How to store condition dependent item information in JSON

Question

I'm developing a RPG-game. After searching about various ways to save item information in RPG-game, I determined to save information in JSON files. The problem is that in my game, some equipment's stat depends on the character condition.

class Equipment {
    String name;
    double strength;
    double agility;
    
    Equipment(String name) {
        this.name = name;
    }

    checkCondition(Character character) {
        switch (this.name) {
            case "itemA" -> {
                strength = 20;
                      //This is what I mean by "condition dependent item"
                agility = character.strength > 30 ? 20 : 10;
            }

        
            case "itemB" -> strength = 40;
        }
    }
}

As you can see, "itemA"'s stat is dependent to characters' strength.

{
    "name": "itemB",
    "strength": 40,
    "agility": 0
}

This is how I planned to save the items, but "itemA" doesn't seem to fit in this form. Please let me know you have an idea to solve this problem.

Answer 1

I wouldn't do this based on item name. Instead, I'd implement a system of modifiers to describe what an item does, something like...

{
    name: "itemA",
    displayName: "Slippers of Mighty Grace",
    effects: [
        {
            type: "statCheck",
            stat: "strength",
            threshold: 31,
            effectsIfMet: [
                {
                    type: "statBoost",
                    stat: "agility",
                    value: 20
                }
            ],
            effectsIfNotMet: [
                {
                    type: "statBoost",
                    stat: "agility",
                    value: 10
                }
            ]
        }
    ]
}

When you load this item from JSON, you string together a matching pattern of polymorphic effect nodes, each with their own Apply method, something like this:

public class StatCheckEffect implements ItemEffect {
    public Stat stat;
    public int threshold;
    
    public ItemEffect[] effectsIfMet;
    public ItemEffect[] effectsIfNotMet;

    public void Apply(Character char) {
        if (char.GetStat(stat) >= threshold) {
            for(ItemEffect effect : effectsIfMet)
                effect.Apply(char);
        } else {
            for(ItemEffect effect : effectsIfNotMet)
                effect.Apply(char);
        }
    }
}

public class StatBoostEffect implements ItemEffect {
    public Stat stat;
    public int value;

    public void Apply(Character char) {
        char.ModifyStat(stat, value);
    }
}

When the item is equipped, you run the Apply() methods on all its top-level effects. When the character's status changes in a way that might affect equipment properties, you reset the character's stats to base and re-run the Apply() methods of all equipped gear to find the new net result. (More sophisticated caching to avoid redundant processing is possible, but do it the simple way first to check if you really need the added complexity)