I'm trying to make an IRecipe that determines the output item from NBT saved to the input item. I'd really like to know what I'm doing wrong and how to fix it.

 

public class Destack implements IRecipe {

private final ItemStack recipeOutput;
private final ItemStack recipeInput;

public Destack () {
	ItemStack outStack = new ItemStack(DenseCraft.stackOf);
	outStack.stackTagCompound = new NBTTagCompound();

	ItemStack inStack = new ItemStack(DenseCraft.stackOf);
	inStack.stackTagCompound = new NBTTagCompound();

	this.recipeInput = inStack;

	if (inStack.stackTagCompound
			.getInteger("iterations") > 1) {
		outStack.stackTagCompound.setInteger("iterations", inStack.stackTagCompound.getInteger("iterations")-1);
		outStack.stackTagCompound.setInteger("itemid", inStack.stackTagCompound.getInteger("itemid"));
		outStack.stackTagCompound.setString("itemtype", inStack.stackTagCompound.getString("itemtype"));
		this.recipeOutput = outStack;
	} else if (inStack.stackTagCompound.getInteger("iterations") == 1) {
		this.recipeOutput = new ItemStack(
				Item.getItemById(inStack.stackTagCompound.getInteger("itemid")),
				new ItemStack(Item.getItemById(inStack.stackTagCompound.getInteger("itemid"))).getMaxStackSize()
				);
	} else {
		this.recipeOutput = this.recipeInput;
	}
}

@Override
public boolean matches(InventoryCrafting crafting, World world) {

	int numberOfItemsInGrid = 0;
	for (int i = 0; i < 3; i++) {
		for (int j = 0; j < 3; j++) {
			ItemStack item = crafting.getStackInRowAndColumn(i, j);
			if (item != null) {
				numberOfItemsInGrid++;
			}
		}
	}
	if (numberOfItemsInGrid == 1) {
		for (int i = 0; i < 3; i++) {
			for (int j = 0; j < 3; j++) {
				ItemStack item = crafting.getStackInRowAndColumn(i, j);
				if (item != null) {
					return (item == this.recipeInput);
				}
			}
		}
	}

	return false;
}

@Override
public ItemStack getCraftingResult(InventoryCrafting crafting) {
	return this.recipeOutput.copy();
}

@Override
public int getRecipeSize() {
	return 1;
}

@Override
public ItemStack getRecipeOutput() {
	return this.recipeOutput;
}

}

I moved everything down to getRecipeOutput, but it's still not working. Any ideas?

 

public class Destack implements IRecipe {

public final ItemStack recipeInput;

public Destack () {

	ItemStack inStack = new ItemStack(DenseCraft.stackOf);
	inStack.stackTagCompound = new NBTTagCompound();
	this.recipeInput = inStack;

}

@Override
public boolean matches(InventoryCrafting crafting, World world) {

	int numberOfItemsInGrid = 0;
	for (int i = 0; i < 3; i++) {
		for (int j = 0; j < 3; j++) {
			ItemStack item = crafting.getStackInRowAndColumn(i, j);
			if (item != null) {
				numberOfItemsInGrid++;
			}
		}
	}
	if (numberOfItemsInGrid == 1) {
		for (int i = 0; i < 3; i++) {
			for (int j = 0; j < 3; j++) {
				ItemStack item = crafting.getStackInRowAndColumn(i, j);
				if (item != null) {
					return (item == recipeInput);
				}
			}
		}
	}

	return false;
}

@Override
public ItemStack getCraftingResult(InventoryCrafting crafting) {
	return getRecipeOutput().copy();
}

@Override
public int getRecipeSize() {
	return 1;
}

@Override
public ItemStack getRecipeOutput() {

	ItemStack inStack = this.recipeInput;

	ItemStack outStack = new ItemStack(DenseCraft.stackOf);
	outStack.stackTagCompound = new NBTTagCompound();

	if (inStack.stackTagCompound.getInteger("iterations") > 1) {
		outStack.stackTagCompound.setInteger("iterations", inStack.stackTagCompound.getInteger("iterations")-1);
		outStack.stackTagCompound.setInteger("itemid", inStack.stackTagCompound.getInteger("itemid"));
		return outStack;
	} else if (inStack.stackTagCompound.getInteger("iterations") == 1) {
		return new ItemStack(
				Item.getItemById(inStack.stackTagCompound.getInteger("itemid")),
				new ItemStack(Item.getItemById(inStack.stackTagCompound.getInteger("itemid"))).getMaxStackSize()
				);
	} else {
		return inStack;
	}

}

}

You need to determine the result of the recipe in getCraftingResult, where you actually have access to the stacks being used, not just a dummy one