Yaratımsal Kalıplar — Constructor Ne Zaman Yetmez

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public record CardControls(
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        Money dailyPurchaseLimit,
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        Money dailyAtmLimit,
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        Money contactlessLimit,     // per transaction, no PIN asked
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        boolean onlineEnabled,
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        boolean abroadEnabled) {
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    public CardControls {
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        Currency currency = dailyPurchaseLimit.currency();
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        if (!dailyAtmLimit.currency().equals(currency) || !contactlessLimit.currency().equals(currency)) {
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            throw new IllegalArgumentException("all limits must share one currency");
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        }
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        if (contactlessLimit.amount().compareTo(dailyPurchaseLimit.amount()) > 0) {
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            throw new IllegalArgumentException("contactless limit above daily purchase limit");
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        }
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    }
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    // A named starting point; the amounts come from the card product, not from here.
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    public static CardControls standardFor(CardProduct product) {
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        return new CardControls(product.purchaseLimit(), product.atmLimit(),
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                product.contactlessLimit(), true, false);
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    }
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    public static CardControlsBuilder builder(CardProduct product) {
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        return new CardControlsBuilder(standardFor(product));
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    }
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}

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public final class CardControlsBuilder {
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    private Money dailyPurchaseLimit;
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    private Money dailyAtmLimit;
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    private Money contactlessLimit;
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    private boolean onlineEnabled;
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    private boolean abroadEnabled;
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    // Starts from the product's defaults; the caller changes only what differs.
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    CardControlsBuilder(CardControls start) {
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        this.dailyPurchaseLimit = start.dailyPurchaseLimit();
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        this.dailyAtmLimit = start.dailyAtmLimit();
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        this.contactlessLimit = start.contactlessLimit();
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        this.onlineEnabled = start.onlineEnabled();
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        this.abroadEnabled = start.abroadEnabled();
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    }
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    public CardControlsBuilder dailyPurchaseLimit(Money value) { this.dailyPurchaseLimit = value; return this; }
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    public CardControlsBuilder dailyAtmLimit(Money value) { this.dailyAtmLimit = value; return this; }
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    public CardControlsBuilder contactlessLimit(Money value) { this.contactlessLimit = value; return this; }
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    public CardControlsBuilder onlineEnabled(boolean value) { this.onlineEnabled = value; return this; }
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    public CardControlsBuilder abroadEnabled(boolean value) { this.abroadEnabled = value; return this; }
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    // Same door as new: the record's compact constructor checks everything once.
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    public CardControls build() {
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        return new CardControls(dailyPurchaseLimit, dailyAtmLimit, contactlessLimit,
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                onlineEnabled, abroadEnabled);
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    }
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}

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@Service
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public class CardSettingsService {
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    private final CardRepository cards;
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    CardSettingsService(CardRepository cards) {
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        this.cards = cards;
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    }
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    @Transactional
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    public void limitToDomesticInStore(CardId cardId, Money atmLimit) {
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        Card card = cards.findById(cardId).orElseThrow();
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        CardControls controls = CardControls.builder(card.product())
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                .dailyAtmLimit(atmLimit)
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                .abroadEnabled(false)
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                .onlineEnabled(false)
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                .build();
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        card.apply(controls);
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    }
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}

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// The positional version: it compiles, and the call site does not say which Money is which.
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public class LegacyCardControls {
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    public LegacyCardControls(Money dailyPurchaseLimit, Money dailyAtmLimit, Money contactlessLimit,
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                              boolean onlineEnabled, boolean abroadEnabled) {
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        // ...
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    }
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}
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// Somewhere else: ATM and purchase limits swapped, two booleans nobody can read.
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// new LegacyCardControls(atmLimit, purchaseLimit, contactless, false, true);