Designing a Class of Food Ingredients in OOP

Question

I want to offer recipes to my users, so I get recipes from the source JSON(including their ingredients).

Currently, the ingredients can be extracted in three ways:

• 3 tomatoes (without a specific unit)
• 125ml of milk (volume unit, metric or imperial)
• 500g of pasta (unit of mass, metric or imperial)

Requirements

I want to use the DDD approach, so layered architecture.

I need to be able to display the ingredient as is, as suggested in my marker list above. The user can choose between metric or imperial representation.

• 3 tomatoes
• 125ml of milk or 1/2 cup of milk
• 55g of pasta or 2 ounces of pasta

My challenge

I'm not sure how to create a class in order to respect encapsulation and provide an easy-to-maintain design.

, Unit, Ingredient . . IngredientPresenter :

public String present(Ingredient ingredient) {
    if ( ingredient.isUnitless() ) 
        return ingredient.getQuantity() + " " + ingredient.getName();
    else
        return ingredient.getUnit() + " " + ingredient.getName();
}

, units, IngredientPresenter ( ).

, . , , , . , . IngredientPresenter :

public String present(Ingredient ingredient) {
    if ( ingredient instanceof UnitlessIngredient ) {
        UnitlessIngredient actualIngredient = (UnitlessIngredient) ingredient;
        return actualIngredient.getQuantity() + " " + actualIngredient.getName();
    } else {
        WithUnitIngredient actualIngredient = (WithUnitIngredient) ingredient;
        return actualIngredient.getUnit() + " " + actualIngredient.getName();
    }
}

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Answer 1

.

: present() , Ingredient.

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