CHECK(counter == 3);
}
SECTION("reference")
{
const json j = {{"A", 1}, {"B", 2}};
int counter = 1;
for (auto& i : j.items())
{
switch (counter++)
{
case 1:
{
CHECK(i.key() == "A");
CHECK(i.value() == json(1));
break;
}
case 2:
{
CHECK(i.key() == "B");
CHECK(i.value() == json(2));
break;
}
default:
{
break;
}
}
}
CHECK(counter == 3);
}
SECTION("const value")
{
const json j = {{"A", 1}, {"B", 2}};
int counter = 1;
for (const auto i : j.items())
{
switch (counter++)
{
case 1:
{
CHECK(i.key() == "A");
CHECK(i.value() == json(1));
break;
}
case 2:
{
CHECK(i.key() == "B");
CHECK(i.value() == json(2));
break;
}
default:
{
break;
}
}
}
CHECK(counter == 3);
}
SECTION("const reference")
{
const json j = {{"A", 1}, {"B", 2}};
int counter = 1;
for (const auto& i : j.items())
{
switch (counter++)
{
case 1:
{
CHECK(i.key() == "A");
CHECK(i.value() == json(1));
break;
}
case 2:
{
CHECK(i.key() == "B");
CHECK(i.value() == json(2));
break;
}
default:
{
break;
}
}
}
CHECK(counter == 3);
}
}
SECTION("array")
{
SECTION("value")
{
json j = {"A", "B"};
int counter = 1;
for (auto i : j.items())
{
switch (counter++)
{
case 1:
{
CHECK(i.key() == "0");
CHECK(i.value() == "A");
break;
}
case 2:
{
CHECK(i.key() == "1");
CHECK(i.value() == "B");
break;
}
default:
{
break;
}
}
}
CHECK(counter == 3);
}
SECTION("reference")
{
json j = {"A", "B"};
int counter = 1;
for (auto& i : j.items())
{
switch (counter++)
{
case 1:
{
CHECK(i.key() == "0");
CHECK(i.value() == "A");
// change the value
i.value() = "AA";
CHECK(i.value() == "AA");
break;
}
case 2:
{
CHECK(i.key() == "1");
CHECK(i.value() == "B");
// change the value
i.value() = "BB";
CHECK(i.value() == "BB");
break;
}
default:
{
break;
}
}
}
CHECK(counter == 3);
// check if values where changed
CHECK(j == json({"AA", "BB"}));
}
SECTION("const value")
{
json j = {"A", "B"};
int counter = 1;
for (const auto i : j.items())
{
switch (counter++)
{
case 1:
{
CHECK(i.key() == "0");
CHECK(i.value() == "A");
break;
}
case 2:
{
CHECK(i.key() == "1");
CHECK(i.value() == "B");
break;
}
default:
{
break;
}
}
}
CHECK(counter == 3);
}
SECTION("const reference")
{
json j = {"A", "B"};
int counter = 1;
for (const auto& i : j.items())
{
switch (counter++)
{
case 1:
{
CHECK(i.key() == "0");
CHECK(i.value() == "A");
break;
}
case 2:
{
CHECK(i.key() == "1");
CHECK(i.value() == "B");
break;
}
default:
{
break;
}
}
}
CHECK(counter == 3);
}
}
SECTION("const array")
{
SECTION("value")
{
const json j = {"A", "B"};
int counter = 1;
for (auto i : j.items())
{
switch (counter++)
{
case 1:
{
CHECK(i.key() == "0");
CHECK(i.value() == "A");
break;
}
case 2:
{
CHECK(i.key() == "1");
CHECK(i.value() == "B");
break;
}
default:
{
break;
}
}
}
CHECK(counter == 3);
}
SECTION("reference")
{
const json j = {"A", "B"};
int counter = 1;
for (auto& i : j.items())
{
switch (counter++)
{
case 1:
{
CHECK(i.key() == "0");
CHECK(i.value() == "A");
break;
}
case 2:
{
CHECK(i.key() == "1");
CHECK(i.value() == "B");
break;
}
default:
{
break;
}
}
}
CHECK(counter == 3);
}
SECTION("const value")
{
const json j = {"A", "B"};
int counter = 1;
for (const auto i : j.items())
{
switch (counter++)
{
case 1:
{
CHECK(i.key() == "0");
CHECK(i.value() == "A");
break;
}
case 2:
{
CHECK(i.key() == "1");
CHECK(i.value() == "B");
break;
}
default:
{
break;
}
}
}
CHECK(counter == 3);
}
SECTION("const reference")
{
const json j = {"A", "B"};
int counter = 1;
for (const auto& i : j.items())
{
switch (counter++)
{
case 1:
{
CHECK(i.key() == "0");
CHECK(i.value() == "A");
break;
}
case 2:
{
CHECK(i.key() == "1");
CHECK(i.value() == "B");
break;
}
default:
{
break;
}
}
}
CHECK(counter == 3);
}
}
SECTION("primitive")
{
SECTION("value")
{
json j = 1;
int counter = 1;
for (auto i : j.items())
{
++counter;
CHECK(i.key() == "");
CHECK(i.value() == json(1));
}
CHECK(counter == 2);
}
SECTION("reference")
{
json j = 1;
int counter = 1;
for (auto& i : j.items())
{
++counter;
CHECK(i.key() == "");
CHECK(i.value() == json(1));
// change value
i.value() = json(2);
}
CHECK(counter == 2);
// check if value has changed
CHECK(j == json(2));
}
SECTION("const value")
{
json j = 1;
int counter = 1;
for (const auto i : j.items())
{
++counter;
CHECK(i.key() == "");
CHECK(i.value() == json(1));
}
CHECK(counter == 2);
}
SECTION("const reference")
{
json j = 1;
int counter = 1;
for (const auto& i : j.items())
{
++counter;
CHECK(i.key() == "");
CHECK(i.value() == json(1));
}
CHECK(counter == 2);
}
}
SECTION("const primitive")
{
SECTION("value")
{
const json j = 1;
int counter = 1;
for (auto i : j.items())
{
++counter;
CHECK(i.key() == "");
CHECK(i.value() == json(1));
}
CHECK(counter == 2);
}
SECTION("reference")
{
const json j = 1;
int counter = 1;
for (auto& i : j.items())
{
++counter;
CHECK(i.key() == "");
CHECK(i.value() == json(1));
}
CHECK(counter == 2);
}
SECTION("const value")
{
const json j = 1;
int counter = 1;
for (const auto i : j.items())
{
++counter;
CHECK(i.key() == "");
CHECK(i.value() == json(1));
}
CHECK(counter == 2);
}
SECTION("const reference")
{
const json j = 1;
int counter = 1;
for (const auto& i : j.items())
{
++counter;
CHECK(i.key() == "");
CHECK(i.value() == json(1));
}
CHECK(counter == 2);
}
}
}