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modern-cmake/chapters/projects/fetch.md
Henry Fredrick Schreiner ed2227e7a4 Updates to FetchContent
2018-04-05 13:01:02 +02:00

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#FetchContent (CMake 3.11+)
Often, you would like to do your download of data or packages as part of the configure instead of the build. This was invented several times in third party modules, but was finally added to CMake itself as part of CMake 3.11 as the [FetchContent] module.
The [FetchContent] module has excellent documentation that I won't try to repeat. The key ideas are:
* Use `FetchContent_Declare(MyName` to get data or a package. You can set URLs, Git repositories, and more.
* Use `FetchContent_GetProperties(MyName)` on the name you picked in the first step to get `MyName_*` variables.
* Check `MyName_POPULATED`, and if not populated, use `FetchContent_Populate(MyName)` (and if a package, `add_subdirectory("${MyName_SOURCE_DIR}" "${MyName_SOURCE_DIR}")`)
For example, to download Catch2:
```cmake
FetchContent_Declare(
catch
GIT_REPOSITORY https://github.com/catchorg/Catch2.git
GIT_TAG v2.2.1
)
FetchContent_GetProperties(catch)
if(NOT catch_POPULATED)
FetchContent_Populate(catch)
add_subdirectory(${catch_SOURCE_DIR} ${catch_BINARY_DIR})
endif()
```
[FetchContent]: https://cmake.org/cmake/help/latest/module/FetchContent.html