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Typescript

OneTable provides TypeScript type declaration files so that OneTable APIs, requests and responses can be fully type checked.

Using the magic of TypeScript dynamic typing, OneTable automatically converts your OneTable schema into fully typed generic Model APIs. This way, OneTable creates type declarations for your table entities and attributes so that TypeScript will catch any invalid entity or entity attribute references.

For example:

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import {Entity, Model, Table} from 'dynamodb-onetable'

const MySchema = {
    ...
    models: {
        Account: {
            pk:    { type: String, value: 'account#${name}' },
            name:  { type: String },
        }
    } as const     // Required for TypeScript
}

When defining your OneTable schema for Typescript, you must use type objects (String, Date, Number etc) as the value for your type properties. When using Javascript, you can also use string values ('string', 'date', 'number'), but for Typescript, this will prevent the Typescript dynamic typing from working.

You also need to append the as const to the end of your "models" in the schema.

Typed Application Models

Using the Entity generic type, you can create types for your schema models.

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type Account = Entity<typeof MySchema.models.Account>

With these types, you can declare typed variables.

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let account: Account = {
    name: 'Coyote',        //  OK
    unknown: 42,           //  Error
}

Similarly you can use a typed version of getModel to retrieve a typed Model to interact with OneTable.

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//  Get an Account access model
let AccountModel: Model<Account> = table.getModel<Account>('Account')

let account = await AccountModel.create({
    name: 'Acme',               //  OK
    unknown: 42,                //  Error
})

account.name = 'Coyote'         //  OK
account.unknown = 42            //  Error

Type Enforcement

Attributes that are defined in the schema with the "required" property will be mandatory in your Entity types. Those without the "required" property will be optional.

The Model.create() API can take a subset of the defined properties, provided that all required properties are present. TypeScript will enforce this.

The Model.update() API can take a subset of the defined properties. Required properties are not required for update unless they are part of the PK/SK value templates.

The Model.find() and Model.remove() API can take a subset of defined properties.