NisseBolt

A C++ library for building Slack bots, modeled after the Slack Bolt for Python API. If you've used Bolt in Python, NisseBolt should feel familiar — register handlers for messages, commands, actions, and views with the same mental model, but in modern C++20.

Why?

The Slack Bolt API is a well-designed interface for building bots. But if your infrastructure is C++ and you want type-safe, zero-boilerplate serialization with async IO, rewriting in Python isn't ideal. NisseBolt brings the Bolt programming model to C++ while leveraging the ThorsAnvil ecosystem — automatic JSON serialization, coroutine-based async networking, and hot-reloadable plugin architecture.

Quick Example

#include "NisseBolt/App.h"

namespace Bolt = ThorsAnvil::Nisse::Bolt;

struct MyBot: Bolt::App
{
    MyBot(Bolt::AppConfig const& config, std::string const& slot)
        : App(config, slot)
    {
        // Respond to messages containing "hello"
        message("hello", [](auto const& event, auto const& say) {
            say("Hey there!");
        });

        // Handle a slash command
        command("/greet", [](auto const& ack, auto const& response, auto const& cmd) {
            ack("Greetings!");
        });

        // Handle a button click
        action("approve_button", [](auto const& ack, auto const& response, auto const& action, auto const& value) {
            ack();
        });
    }
};

THORS_ANVIL_NISSE_BOLT_SERVER_INIT(Bolt::AppConfig, MyBot);

Core Concepts

Concept	Description
App	Your bot. Subclass it and register handlers in the constructor.
Say	Send messages back to a channel. Supports plain text and Block Kit.
Ack	Acknowledge an incoming request from Slack (slash commands, actions, views).
View	Open, push, or update Slack modals with submit/close handlers.

Handler Types

• message(filter, handler) — React to messages. Filter by string, regex, or custom predicate.
• event<T>(handler) — Handle any Slack event type (app mentions, reactions, file uploads, etc.).
• command(name, handler) — Respond to slash commands like /greet.
• action(actionId, handler) — Handle interactive components (buttons, menus, etc.).
• viewOpen / viewPush / viewUpdate — Manage Slack modals.

Part of ThorsAnvil

NisseBolt is a component of the ThorsAnvil monorepo. It builds on:

• ThorsSerializer — Automatic JSON/YAML/BSON serialization via compile-time traits. All Slack API types are serialized without hand-written code.
• Nisse — Coroutine-based async HTTP server. Your handlers read like synchronous code while running on an event loop.
• Mug — Hot-reloadable plugin server. Your bot compiles to a shared library that Mug loads, monitors, and reloads on change — no server restart needed.

Documentation

• API Reference: loki-astari.github.io/ThorsAnvil/NisseBolt.html

Article Series

A detailed walkthrough covering setup, configuration, and building a complete Slack bot:

1. Mug: The Plugin Server — How the hot-reloadable plugin architecture works.
2. SlackMug: Connecting to Slack — Setting up a Slack app and wiring it to NisseBolt.
3. SlackHandlers: Messages & Commands — Handling messages and slash commands.
4. SlackAction: Interactive Components — Buttons, menus, and user actions.
5. SlackView: Modals — Opening and managing Slack modals.

Installing

The simplest way to install is via Homebrew:

brew install thors-anvil

Or build from source:

git clone --recurse-submodules https://github.com/Loki-Astari/ThorsAnvil.git
cd ThorsAnvil
./configure
make
make install

Requirements

• C++20 compiler
• Boost (>= 1.70, for Coroutine2)
• OpenSSL
• libevent

See the ThorsAnvil README for full build instructions and platform notes.

Using in Your Project

Once ThorsAnvil is installed, CMake config files are available automatically.

CMake

find_package(ThorsAnvil REQUIRED)

add_library(mybot MODULE mybot.cpp)
target_link_libraries(mybot ThorsAnvil::NisseBolt)

All transitive dependencies (ThorsAnvil::ThorsSlack, ThorsAnvil::Nisse, ThorsAnvil::ThorSerialize, etc.) are pulled in automatically.

Make

CXXFLAGS += -std=c++20 -I$(shell brew --prefix thors-anvil)/include
LDFLAGS  += -L$(shell brew --prefix thors-anvil)/lib
LDLIBS   += -lNisseBolt -lNisse -lThorSerialize -lThorsSocket -lThorsLogging

mybot.so: mybot.cpp
	$(CXX) -shared $(CXXFLAGS) $(LDFLAGS) $< $(LDLIBS) -o $@