Asynchronous Operations

restcl provides built-in non-blocking asynchronous execution via sendAsync().

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Overview

When performing asynchronous HTTP operations, responses are processed via callback functions of type basic_callbacktype:

using basic_callbacktype = std::function<void(
    rest_request<>& request,
    std::expected<rest_response<>, int> responseOrError
)>;

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Usage Examples

Per-Request Callback

You can pass a lambda callback directly to sendAsync():

#include "siddiqsoft/restcl.hpp"

using namespace siddiqsoft;
using namespace siddiqsoft::restcl_literals;

void runAsyncRequest()
{
    auto client = GetRESTClient();

    auto req = "https://httpbin.org/get"_GET;

    client->sendAsync(std::move(req), [](auto& request, auto result) {
        if (result) {
            auto& resp = result.value();
            std::cout << "HTTP Status: " << resp.statusCode() << std::endl;
            std::cout << "Body: " << resp.content->body << std::endl;
        } else {
            std::cerr << "Error code: " << result.error() << std::endl;
        }
    });
}

Global Default Callback

You can also specify a default callback when initializing client configuration via configure() or GetRESTClient():

auto client = GetRESTClient(
    { {"userAgent", "AsyncClient/1.0"} },
    [](auto& req, auto result) {
        if (result) {
            std::cout << "Default callback received status: " << result->statusCode() << std::endl;
        }
    }
);

// Uses global default callback:
client->sendAsync("https://httpbin.org/get"_GET);

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Error Handling

sendAsync uses std::expected<rest_response<>, int> to represent either a successfully received HTTP response or a transport/network error code.

Checking Results

Always check if (result) or result.has_value() before dereferencing the response object.