在字段类型策略中获取父对象

Question

假设我有以下获取产品列表的查询。

query ProductList() {
  products() {
    name
    price
    stockQuantity
    isAvailable @client # This is a local-only field
  }
}

我还在内存缓存创建时为仅限本地字段添加了类型策略，并带有读取功能：

const cache = new InMemoryCache({
  typePolicies: { // Type policy map
    Product: {
      fields: { // Field policy map for the Product type
        isAvailable: { // Field policy for the isAvailable field
          read(existing, context) { // The read function for the isAvailable field
            // Return value
          }
        }
      }
    }
  }
});

如何在isAvailable读取函数中获取父Product对象的stockQuantity字段？

Answer 1

const cache = new InMemoryCache({
  typePolicies: { // Type policy map
    Product: {
      fields: { // Field policy map for the Product type
        isAvailable: { // Field policy for the isAvailable field
          read(existing, {readField}) { // The read function for the isAvailable field
            const stockQuantity = readField("stockQuantity");
            return stockQuantity ? true : false;
          }
        }
      }
    }
  }
});