{"id":5599,"date":"2018-12-16T14:00:43","date_gmt":"2018-12-16T14:00:43","guid":{"rendered":"http:\/\/writeasync.net\/?p=5599"},"modified":"2018-12-15T15:44:15","modified_gmt":"2018-12-15T15:44:15","slug":"building-an-adventure-game-part-2","status":"publish","type":"post","link":"http:\/\/writeasync.net\/?p=5599","title":{"rendered":"Building an adventure game: part 2"},"content":{"rendered":"

Previously, I recounted day 1 of my adventure game project<\/a>. Let’s continue.<\/p>\n

Day 2<\/h2>\n

This was a short day.<\/p>\n

First I observe that it isn’t really necessary for the caller of Game<\/code> to pass the MessageBus<\/code>, so I change that. Commit.<\/a> Then I determine that the “App” project is really better described as a “Sample” use case and change the names accordingly. Commit.<\/a><\/p>\n

Day 3<\/h2>\n

Every text adventure game needs to interpret user input so I get to work building the SentenceParser<\/code>. I start with a simple test<\/a> based around the existing InputMessage<\/code> protocol already established by the TextConsole<\/code>. I quickly decide that the output SentenceMessage<\/code> should split the input into a single verb and noun<\/a>. Since the parser subscribes to input messages on construction, I make sure it is a good citizen by implementing the Dispose pattern to unsubscribe<\/a>. Finally, I incorporate the code I have so far<\/a> into the sample Game<\/code>.<\/p>\n

Day 4<\/h2>\n

So far the Game<\/code> can accept a very small set of commands. Unfortunately, “quit” isn’t one of them, so there is no way to exit. I change this by first accepting a CancellationToken<\/code> in TextConsole<\/code><\/a>. Then I make it actually respond to cancellation requests<\/a>. After a bit of refactoring<\/a>, I add some Game<\/code> code to handle unknown verbs<\/a>. As a last step, I add the “quit” command<\/a>, thus completing the day’s work.<\/p>\n

Day 5<\/h2>\n

Today is all about Words<\/code>. So far the game only knows how to handle exact matches for verbs and ignores nouns. Let’s start implementing the concept of a synonym using a Word<\/code> class<\/a> to track the “actual” word entered by the user as well as the “primary” word that we match it against. The next test shows this in action<\/a> by accepting “see,” “inspect,” or “examine” as synonyms for the primary verb “look.” Several test and implementation cycles later, I am ready to incorporate a few words into the game<\/a> — “greet” (“hello,” “hi”) and “quit” (“exit”). Since I’m on a roll, I add “take” (“get”) to the game<\/a> as well. I end the day by extracting the primary words into a Verb class<\/a> that I later promote to the top level<\/a>.<\/p>\n

Day 6<\/h2>\n

An adventure game with no rooms to explore is hardly a game at all. Thus I begin building an abstract Room<\/code> class with methods to Enter and Register verbs<\/a>. My plan with this is to activate the behavior of the room (i.e. allow it to respond to commands, etc.) in Enter()<\/code> and unregister\/unsubscribe everything in Leave()<\/code> which I implement next<\/a>. Note that I am explicitly not using the Dispose pattern here because Dispose implies destruction; rather, I want rooms to live on even after the player has left since reentry is always possible, hence the Enter\/Leave semantics. With enough of the behavior fleshed out, I add a single MainRoom<\/code> to the sample game<\/a> where I move all the verb handling logic so far.<\/p>\n

Day 7<\/h2>\n

Looking at the code today, I don’t like how the TextConsole<\/code> does double duty as a console processor and an input loop. I begin to extract the loop behavior<\/a> into InputLoop<\/code>. To avoid major rework of the code I add an intermediary NewLoop()<\/code> factory method<\/a> to TextConsole<\/code>.<\/p>\n

Next, I look at MainRoom<\/code> and decide that it doesn’t make a lot of sense for a specific room instance to handle a global message like “quit.” As I start to extract this behavior, I realize that there is a flaw. My initial approach involves subscribing to the SentenceMessage<\/code> in the Game’s Run()<\/code> method to respond directly to the “quit” verb. Unfortunately, MainRoom<\/code> is also subscribed so I end up with two responses — the real quit behavior, followed by the unknown verb behavior of Room (“I don’t know what ‘quit’ means”). I don’t commit anything because the code doesn’t yet work.<\/p>\n

Day 8<\/h2>\n

I am determined to solve the previous day’s problem and I have a plan. Instead of only allowing void<\/code> (Action<\/code>) methods for MessageBus<\/code> subscribers, I add support for bool<\/code> return values<\/a>. In the spirit of not breaking things, this support does not replace the existing code but rather allows a second type of subscriber. Eventually I make it so that returning ‘true’ stops subsequent subscribers from processing<\/a>. Now I can actually implement the “quit” feature<\/a> from yesterday by having the quit handler return true<\/code> if it detects the “quit” verb and false<\/code> otherwise, allowing the room to process everything else. Finally, I extract this pattern into QuitHandler<\/code><\/a> and use it in the Game<\/a>.<\/p>\n

At this point I have a game with a single room that understands a few commands and allows you to quit. It’s not much but it’s something!<\/p>\n","protected":false},"excerpt":{"rendered":"

Previously, I recounted day 1 of my adventure game project. Let’s continue. Day 2 This was a short day. First I observe that it isn’t really necessary for the caller of Game to pass the MessageBus, so I change that.… <\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[91,41],"tags":[],"class_list":["post-5599","post","type-post","status-publish","format-standard","hentry","category-design","category-tdd"],"_links":{"self":[{"href":"http:\/\/writeasync.net\/index.php?rest_route=\/wp\/v2\/posts\/5599","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/writeasync.net\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/writeasync.net\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/writeasync.net\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/writeasync.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=5599"}],"version-history":[{"count":3,"href":"http:\/\/writeasync.net\/index.php?rest_route=\/wp\/v2\/posts\/5599\/revisions"}],"predecessor-version":[{"id":5602,"href":"http:\/\/writeasync.net\/index.php?rest_route=\/wp\/v2\/posts\/5599\/revisions\/5602"}],"wp:attachment":[{"href":"http:\/\/writeasync.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=5599"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/writeasync.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=5599"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/writeasync.net\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=5599"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}