There are two ways to alter the base game content:
- Replace one of the game files with your version. This is not recommended, and it can cause issues with other mods that want to change items in the file. This method should only be used when you must replace one of the XML or Lua files in the UI.
- Use SQLite or XML commands to manipulate the database values. This is the preferred and much simpler way to alter the game database, but you can't use it to change the UI.
To replace a game file, you need to make a file with the same name and contents in your project, then make your changes. Then, you need to add an Import Files action to your mod, and add the file to that action. This will have the mod overwrite the base game file of the same name.
To alter the game database with SQLite, first make a new SQL file in your mod, and name it whatever you want. We will be using the following command:
UPDATE Table SET Column1=A, Column2=N WHERE Column3=B;
Update Table defines the Table to be updated. All of the table names can be found in GameplaySchema.sql in Base\Assets\Gameplay\Data\Schema\, or you can look in the XML database files.
SET Column1=A, Column2=N defines the changes that will be made to the column values for the table. Multiple columns can be changed in one statement, separated by a comma.
If we put on a semi-colon and just stopped here, our command would change every column value in the table! For example, the command: UPDATE Buildings SET Cost=10000; would make all the game buildings have a base cost of 10,000 production.
WHERE Column3=B; defines which rows will be changed. Only the rows which have a value of B in the column 'Column3' will be changed. You can also extend the WHERE expression to change multiple types of rows at a time: WHERE (Column3=B or Column4=C);
Lets change the Ranger unit so that is has a base sight of 5 tiles, turn off its zone of control, and change is required technology to Computers. First, we need to find the table that we need to update. We can find it in Units.xml, where there is a table called Units. We can see that there is a row with the primary key 'UNIT_RANGER' and that the column names for the stuff we want to change is related to BaseSightRange="3", ZoneOfControl="true", and PrereqTech="TECH_RIFLING". Now, we are ready to make our SQLite command:
UPDATE Units SET BaseSightRange=5, ZoneOfControl=0, PrereqTech='TECH_COMPUTERS' WHERE UnitType='UNIT_RANGER';
Once we have saved our SQL file, we just need to add an UpdateDatabase action to our mod, then add our SQL file to that action. (It would be really useful to explain this in more detail. For example, would editing a unit be a front end action or In-game Action?)
Tips:
- String values in SQLite are defined with single quotes rather than double quotes.
- Boolean (true or false) values in SQLite are handled with integer 0 and 1.
- You can add comments (the file will ignore these) in SQLite by putting a double hyphen at the beginning of the line --