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mirror of https://github.com/nlohmann/json.git synced 2025-08-09 05:22:48 +03:00

📝 add mkdocs

This commit is contained in:
Niels Lohmann
2020-05-24 13:03:04 +02:00
parent c92a696852
commit a8f0cd15df
36 changed files with 2656 additions and 261 deletions

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# CMake
You can also use the `nlohmann_json::nlohmann_json` interface target in CMake. This target populates the appropriate usage requirements for `INTERFACE_INCLUDE_DIRECTORIES` to point to the appropriate include directories and `INTERFACE_COMPILE_FEATURES` for the necessary C++11 flags.
## External
To use this library from a CMake project, you can locate it directly with `find_package()` and use the namespaced imported target from the generated package configuration:
```cmake
# CMakeLists.txt
find_package(nlohmann_json 3.2.0 REQUIRED)
...
add_library(foo ...)
...
target_link_libraries(foo PRIVATE nlohmann_json::nlohmann_json)
```
The package configuration file, `nlohmann_jsonConfig.cmake`, can be used either from an install tree or directly out of the build tree.
## Embedded
To embed the library directly into an existing CMake project, place the entire source tree in a subdirectory and call `add_subdirectory()` in your `CMakeLists.txt` file:
```cmake
# Typically you don't care so much for a third party library's tests to be
# run from your own project's code.
set(JSON_BuildTests OFF CACHE INTERNAL "")
# If you only include this third party in PRIVATE source files, you do not
# need to install it when your main project gets installed.
# set(JSON_Install OFF CACHE INTERNAL "")
# Don't use include(nlohmann_json/CMakeLists.txt) since that carries with it
# unintended consequences that will break the build. It's generally
# discouraged (although not necessarily well documented as such) to use
# include(...) for pulling in other CMake projects anyways.
add_subdirectory(nlohmann_json)
...
add_library(foo ...)
...
target_link_libraries(foo PRIVATE nlohmann_json::nlohmann_json)
```
## Embedded (FetchContent)
Since CMake v3.11,
[FetchContent](https://cmake.org/cmake/help/v3.11/module/FetchContent.html) can
be used to automatically download the repository as a dependency at configure type.
Example:
```cmake
include(FetchContent)
FetchContent_Declare(json
GIT_REPOSITORY https://github.com/nlohmann/json
GIT_TAG v3.7.3)
FetchContent_GetProperties(json)
if(NOT json_POPULATED)
FetchContent_Populate(json)
add_subdirectory(${json_SOURCE_DIR} ${json_BINARY_DIR} EXCLUDE_FROM_ALL)
endif()
target_link_libraries(foo PRIVATE nlohmann_json::nlohmann_json)
```
!!! Note
The repository <https://github.com/nlohmann/json> download size is huge.
It contains all the dataset used for the benchmarks. You might want to depend on
a smaller repository. For instance, you might want to replace the URL above by
<https://github.com/ArthurSonzogni/nlohmann_json_cmake_fetchcontent>.
## Supporting Both
To allow your project to support either an externally supplied or an embedded JSON library, you can use a pattern akin to the following:
``` cmake
# Top level CMakeLists.txt
project(FOO)
...
option(FOO_USE_EXTERNAL_JSON "Use an external JSON library" OFF)
...
add_subdirectory(thirdparty)
...
add_library(foo ...)
...
# Note that the namespaced target will always be available regardless of the
# import method
target_link_libraries(foo PRIVATE nlohmann_json::nlohmann_json)
```
```cmake
# thirdparty/CMakeLists.txt
...
if(FOO_USE_EXTERNAL_JSON)
find_package(nlohmann_json 3.2.0 REQUIRED)
else()
set(JSON_BuildTests OFF CACHE INTERNAL "")
add_subdirectory(nlohmann_json)
endif()
...
```
`thirdparty/nlohmann_json` is then a complete copy of this source tree.

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project(json_example)
cmake_minimum_required(VERSION 2.8.12)
add_definitions("-std=c++11")
include(${CMAKE_BINARY_DIR}/conanbuildinfo.cmake)
conan_basic_setup()
add_executable(json_example example.cpp)
target_link_libraries(json_example ${CONAN_LIBS})

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[requires]
nlohmann_json/3.7.3
[generators]
cmake

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#include <nlohmann/json.hpp>
#include <iostream>
using json = nlohmann::json;
int main()
{
std::cout << json::meta() << std::endl;
}

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#include <nlohmann/json.hpp>
#include <iostream>
using json = nlohmann::json;
int main()
{
std::cout << json::meta() << std::endl;
}

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# Integration
[`json.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json.hpp) is the single required file in `single_include/nlohmann` or [released here](https://github.com/nlohmann/json/releases). You need to add
```cpp
#include <nlohmann/json.hpp>
// for convenience
using json = nlohmann::json;
```
to the files you want to process JSON and set the necessary switches to enable C++11 (e.g., `-std=c++11` for GCC and Clang).
You can further use file [`include/nlohmann/json_fwd.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/json_fwd.hpp) for forward-declarations. The installation of json_fwd.hpp (as part of cmake's install step), can be achieved by setting `-DJSON_MultipleHeaders=ON`.

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# Package Managers
Throughout this page, we will describe how to compile the example file `example.cpp` below.
```cpp
--8<-- "integration/example.cpp"
```
## Homebrew
If you are using OS X and [Homebrew](http://brew.sh), just type
```sh
brew tap nlohmann/json
brew install nlohmann_json
```
and you're set. If you want the bleeding edge rather than the latest release, use
```sh
brew tap nlohmann/json
brew install nlohmann_json --HEAD
```
instead.
!!! example
1. Create the following file:
=== "example.cpp"
```cpp
--8<-- "integration/example.cpp"
```
2. Install the package
```sh
brew tap nlohmann/json
brew install nlohmann_json
```
3. Determine the include path, which defaults to `/usr/local/Cellar/nlohmann_json/$version/include`, where `$version` is the version of the library, e.g. `3.7.3`. The path of the library can be determined with
```sh
brew list nlohmann_json
```
4. Compile the code. For instance, the code can be compiled using Clang with
```sh
clang++ example.cpp -I/usr/local/Cellar/nlohmann_json/3.7.3/include -std=c++11 -o example
```
## Meson
If you are using the [Meson Build System](http://mesonbuild.com), add this source tree as a [meson subproject](https://mesonbuild.com/Subprojects.html#using-a-subproject). You may also use the `include.zip` published in this project's [Releases](https://github.com/nlohmann/json/releases) to reduce the size of the vendored source tree. Alternatively, you can get a wrap file by downloading it from [Meson WrapDB](https://wrapdb.mesonbuild.com/nlohmann_json), or simply use `meson wrap install nlohmann_json`. Please see the meson project for any issues regarding the packaging.
The provided meson.build can also be used as an alternative to cmake for installing `nlohmann_json` system-wide in which case a pkg-config file is installed. To use it, simply have your build system require the `nlohmann_json` pkg-config dependency. In Meson, it is preferred to use the [`dependency()`](https://mesonbuild.com/Reference-manual.html#dependency) object with a subproject fallback, rather than using the subproject directly.
## Conan
If you are using [Conan](https://www.conan.io/) to manage your dependencies, merely add `nlohmann_json/x.y.z` to your `conanfile`'s requires, where `x.y.z` is the release version you want to use. Please file issues [here](https://github.com/conan-io/conan-center-index/issues) if you experience problems with the packages.
!!! example
1. Create the following files:
=== "Conanfile.txt"
```ini
--8<-- "integration/conan/Conanfile.txt"
```
=== "CMakeLists.txt"
```cmake
--8<-- "integration/conan/CMakeLists.txt"
```
=== "example.cpp"
```cpp
--8<-- "integration/conan/example.cpp"
```
2. Build:
```sh
mkdir build
cd build
conan install ..
cmake ..
cmake --build .
```
## Spack
If you are using [Spack](https://www.spack.io/) to manage your dependencies, you can use the [`nlohmann-json` package](https://spack.readthedocs.io/en/latest/package_list.html#nlohmann-json). Please see the [spack project](https://github.com/spack/spack) for any issues regarding the packaging.
## Hunter
If you are using [hunter](https://github.com/cpp-pm/hunter) on your project for external dependencies, then you can use the [nlohmann_json package](https://hunter.readthedocs.io/en/latest/packages/pkg/nlohmann_json.html). Please see the hunter project for any issues regarding the packaging.
## Buckaroo
If you are using [Buckaroo](https://buckaroo.pm), you can install this library's module with `buckaroo add github.com/buckaroo-pm/nlohmann-json`. Please file issues [here](https://github.com/buckaroo-pm/nlohmann-json). There is a demo repo [here](https://github.com/njlr/buckaroo-nholmann-json-example).
## vcpkg
If you are using [vcpkg](https://github.com/Microsoft/vcpkg/) on your project for external dependencies, then you can use the [nlohmann-json package](https://github.com/Microsoft/vcpkg/tree/master/ports/nlohmann-json). Please see the vcpkg project for any issues regarding the packaging.
## cget
If you are using [cget](http://cget.readthedocs.io/en/latest/), you can install the latest development version with `cget install nlohmann/json`. A specific version can be installed with `cget install nlohmann/json@v3.1.0`. Also, the multiple header version can be installed by adding the `-DJSON_MultipleHeaders=ON` flag (i.e., `cget install nlohmann/json -DJSON_MultipleHeaders=ON`).
## CocoaPods
If you are using [CocoaPods](https://cocoapods.org), you can use the library by adding pod `"nlohmann_json", '~>3.1.2'` to your podfile (see [an example](https://bitbucket.org/benman/nlohmann_json-cocoapod/src/master/)). Please file issues [here](https://bitbucket.org/benman/nlohmann_json-cocoapod/issues?status=new&status=open).
## NuGet
If you are using [NuGet](https://www.nuget.org), you can use the package [nlohmann.json](https://www.nuget.org/packages/nlohmann.json/). Please check [this extensive description](https://github.com/nlohmann/json/issues/1132#issuecomment-452250255) on how to use the package. Please files issues [here](https://github.com/hnkb/nlohmann-json-nuget/issues).
## Conda
If you are using [conda](https://conda.io/), you can use the package [nlohmann_json](https://github.com/conda-forge/nlohmann_json-feedstock) from [conda-forge](https://conda-forge.org) executing `conda install -c conda-forge nlohmann_json`. Please file issues [here](https://github.com/conda-forge/nlohmann_json-feedstock/issues).
## MSYS2
If you are using [MSYS2](http://www.msys2.org/), your can use the [mingw-w64-nlohmann-json](https://packages.msys2.org/base/mingw-w64-nlohmann-json) package, just type `pacman -S mingw-w64-i686-nlohmann-json` or `pacman -S mingw-w64-x86_64-nlohmann-json` for installation. Please file issues [here](https://github.com/msys2/MINGW-packages/issues/new?title=%5Bnlohmann-json%5D) if you experience problems with the packages.
## build2
If you are using [`build2`](https://build2.org), you can use the [`nlohmann-json`](https://cppget.org/nlohmann-json) package from the public repository http://cppget.org or directly from the [package's sources repository](https://github.com/build2-packaging/nlohmann-json). In your project's `manifest` file, just add `depends: nlohmann-json` (probably with some [version constraints](https://build2.org/build2-toolchain/doc/build2-toolchain-intro.xhtml#guide-add-remove-deps)). If you are not familiar with using dependencies in `build2`, [please read this introduction](https://build2.org/build2-toolchain/doc/build2-toolchain-intro.xhtml).
Please file issues [here](https://github.com/build2-packaging/nlohmann-json) if you experience problems with the packages.
## wsjcpp
If you are using [`wsjcpp`](http://wsjcpp.org), you can use the command `wsjcpp install "https://github.com/nlohmann/json:develop"` to get the latest version. Note you can change the branch ":develop" to an existing tag or another branch.