How to add library to C++ Project using homebrew, cMake and, cLion - c++

Question

I am really new to C++ and I am a bit confused.
I am trying to add this lib to my project (https://github.com/mrtazz/restclient-cpp).
I have installed it using Homebrew
brew tap mrtazz/oss
brew install restclient-cpp
then I tried adding the library to my CMakeLists by including and linking the Homebrew install directories.
CMakeLists.txt
cmake_minimum_required(VERSION 3.15)
project(POS)
set(CMAKE_CXX_STANDARD 14)
include_directories(/usr/local/include)
link_directories(/usr/local/lib)
add_library(
restclient-cpp STATIC
connection.h
helpers.h
restclient.h
version.h
)
add_executable(POS main.cpp program.cpp program.h programs/find.cpp programs/find.h tools/db.cpp tools/db.h)
target_link_libraries(POS PUBLIC restclient-cpp)
then I get this error...
CMake Error at CMakeLists.txt:16 (add_library):
Cannot find source file:
connection.h
Tried extensions .c .C .c++ .cc .cpp .cxx .cu .m .M .mm .h .hh .h++ .hm
.hpp .hxx .in .txx
CMake Error at CMakeLists.txt:16 (add_library):
No SOURCES given to target: restclient-cpp
I know something is wrong with the directories but I just cannot figure it out, I would greatly appreciate as much information as possible. I'm just trying to have some fun with this and I cannot figure out why I cannot add this simple library to my build.
Thank you.

Answer 1

You are trying to add header files to the add_library command. Those files need to be in a directory that you include via include_directory. You also should not put header files into the add_executable command.
To link an existing library you can call target_link_libraries.
example:
include_directories(${MY_INCLUDE_DIRS})
add_executable(main source.cpp)
target_link_libraries(main extlib)
It's probably best to find a simple CMake setup and try to use it as template.