I'm trying to code in C++ (C++11) a very simple example according to the Clean Architecture concept described by Uncle Bob Martin here (picture below):
The idea is to read some text by a Controller and print it by a Presenter. I have done something but it doesn't look like it's following the clean flow and the DIP of the blog post.
Among other things, I think the flow is wrong as, for example, the IUseCaseInputPort needs to know about the IUseCaseOutputPort (the read function has the IUseCaseOutputPort as input parameter, creating thus another dependency...).
I would really appreciate if someone could give me some tips about the best way to implement this. Many thanks in advance.
#include <iostream>
#include <string>
#include <memory>
class IUseCaseOutputPort {
public:
virtual void print(std::string message) = 0;
virtual ~IUseCaseOutputPort() {};
};
// 2 Presenters
class HtmlPresenter: public IUseCaseOutputPort {
public:
void print(std::string message) {
std::cout << "<p>" << message << "</p>" << std::endl;
}
};
class TextPresenter: public IUseCaseOutputPort {
public:
void print(std::string message) {
std::cout << message << std::endl;
}
};
//
class IUseCaseInputPort {
public:
virtual void read(std::shared_ptr<IUseCaseOutputPort> output) = 0;
virtual ~IUseCaseInputPort(){};
};
// specific UseCaseInteractor
class UseCaseInteractorForInputFromStdIn: public IUseCaseInputPort {
public:
void read(std::shared_ptr<IUseCaseOutputPort> output) {
std::string message;
std::cout << "Please input some text!";
std::getline(std::cin, message);
output->print(message);
}
};
// Controller
class ControllerToDisplayHtml {
public:
void displayInHtmlSomethingFromStdIn() {
input = std::make_shared<UseCaseInteractorForInputFromStdIn>();
std::shared_ptr<HtmlPresenter> output =
std::make_shared<HtmlPresenter>();
input->read(output);
}
private:
std::shared_ptr<IUseCaseInputPort> input;
};
int main() {
ControllerToDisplayHtml c;
c.displayInHtmlSomethingFromStdIn();
return 0;
}
For those interested, a complement to my question as suggested by BЈовић. Very simple example. Just to show the flow of this model.
#include <iostream>
#include <string>
#include <memory>
#include <fstream>
class IUseCaseOutputPort {
public:
virtual void print(std::string message) = 0;
virtual ~IUseCaseOutputPort() {};
};
// 2 Presenters
class HtmlPresenter: public IUseCaseOutputPort {
public:
void print(std::string message) {
std::cout << "<p>" << message << "</p>" << std::endl;
}
};
class TextPresenter: public IUseCaseOutputPort {
public:
void print(std::string message) {
std::cout << message << std::endl;
}
};
//
class IUseCaseInputPort {
public:
virtual std::string read() = 0;
virtual ~IUseCaseInputPort(){};
};
// specific UseCaseInteractor for reading text from the stdin
class UseCaseInteractorForInputFromStdIn: public IUseCaseInputPort {
public:
std::string read() {
std::string message;
std::cout << "Please input some text!" << std::endl;
std::getline(std::cin, message);
return message;
}
};
// specific UseCaseInteractor for reading text from a dummy file
class UseCaseInteractorForInputFromDummyFile: public IUseCaseInputPort {
public:
std::string read() {
const std::string filename = "/proc/meminfo";
std::string message = readFile(filename);
return message;
}
private:
std::string readFile(const std::string filename) {
std::string line;
std::string lines;
std::ifstream myfile(filename);
if (myfile.is_open()) {
while (myfile.good()) {
getline(myfile, line);
lines += line + '\n';
}
myfile.close();
} else {
lines = "Unable to open file";
}
return lines;
}
};
// Controller
class ControllerForReading {
public:
std::string readFromStdIn() {
input = std::make_shared<UseCaseInteractorForInputFromStdIn>();
std::string out = "This text was read from the stdin:\n";
out += input->read();
return out;
}
std::string readFromFile() {
input = std::make_shared<UseCaseInteractorForInputFromDummyFile>();
std::string out = "This text was read from the a file:\n";
out += input->read();
return out;
}
private:
std::shared_ptr<IUseCaseInputPort> input;
};
// main represents the outer shell
int main() {
std::cout << "Main started!" << std::endl;
ControllerForReading c;
const std::string textFromStdin = c.readFromStdIn();
const std::string textFromFile = c.readFromFile();
auto output = std::make_shared<HtmlPresenter>();
output->print(textFromStdin);
output->print(textFromFile);
auto output2 = std::make_shared<TextPresenter>();
output2->print(textFromStdin);
output2->print(textFromFile);
std::cout << "Main ended!" << std::endl;
return 0;
}
