Adding meta timestamps

In this example we can easily create both updatedAt and createdAt attributes on our model. createdAt will use ElectroDB’s set and readOnly attribute properties, while updatedAt will make use of readOnly, and watch with the “watchAll” syntax: {watch: "*"}. By supplying an asterisk, instead of an array of attribute names, attributes can be defined to watch all changes to all attributes.

Using watch in conjunction with readOnly is another powerful modeling technique. This combination allows you to model attributes that can only be modified via the model and not via the user. This is useful for attributes that need to be locked down and/or strictly calculated.

Notable about this example is that both updatedAt and createdAt use the set property without using its arguments. The readOnly only prevents modification of an attributes on update, and patch. By disregarding the arguments passed to set, the updatedAt and createdAt attributes are then effectively locked down from user influence/manipulation.

{
  model: {
    entity: "transaction",
    service: "bank",
    version: "1"
  },
  attributes: {
    accountNumber: {
      type: "string"
    },
    transactionId: {
      type: "string"
    },
    description: {
      type: "string",
    },
    createdAt: {
      type: "number",
      readOnly: true,
      set: () => Date.now()
    },
    updatedAt: {
      type: "number",
      readOnly: true,
      watch: "*",
      set: () => Date.now()
    }
  },
  indexes: {
    transactions: {
      pk: {
        field: "pk",
        facets: ["accountNumber"]
      },
      sk: {
        field: "sk",
        facets: ["transactionId"]
      }
    }
  }
}