Difference between revisions of "Cross Script Variables"
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*The variable names listed in the script can be named whatever you like - preferably something meaningful to their purpose. | *The variable names listed in the script can be named whatever you like - preferably something meaningful to their purpose. | ||
*You must declare a variable in the quest script BEFORE you can reference them in the read/write scripts described below. If you attempt to code your read/write commands and the variable has not yet been declared in the quest script you will receive a compiling error in your read/write script. | |||
Revision as of 13:42, 23 December 2010
This article is actually a discussion which was brought into the Main Wiki because it has interesting or important information. It should be converted into an actual article; if you can do this, it would be appreciated.
If you are looking for a way to get the value of a variable from one script running on one object to a script running on another object I imagine you may have entered the above article name or something similar to it in your search for an answer. As you first begin writing mods you will probably notice that Oblivion assumes the only variables that should be universally accessible are the Global variables. This would not be a terrible thing except that all Global variables are treated as floats. (See Floating Point.)
It is possible a time will come in writing a script when you will wish to have a repository to store variable values that can be read from and written to by any script. Fortunately this is possible. This article addresses a method for not only storing and retrieving non-float numeric values, but object references as well. This could prove very handy when creating dynamic game scenarios.
The Basics
A scenario for creating and testing this type of functionality includes at least three features:
1 - A quest script that acts as the database for storing values. (One might want to read over the article Quest scripts to get familiar with the source of this idea.)
2 - A script that writes a value to one of the variables in the "database" Quest script when it is activated.
3 - A script that reads a value from one of the variables in the "database" Quest script when it is activated.
Using this basic model you should be able to easily construct a simple scenario to see this functionality in action.
The Quest Script
The quest script acts as a database. Unfortunately Oblivion doesn't provide the powerful database features you would find in an SQL database service. Still, it does provide the quest script where the most basic database functionality can be achieved - a command syntax for reading and writing to its variables from external scripts.
The script:
Scriptname MyQuestScriptDatabase ref refVar ; reference values can be stored and retrieved float floatVar ; float values can be stored and retrieved short ShortVar ; integer values can be stored and retrieved begin GameMode ; you don't have to put anything in here ; in fact you probably shouldn't. nothing is required here. ; if you set the value of a variable here it will be locked in ; instead you will set the values of these variables from outside scripts end
Make sure you set the Script Type as "Quest" in the script editor window and then save your script.
The script is very simple. You just declare all the variables you need for storing values. Too bad there isn't a way to create variables dynamically as with an SQL database. Still, this functionality is much better than nothing at all!
Notes
- You should NOT assign starting values to your variables. If you need to do this, do it using some other method. Setting values within this script essentially locks the value in. There may be a workaround for doing this, but more testing will be required.
- The variable names listed in the script can be named whatever you like - preferably something meaningful to their purpose.
- You must declare a variable in the quest script BEFORE you can reference them in the read/write scripts described below. If you attempt to code your read/write commands and the variable has not yet been declared in the quest script you will receive a compiling error in your read/write script.
The next part of this step is to create a quest. You can read up on the steps for creating a quest on the wiki. Just keep in mind that the only setting needed for creating this functionality is the "Script" setting under the Quest Data tab. Once you create and name your quest select your quest script from above under the script setting for the quest. (For these examples the quest is named MyQuest.)
Notes
- You do not need to start the quest! The values within the quest can be written to and read from even if it is never started. And anyway it saves on CPU cycles.
Storing a Value
Okay! Now that you have your quest and a quest script associated with it you need to know how to write values to it.
The script:
Scriptname MyWritingScript ref refVar ; reference values can be stored and retrieved float floatVar ; float values can be stored and retrieved short ShortVar ; integer values can be stored and retrieved begin onActivate set "MyQuest".refVar to "ObjectReference" ; or some reference variable set "MyQuest".floatVar to 1234567890 ; or some float variable set "MyQuest".ShortVar to 2012 ; or some integer variable end
That's it! Now associate this script with some object that can be "activated". When the player or an actor activates the object the values listed above will be assigned to the script variables in the quest script.
It's very important to notice where quotes were used in the example script. These are required. If the quotes are not used the script will fail to work properly. Yes, the script will compile, but the values will not be written to the quest script. References as well as the reference for the quest require these quotation marks. However, in the case of a reference variable - quotes are only required when setting the value of the reference variable.
set "MyQuest".refVar to ThisReferenceVar
Reading a Value
Now that you know how to write values to your quest script database you just need to know how to read them.
The script :
Scriptname MyReadingScript ref refVar ; reference value as stored ref refVarRetrieved ; reference value as retrieved float floatVar ; float value as stored float floatVarRetrieved ; float value as retrieved short ShortVar ; integer value as stored short ShortVarRetrieved ; integer value as retrieved begin OnActivate set refVarRetrieved to "MyQuest".refVar set floatVarRetrieved to "MyQuest".floatVar set ShortVarRetrieved to "MyQuest".ShortVar MessageBoxEx "See my reference: %n See my float: %g See my integer: %.0f", refVarRetrieved, floatVarRetrieved, ShortVarRetrieved end
Again the quotes around the name of your quest are critical for this to work. Also, if you use this script exactly as written the message box will show the name of your reference rather than the reference. See MessageBoxEx for more. But the reference value is there and ready for use.
Practical Applications
So one might be wondering where functionality like this might prove useful. If you're just writing simple mods this type of functionality may seem a bit excessive. But take as an example a mod where the player will only belong to one faction (other than the player faction of course.) Oblivion is designed assuming the player might be a member of many factions. But what if your mod only allowed the player be a member of one faction? And what if the relationships between factions was absolutely critical to the playing out of the other scripts and behaviors in your mod? In this situation you might find yourself writing scripts where you would do a long series of repetitive checks like these:
if (player.GetInFaction FactionRef == 1)
These checks would go through each possible faction and could start to get a little hard on the eyes if there were a great many factions. This would make trouble shooting your scripts a bit more difficult too.
Using the functionality discussed in this article you could store the player's faction in a quest script and just retrieve it with a few lines of code each time a script needed the information! If the player's faction could switch you would just write code to change the value in the quest script for those situations.
Final Notes
- All the example scripts above are for proof-of-concept testing. They are simplistic for the sake of study. Application of these concepts would include additional content in each script.
- It is possible (and probably should be tested) that an object script could be used in place of a quest script (for the database feature).
- It is possible other variable types provided through the OBSE could be stored and retrieved using this system. For example, strings and arrays. Further testing of this is needed.
Additional Reading
The above articles should be read for reference purposes. Although not directly related it is valuable to note that these are only conditionals that appear to offer the functionality discussed in this article, but do not. Still, the syntax for reading and writing to a quest script was derived from notes found in these articles and so are worth reviewing.