How to include in an external project

[hect1995]

• Describe what you want to achieve.
  I want to import the json functionality to my own project

• Describe what you tried.
  Following the README, I have cloned this repo in an external folder not in the path of mine and in my CMake I do:

find_package(nlohmann_json 3.2.0 REQUIRED)
add_library(${BINARY}_lib nlohmann_json::nlohmann_json)
target_link_libraries(${BINARY}_lib PRIVATE nlohmann_json::nlohmann_json)

But get this output:

CMake Error at HackerRank/CMakeLists.txt:7 (find_package):
  By not providing "Findnlohmann_json.cmake" in CMAKE_MODULE_PATH this
  project has asked CMake to find a package configuration file provided by
  "nlohmann_json", but CMake did not find one.

  Could not find a package configuration file provided by "nlohmann_json"
  (requested version 3.2.0) with any of the following names:

    nlohmann_jsonConfig.cmake
    nlohmann_json-config.cmake

  Add the installation prefix of "nlohmann_json" to CMAKE_PREFIX_PATH or set
  "nlohmann_json_DIR" to a directory containing one of the above files.  If
  "nlohmann_json" provides a separate development package or SDK, be sure it
  has been installed.

Sorry in advance for the question but would be much appreciated if you could help me.

• Describe which system (OS, compiler) you are using.
  Mac OS Catalina and LLDB

• Describe which version of the library you are using (release version, develop branch).
  I cloned the latest master

[nlohmann]

Did you install the library? This is required if you want to find it via find_package.

[hect1995]

Yes installed but I have one doubt. Once it is installed with Homebrew, then in my CMake I need to add:

# CMakeLists.txt
find_package(nlohmann_json 3.2.0 REQUIRED)
...
add_library(foo ...)
...
target_link_libraries(foo PRIVATE nlohmann_json::nlohmann_json)

what is what goes in the ... inside add_library?

[nlohmann]

I could do the following:

brew tap nlohmann/json
brew install nlohmann-json

and the following project:

cmake_minimum_required(VERSION 3.1)

project(DummyProject CXX)

find_package(nlohmann_json 3.2.0 REQUIRED)
add_executable(dummy dummy.cpp)
target_link_libraries(dummy PRIVATE nlohmann_json::nlohmann_json)

#include <nlohmann/json.hpp>
#include <iostream>

int main()
{
    std::cout << nlohmann::json::meta() << std::endl;
}

can be configured via:

$ cmake ..
-- The CXX compiler identification is AppleClang 11.0.3.11030032
-- Check for working CXX compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++
-- Check for working CXX compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++ - works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found nlohmann_json: /usr/local/lib/cmake/nlohmann_json/nlohmann_jsonConfig.cmake (found suitable version "3.7.3", minimum required is "3.2.0") 
-- Configuring done
-- Generating done
-- Build files have been written to: /Users/niels/Desktop/foo/build

and build with

$  make
Scanning dependencies of target dummy
[ 50%] Building CXX object CMakeFiles/dummy.dir/dummy.cpp.o
[100%] Linking CXX executable dummy
[100%] Built target dummy

$ ./dummy
{"compiler":{"c++":"201103","family":"clang","version":"11.0.3 (clang-1103.0.32.59)"},"copyright":"(C) 2013-2017 Niels Lohmann","name":"JSON for Modern C++","platform":"apple","url":"https://github.com/nlohmann/json","version":{"major":3,"minor":7,"patch":3,"string":"3.7.3"}}

[hect1995]

You are right, thank @nlohmann . I know it does not concern you as it is a problem from my side but I have In my project one general CMake and one other inside the subproject. With this I get the error:
/Users/hectoresteban/Documents/C++/C++Projects/DailyCoding/HackerRank/read_json_file.cpp:1:10: fatal error: 'nlohmann/json.hpp' file not found
This is my CMake in the main directory:

cmake_minimum_required(VERSION 3.15)
project(DailyCoding)
set(CMAKE_CXX_STANDARD 17)
include_directories(HackerRank) # points where I build everything
find_package(nlohmann_json 3.2.0 REQUIRED)
add_subdirectory(HackerRank)

An this is the CMake in HackerRank where I include your package:

set(BINARY ${CMAKE_PROJECT_NAME})
set(SOURCES read_json_file.cpp)
add_executable(${BINARY}_run ${SOURCES})
add_library(${BINARY}_lib STATIC ${SOURCES})
target_link_libraries(${BINARY}_run PRIVATE nlohmann_json::nlohmann_json)

Do you know what is the reason why with this structure happens this error?

Thank a lot

[nlohmann]

How does read_json_file.cpp:1:10 look like?

[hect1995]

#include <nlohmann/json.hpp>

[nlohmann]

Are there errors or warning running CMake?