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json/docs/mkdocs/docs/examples/basic_json_document__read.cpp
T
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

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#include <iostream>
#include <string>
#include <vector>
#include <nlohmann/json_view.hpp>
using nlohmann::json_document;
int main()
{
std::cout << std::boolalpha;
std::vector<std::string> messages =
{
R"({"id": 1})", R"({"id": 2, "tag": "x"})", R"({"id": 3})"
};
// parse into the same document over and over: its node index and decode
// buffer are reused instead of being freed and reallocated for each message
json_document doc;
std::size_t total = 0;
for (const auto& msg : messages)
{
doc.read(msg);
total += doc.root().size();
}
std::cout << total << '\n';
// read() can also change what kind of input is owned/borrowed between calls
doc.read(std::string(R"({"owned": true})"));
std::cout << doc.owns_source() << '\n';
}