Publisher

In this course, we'll be building out components of "Peril" - a make-believe clone of the classic game "Risk". The only difference is that it's online and real-time!

Pub/Sub (publish/subscribe) systems are particularly useful when many events are happening in real-time and disparate parts of the system need to react to those events.

Assignment

While Pub/Sub is an architecture that often refers to messages being sent between programs, or sometimes even between machines on a network, let's start with a simple pub/sub system that runs in a single program.

In "Peril", users control armies, represented as a slice of pieces: []piece. When a piece moves to a location that contains a piece owned by another player, a battle occurs. Whenever a player makes a "move", we need to publish a message telling the game that a move has occurred.

Read the doBattles function. Note that it's expecting messages to come in from the publishCh channel.

Complete the march method. It should publish a move message to the publishCh channel.

package main

func (u user) march(p piece, publishCh chan<- move) {

// ?

}

// don't touch below this line

type user struct {

name string

pieces []piece

}

type move struct {

userName string

piece piece

}

type piece struct {

location string

name string

}

func doBattles(publishCh <-chan move, users []user) []piece {

fights := []piece{}

for mv := range publishCh {

for _, u := range users {

if u.name == mv.userName {

continue

}

for _, piece := range u.pieces {

if piece.location == mv.piece.location {

fights = append(fights, piece)

}