New in version 10.5.0.
A Realm Set is a special object that allows you to store a collection of unique values. Realm Sets are based on JavaScript sets , but can only contain values of a single type and can only be modified within a write transaction. Sets allow you to perform math operations such as finding the union, intersection, or difference between two sets. To learn more about performing these operations, see the MDN docs for Implementing basic set operations.
To define a property type as a Realm Set, specify the data type you want in the set, followed by <>. For instance, for a set made of integer values, specify "int<>".
const characterSchema = { name: "Character", primaryKey: "_id", properties: { _id: "objectId", name: "string", levelsCompleted: "int<>", inventory: "string<>", },};To create an object with a Realm Set property, you must create the object within a write transaction. When defining your Realm object, initialize the Realm Set by passing an empty array or an array with your initial values.
let playerOne, playerTwo;realm.write(() => { playerOne = realm.create("Character", { _id: new BSON.ObjectId(), name: "PlayerOne", inventory: ["elixir", "compass", "glowing shield"], levelsCompleted: [4, 9], }); playerTwo = realm.create("Character", { _id: new BSON.ObjectId(), name: "PlayerTwo", inventory: ["estus flask", "gloves", "rune"], levelsCompleted: [1, 2, 5, 24], });});To add an item to a set, pass the new value to the <Realm.Set>.add() method within a write transaction.
realm.write(() => { playerOne.inventory.add("hammer"); playerOne.levelsCompleted.add(32);});To determine if a set contains a particular value, pass the value to the <Realm.Set>.has() method. The set.has() method will return true if the set contains the value specified.
const playerTwoHasCompletedLevelThree = playerTwo.levelsCompleted.has(3);console.log( `Is level three completed by playerTwo: ${playerTwoHasCompletedLevelThree}`);To discover how many items are in a set, you can check the set's size property.
const playerTwoInventorySize = playerTwo.inventory.size;console.log(`playerTwo has ${playerTwoInventorySize} inventory items`);To remove a specific value from a set, pass the value to the <Realm.Set>.delete() method within a write transaction.
realm.write(() => { playerOne.inventory.delete("compass");});To clear the set, run the <Realm.Set>.clear() method within a write transaction.
realm.write(() => { playerTwo.inventory.clear();});To traverse a set, use the <Realm.Set>.forEach() method or alternative iteration method.
playerOne.inventory.forEach((item) => { console.log(item);});The order of the Realm Set may be different from the order that the items were added.
You can track the set order by updating an array when a new value is added. For example:
function updateSetAndOrderedSetArray(set, orderedArray, value) { const oldSize = set.size; set.add(value); if (set.size > oldSize) { orderedArray.push(value); }}let playerOne;let levelsCompletedInOrder = [];const realm = await Realm.open({ path: "realm-files/data-type-realm", schema: [characterSchema],});realm.write(() => { playerOne = realm.create("Character", { _id: new BSON.ObjectId(), name: "PlayerOne", inventory: ["potion", "wand", "spell book"], levelsCompleted: [], });});realm.write(() => { updateSetAndOrderedSetArray( playerOne.levelsCompleted, levelsCompletedInOrder, 5 );});realm.write(() => { updateSetAndOrderedSetArray( playerOne.levelsCompleted, levelsCompletedInOrder, 12 );});realm.write(() => { updateSetAndOrderedSetArray( playerOne.levelsCompleted, levelsCompletedInOrder, 2 );});realm.write(() => { updateSetAndOrderedSetArray( playerOne.levelsCompleted, levelsCompletedInOrder, 7 );});console.log("set ordered", Array.from(playerOne.levelsCompleted)); console.log("insert ordered", levelsCompletedInOrder); realm.close();RetroSearch is an open source project built by @garambo | Open a GitHub Issue
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