Summing Up

There's doubtless a great deal more that could be done to improve even this simple little game, but that can be left as an exercise for the interested reader. We have taken The Adventures of Heidi as far as we need to for the purposes of this tutorial, and in the next chapter we'll move on to pastures new.

In the course of this chapter we've encountered several new features of the TADS 3 language and the adv3Lite library. In particular:

The use of listenDesc, smellDesc, feelDesc and tasteDesc to provide responses to LISTEN, SMELL, FEEL and TASTE commands.
Attaching a string to the direction property of a Room instead of another Room, to display a message to the player instead of moving the player character.
Pointing a direction property to a TravelConnector object (in this case a StairwayUp) instead of another Room (or string).
Going beyond implementing everything as either a Room or a Thing to take advantage of the behaviour already defined on a special class (in this case StairwayUp).
The use of message properties such as cannotTakeMsg and cannotEnterMsg to customize the responses to actions that are disallowed.
The use of cannotGoThatWayMsg and of the cannotGoThatWay(dir) method to customize the response to an attempt to travel in a direction that's not allowed.
The use of the logical operators &&, || and !
The use of Doer objects as a means of interrupting the normal course of a command and making it do something different.
A quick foretaste of the dobjFor() mechanism for customizing action responses.
The use of the roomBeforeAction() method of Rooms to intercept actions performed there.
The use of exit and abort to stop an action in its tracks.
An introduction to the use of message parameter substitutions to make textual output more flexible and appropriate to its context.

This certainly isn't everything you need to know to become a master of adv3Lite, but we've come a long way. If you've mastered all the material we've covered so far, you now have all the basic skills you need to write Interactive Fiction with adv3Lite, and if you wanted to make a start on implementing your own masterpiece, you'd now be in a position to do so. At the very least you could start laying out your map, implementing some of the standard objects within it, and coding a few non-standard responses, although you'd need to resume this tutorial before you tried anything very advanced. On the other hand, if you'd rather just carry straight on with this tutorial, that would be good too.

It's said that a non-Jew once approached Rabbi Shammai and told the rabbi he would convert to Judaism if the rabbi managed to teach him the entire torah (the Jewish law) while he (the gentile) stood on one leg. Apparently Shammai drove him away with a measuring-rod. The gentile then approached Shammai's rival Rabbi Hillel with the same offer. Hillel replied "Whatever you would hate people to do to you, don't do to others; the rest is commentary, go and learn." A latter-day Rabbi Hillel asked a similar question about adv3Lite might have said, "It's all about defining objects, properties and methods; the rest is detail, go and learn." You've now learned the basics of defining objects; in the chapters that follow we'll continue to explore some of the detail.

Finally, here's the complete listing of The Adventures of Heidi as we've now left it:

#charset "us-ascii"

#include <tads.h>
#include "advlite.h"

versionInfo: GameID
    IFID = '' // obtain IFID from http://www.tads.org/ifidgen/ifidgen
    name = 'The Adventures of Heidi'
    byline = 'by A.N. Author'
    htmlByline = 'by <a href="mailto:an.author@somemail.com">
                  A.N. Author</a>'
    version = '1'
    authorEmail = 'A.N. Author <an.author@somemail.com>'
    desc = 'A simple game borrowed from the Inform Beginner\'s Guide by Roger
        Firth and Sonja Kesserich.'
    htmlDesc = 'A simple game borrowed from the <i>Inform Beginner\'s Guide</i>
        by Roger Firth and Sonja Kesserich.'    
    
;

gameMain: GameMainDef
    /* Define the initial player character; this is compulsory */
    initialPlayerChar = me
;


/* The starting location; this can be called anything you like */

beforeCottage: Room 'In front of a Cottage'
    "You stand outside a cottage. The forest stretches east. "
    
    east = forest
    in = 'It\'s such a lovely day -- much too nice to go inside. '
;

+ cottage: Thing 'tiny cottage;small simple; house home'
    "It's small and simple, but you're very happy here. "
    
    isFixed = true
    
    cannotEnterMsg = location.in
    cannotTakeMsg = 'You\'re not a tortoise; you can\'t carry your home with
        you. '
;

/* 
 *   The player character object. This doesn't have to be called me, but me is a
 *   convenient name. If you change it to something else, rememember to change
 *   gameMain.initialPlayerChar accordingly.
 */

+ me: Player 'you;;heidi'          
    bulkCapacity = 1
;


forest: Room 'Deep in the forest'
    "Through the dense foliage, you glimpse a building to the west. A track
    heads to the northeast. "
    
    west = beforeCottage
    northeast = clearing
;

+ bird: Thing 'baby bird;;nestling'
    "Too young to fly, the nestling tweets helplessly. "
       
    bulk = 1
    
    listenDesc = "The nestling sounds scared and in need of assistance. "
;


clearing: Room 'A forest clearing'
    "A tall sycamore stands in the middle of this clearing. The path winds
    southwest through the trees. "
    
    southwest = forest
    up = tree
;

+ nest: Thing 'bird\'s nest; carefully woven; moss twigs'
    "The nest is carefully woven of twigs and moss. "
    
    contType = In   
    bulk = 1
;


+ tree: StairwayUp 'tall sycamore tree;;stout proud'     
    "Standing proud in the middle of the clearing, the stout tree looks easy to
    climb."
    
    destination = topOfTree
    
    travelDesc = "You <<one of>> manage to scramble all the way up <<or>> once 
        again climb <<stopping>> to the top of the tree. "
;

topOfTree: Room 'At the top of the tree'
    "You cling precariously to the trunk. "
    
    down = clearing
    
    cannotGoThatWay(dir)
    {
        "The only way from here is down. ";
    }
    
    roomBeforeAction()
    {
        if(gActionIs(Drop))
        {
            gDobj.actionMoveInto(clearing);
            "{The subj dobj} {falls} to the ground below. ";
            exit;
        }
    }
;

+ branch: Thing 'wide firm bough; flat; branch'
    "It's flat enough to support a small object. "
    
    iFixed = true
    isListed = true
    contType = On
    
    afterAction()
    {
        if(nest.isIn(self) && bird.isIn(nest))
            finishGameMsg(ftVictory, [finishOptionUndo]);
    }
;

modify Room
    cannotGoThatWayMsg = 'Better stick to the path. '
;

Doer 'go dir'
    execAction(curCmd)
    {
        "You're not aboard a ship. ";
        abort;
    }
    
    direction = [portDir, starboardDir, foreDir, aftDir]
;