//只有子类可以调用，外界不能调用
//这里，Money这个领域依赖了ICurrencyLookup接口，保持领域对外界没有依赖
protected Money(decimal amount, string currencyCode, ICurrencyLookup currencyLookup)
{
if (string.IsNullOrEmpty(currencyCode))
{
throw new ArgumentNullException(nameof(currencyCode), "Currency code must be specified");
}
var currency = currencyLookup.FindCurrency(currencyCode);
if (!currency.InUse)
{
throw new ArgumentException($"Currency {currencyCode} is not valid");
}
if (decimal.Round(amount, currency.DecimalPlaces) != amount)
{
throw new ArgumentOutOfRangeException(nameof(amount), $"Amount in {currencyCode} cannot have more than {currency.DecimalPlaces} decimals");
}
Amount = amount;
Currency = currency;
}
protected Money(decimal amount, CurrencyDetails currency)
{
Amount = amount;
Currency = currency;
}
