---
title: Identity
---

The MVVM implementation of identity is built on top of what you find the [core](/arc/frontend/core/identity/).
To access identity in an MVVM solution with a view model, the `IdentityProvider` is hooked up to the [container](/arc/frontend/react/mvvm/tsyringe/)
through its interface `IIdentityProvider`.

> Note: This depends on the [MVVM Context](/arc/frontend/react/mvvm/mvvm-context/) being used.

```typescript
import { injectable } from 'tsyringe';
import { IIdentityProvider } from '@cratis/arc/identity';

type IdentityDetails = {
    department: string,
    age: number
};

@injectable()
export class MyViewModel {
    constructor(private readonly _identityProvider: IIdentityProvider) {
    }

    async sayHello() {
        const identity = await this._identityProvider.getCurrent<IdentityDetails>();
        console.log(`Hello '${identity.name}' from ´${identity.details.department}`);
    }
}
```

The code takes a dependency to the abstract class called `IIdentityProvider` representing the interface for the identity provider.
With this the code simply calls the `getCurrent()` method to get the identity.

:::note
The `<IdentityDetails>` above is a **type parameter** - it only shapes what TypeScript expects `identity.details` to look like at compile time and has no effect at runtime. `identity.details` is still the raw JSON object the identity provider returned.

If your details contain complex types like `Guid` that need to be properly instantiated - not left as plain JSON - pass a class **constructor** as a runtime argument to `getCurrent()` instead of (or in addition to) a type parameter, with an `@field` decorator on every property you want deserialized:

```typescript
import { injectable } from 'tsyringe';
import { IIdentityProvider } from '@cratis/arc/identity';
import { Guid, field } from '@cratis/fundamentals';

class IdentityDetails {
    @field(Guid)
    userId!: Guid;
}

@injectable()
export class MyViewModel {
    constructor(private readonly _identityProvider: IIdentityProvider) {
    }

    async sayHello() {
        // The constructor argument is what deserializes - not just a <IdentityDetails> type parameter.
        const identity = await this._identityProvider.getCurrent(IdentityDetails);
        console.log(identity.details.userId.toString());
    }
}
```

A class with no `@field` decorators cannot be deserialized into - the raw payload is passed through unchanged instead of being silently blanked.
:::