IMPLEMENT_HANDLER.md

Implement a Handler module

In this guide we will learn how to implement a Handler module which is a type of module that allows us to generate an HTTP response from a request.

IHandlerModule interface

Let's look at the definition of the IHandlerModule interface.

class IHandlerModule : public IModule {
public:
    virtual void Handle(http::Request &req, http::Response &res) = 0;

    [[nodiscard]] virtual double GetHandlerPriority() const noexcept = 0;

    [[nodiscard]] virtual bool ShouldHandle(const http::Context &ctx, const http::Request &req) const = 0;
};

We have three methods to implement, let's go!

❗ Don't forget to implement the IModule methods

Create a handler

Okay, let's create our own class which inherits from IHandlerModule.

#include "ziapi/Module.hpp"

class MyHandler : public ziapi::IHandlerModule {
public:
    void Handle(http::Context &ctx, const http::Request &req, http::Response &res) override;

    [[nodiscard]] double GetHandlerPriority() const noexcept override;

    [[nodiscard]] bool ShouldHandle(const http::Context &ctx, const http::Request &req) const override;
};

Then, let's implement the GetHandlerPriority(). Our module doesn't have specific priority requirements so we'll put it at 0.5f.

[[nodiscard]] double MyHandler::GetHandlerPriority() const noexcept
{
    return 0.5f;
}

Then, let's implement the ShouldHandle(). This method is invoked to know if our handler should be called for a specific request. We can return true if we want all requests to go through this handler but let's just say our handler only handles GET request for the sake of the example.

[[nodiscard]] bool MyHandler::ShouldHandle(const http::Context &ctx, const http::Request &req) const
{
    return req.method == http::method::kGet;
}

Great! Now our handler will be called on all GET requests! Now let's add the Handle().

void MyHandler::Handle(http::Context &ctx, const http::Request &req, http::Response &res)
{
    res.status_code = 200;
    res.body = "Hello guys!";
}

And that's it! You now have a module which displays "Hello guys!" in your browser upon all GET requests.