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Getting started

As an example, let's start with one of the most popular C++ libraries: POCO.

We will use CMake. Even though it is not a conan requirement, it is very convenient.

A Timer using POCO libraries

First, let's create a folder for our project:

$ mkdir mytimer
$ cd mytimer

Note

if you have the code in a github repository, instead of creating the folder, you can just clone the project

$ git clone https://github.com/memsharded/example-poco-timer.git mytimer

Create the following source files inside that folder :

timer.cpp

// $Id: //poco/1.4/Foundation/samples/Timer/src/Timer.cpp#1 $
// This sample demonstrates the Timer and Stopwatch classes.
// Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
// SPDX-License-Identifier:     BSL-1.0

#include "Poco/Timer.h"
#include "Poco/Thread.h"
#include "Poco/Stopwatch.h"
#include <iostream>

using Poco::Timer;
using Poco::TimerCallback;
using Poco::Thread;
using Poco::Stopwatch;

class TimerExample{
public:
        TimerExample(){ _sw.start();}

        void onTimer(Timer& timer){
                std::cout << "Callback called after " << _sw.elapsed()/1000 << " milliseconds." << std::endl;
        }
private:
        Stopwatch _sw;
};

int main(int argc, char** argv){
        TimerExample example;
        Timer timer(250, 500);
        timer.start(TimerCallback<TimerExample>(example, &TimerExample::onTimer));

        Thread::sleep(5000);
        timer.stop();
        return 0;
}

Now, also create a conanfile.txt inside the same folder with the following content:

conanfile.txt

[requires]
Poco/1.7.3@lasote/stable

[generators]
cmake

In this example we will use cmake to build the project, which is why the cmake generator is specified, but please feel free to use any other build system. This generator will create a conanbuildinfo.cmake file that defines cmake variables as include paths and library names, that can be used in our build.

Note

If you are not a cmake user, change the [generators] section of your conanfile.txt to gcc or a more generic one txt to handle requirements with any build system. Learn more in :ref:`Using packages<manage_deps>`

Just include the generated file and use those variables inside our own CMakeLists.txt:

CMakeLists.txt

project(FoundationTimer)
cmake_minimum_required(VERSION 2.8.12)

include(${CMAKE_BINARY_DIR}/conanbuildinfo.cmake)
conan_basic_setup()

add_executable(timer timer.cpp)
target_link_libraries(timer ${CONAN_LIBS})

Building the timer example

Lets create a build folder, so temporary build files are put there, and install the requirements (pointing to the parent directory, as it is where the conanfile.txt is):

$ mkdir build && cd build
$ conan install ..

This install command will download the binary package required for your configuration (detected the first time that you ran the conan command), together with other required libraries, like OpenSSL and Zlib. It will also create the conanbuildinfo.cmake file in the current directory, in which you can see the cmake defined variables, and a conaninfo.txt where information about settings, requirements and options is saved.

Warning

There are binaries for several compilers, like Visual Studio 12, 14, linux-gcc 4.9 and apple-clang 3.5. If you are using another setup, the command might fail because of the missing package. You could try to change your settings or build it from source, using the --build missing option, instead of retrieving the binaries. Such a build might not have been tested and eventually fail. OpenSSL requires perl and some specific tools to build from source.

Now, you are ready to build and run your project:

(win)
$ cmake .. -G "Visual Studio 14 Win64"
$ cmake --build . --config Release

(linux, mac)
$ cmake .. -G "Unix Makefiles" -DCMAKE_BUILD_TYPE=Release
$ cmake --build .
...
[100%] Built target timer
$ ./bin/timer
Callback called after 250 milliseconds.
...

Inspecting dependencies

The retrieved packages have been installed to your local user cache (typically .conan/data), so they can be reused from there in other projects, and allow to clean your current project and keep working even without network connection. To search packages in the local cache you can do:

$ conan search

Please check the reference for more information on how to search in remotes, or how to remove or clean packages from the local cache, or how to define custom cache directory per user or per project.

You can also inspect your current projects dependencies with the info command, pointing it to the folder where the conanfile.txt is:

$ conan info ..

Building with other configurations

Let's try building your timer project with a different configuration. For example, you could try building the 32 bits version.

  • The first time you run the conan command, your settings will be detected (compiler, architecture...) automatically.
  • You can change your default settings by editing the ~/.conan/conan.conf file
  • You can always override the default settings in install command with the -s parameter. Example:
$ conan install -s arch=x86 -s compiler=gcc -s compiler.version=4.9
  • You should install a different package, using the -s arch=x86 setting , instead of the default used previously, that in most cases will be x86_64
  • You will also have to change your project build:
    • In Windows, change the cmake invocation accordingly to Visual Studio 14
    • In Linux, you have to add the -m32 flag to your CMakeLists.txt: SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -m32"), and the same to CMAKE_C_FLAGS, CMAKE_SHARED_LINK_FLAGS and CMAKE_EXE_LINKER_FLAGS. This can also be done more easily, automatically with conan, as we'll see later.
    • In Mac, you need to add the definition -DCMAKE_OSX_ARCHITECTURES=i386

Got any doubts? Please check out our :ref:`FAQ section <faq>` or write to us.