Mixed support - API

[sync-by-unito]

Introduction

For JavaScript developers, a mixed type is a natural concept due to JavaScript’s type system.

Schema

We can add a new type to the support by the object schema. The name mixed captures the concept "property of different kinds" well.

const Person = {
  name: "Person",
  properties: {
    stuff: { type: "mixed" }, 
    stuffList1: { type: "list", objectType: "mixed" },
    stuffList2: "mixed[]",
  }
};

Additional requirements for mixed properties:

• cannot be marked optional since null is always a permitted value.
• can be indexed
• cannot be a primary key

Creating objects with mixed

Creating an object with a properties of mixed type should be natural for a JavaScript developer:

realm.write(() => {
  realm.create("Person", {
    stuff: 42,
    stuffList1: [ 
      42, 
      "Everything"
    ]
  });
});

Only the following types are supported: int, bool, float, double, string, data, date, objectId, uuid, decimal128 and links. Realm.create() will validate input accordingly.

Accessors

Due to the flexibility of JavaScript’s type system, we can return properties without much hassle.

var person;
realm.write(() => {
  person = realm.create("Person", {
    stuff: 42,
    stuffList1: [ 
      42, 
      "Everything" 
    ]
  });
});

person.stuffList1.forEach(item => {
  console.log(typeof(item));
  // outputs two lines: 'number', 'string'
});

Moreover, updating a property is supported:

var person;
realm.write(() => {
  person = realm.create("Person", {
    stuff: 42,
    stuffList1: [ 
      42, 
      "Everything" 
    ]
  });
});

realm.write(() => {
  person.stuff = "42";
});

Serialization

It is important to support JSON serialization.

var person;
realm.write(() => {
  person = realm.create("Person", {
    stuff: 42,
    stuffList1: [ 
      42, 
      "Everything"
    ]
  });
});

console.log(JSON.stringify(person));
// { stuff: 42, stuffList1: [ 42, "Everything" ] }

[kraenhansen]

When reading the scope, it seems to me that it won't be possible to store anything else than primitives in a property of Mixed type:

It should be possible to define a property of a class to be of Mixed type. This means that the property can hold values of all the primitive types (Int, Bool, Float, Double, String, Binary, Timestamp, ObjectId, UUID, Decimal128 and links). Lst must be supported too.

I suggest updating the description above to exclude the { name: "Arthur", harmless: "mostly" } example.

[kneth]

@kraenhansen I have removed it. According to the scope, links are supported, and we need to find a way to capture it. Using { name: "Arthur", harmless: "mostly" } was a clumsy example.