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json/docs/mkdocs/docs/examples/basic_json_view__materialize.cpp
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Niels Lohmann 330fbead59 Document clang-tidy exclusions, drop unneeded ones, and clean up doc examples (#5909)
* Document clang-tidy exclusions and drop unneeded ones

Re-enable every excluded check in a run of clang-tidy 22 over all tests
and remove the seven that never fire (cert-err58-cpp,
clang-analyzer-webkit.NoUncountedMemberChecker,
cppcoreguidelines-virtual-class-destructor, google-readability-function-size,
hicpp-function-size, hicpp-no-assembler, readability-function-size).

Document the reason for every remaining exclusion at the top of the file.

Exclude in advance the checks that only exist in clang-tidy 23 and are
noise here (bugprone-signed-bitwise, *-explicit-constructor,
readability-trailing-comma, modernize-use-string-view), plus
modernize-use-integer-sign-comparison, which needs C++20 std::cmp_less
and flags deliberate casts.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Fix clang-tidy findings in documentation examples and replace redundant aliases

Apply clang-tidy fixes to the documentation examples:
- performance-avoid-endl: std::endl -> '\n'
- readability-qualified-auto: auto -> auto* / const auto*
- performance-for-range-copy: copy -> const reference
- google-readability-casting: C-style cast -> static_cast

Replace redundant aliases (readability-redundant-qualified-alias) such as
"using json = nlohmann::json;" with "using nlohmann::json;" in the
documentation, README, examples, tests, and benchmarks. Aliases at class
scope and aliases of other types (with_base_class_t etc.) are kept.

No changes to the library or its public API. All changed examples were
compiled and run; their output matches the stored .output files (except
max_size and meta, which depend on the platform and compiler).

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Format doc examples with the pinned astyle

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-25 12:07:51 +01:00

34 lines
1.2 KiB
C++

#include <array>
#include <iostream>
#include <nlohmann/json_view.hpp>
using nlohmann::json_document;
int main()
{
// three incoming messages; skip the ones that are not useful without ever
// building a nlohmann::json value for them
json_document heartbeat = json_document::parse("null");
json_document empty_batch = json_document::parse("[]");
json_document batch = json_document::parse(R"([{"id": 1}, {"id": 2}, {"id": 3}])");
std::array<const json_document*, 3> messages = {{&heartbeat, &empty_batch, &batch}};
for (const json_document* d : messages)
{
// is_array()/empty() only look at the flat index: a discarded
// heartbeat or an empty batch is never turned into a nlohmann::json
// value, so no per-element allocation happens for them
if (!d->root().is_array() || d->root().empty())
{
std::cout << "skipped\n";
continue;
}
// materialize() replays the subtree through the same SAX builder
// basic_json::parse() uses, so the result is exactly what
// basic_json::parse() would have produced for the same text
nlohmann::json value = d->root().materialize();
std::cout << value.dump() << '\n';
}
}