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A Collection holds a set of Information we need to remember at a later point in time. It is designed for arrays of data objects following the same pattern. Each of these objects must have a unique primaryKey to be correctly identified later. We instantiate a Collection with help of an existing Agile Instance often called App. By doing so, the Collection is automatically bound to the Agile Instance it was created from.

const MY_COLLECTION = App.createCollection();

After we have successfully instantiated our Collection, we can start working with it.

MY_COLLECTION.collect({id: 1, name: "jeff"}); // Add Item to Collection
MY_COLLECTION.remove(1).everywhere(); // Remove Item from Collection
MY_COLLECTION.persist(); // Persists Collection Value into a Storage

If you want to find out more about the Collection's specific methods, check out the Methods docs. Most methods we use to modify, mutate and access the Collection are chainable.

MY_COLLECTION.collect({id: 1, name: "jeff"}).persist().removeGroup('myGroup').reset();

๐Ÿ”จ Usage#

For instance a Collection can be used to remember a flexible array of Todo objects.

const TODOS = App.createCollection();
TODOS.collect({id: 1, todo: "Clean bathroom"}, ["user1"]);
TODOS.collect({id: 2, todo: "Write Agile docs"}, ["user1"]);
// <- cleand bathroom

In the example above, we create a simple TODO Collection. After the instantiation, we add two todos to it and specify that both todos remain to the user1 Group. We do that to keep track of which todo relates to which user. Now that we cleaned our bathroom, we remove the todo related to the id 1 from the Collection and all Groups (everywhere).

โ›ณ๏ธ Sandbox#

Test the Collection yourself. It's only one click away. Just select your preferred Framework below.

  • React
  • Vue (coming soon)
  • Angular (coming soon)

๐Ÿ”น Item#

Each Data Object we add to our Collection (for example, with the collect() method) automatically becomes an Item and gets stored in a so-called data object directly in the Collection.

99: Item() // has value '{id: 99, name: "frank"}'
1: Item() // has value '{id: 1, name: "jeff"}'
2: Item() // has value '{id: 2, name: "hans"}'

It is best not to touch the data object at all and use the provided functions by the Collection to mutate and get access to it instead. For instance, there are many ways to access our collected Items.

  • getItem()#

    Returns a Item at a specific primary Key

    MY_COLLECTION.getItem(/* primary Key */); // Returns Item at the primary Key
  • getAllItems()#

    Returns all Items

    MY_COLLECTION.getAllItems(); // Returns '[Item(99), Item(1), Item(2)]'
  • getAllItemValues()#

    Returns the values of all Items

    MY_COLLECTION.getAllItemValues(); // Returns (see below)
    /* [
    {id: 99, name: "frank"},
    {id: 1, name: "jeff"},
    {id: 2, name: "hans"}

The most remarkable thing about Items is that they are an extension of the State Class, which means they provide the same powerful features.

MY_COLLECTION.collect({id: 1, name: "jeff"}); // Collect Data
const myItem = MY_COLLECTION.getItem(1); // Returns Item at primaryKey '1'
myItem.value; // Returns '{id: 1, name: "jeff"}'
myItem.patch({name: "frank"}); // Update property 'name' in Item
myItem.undo(); // Undo latest change

๐Ÿ‘จโ€๐Ÿ‘งโ€๐Ÿ‘ฆ Group#

Often applications need to categorize and preserve the ordering of structured data. In AgileTs, Groups are the cleanest way to do so. They allow us to cluster together data from a Collection as an array of primary Keys.

const MY_GROUP = MY_COLLECTION.createGroup("groupName", [/* initial Items */]);

A Group is an extension of the State Class and offers the same powerful features.

MY_STATE.undo(); // Undo latest change
MY_GROUP.reset(); // Reset Group to its intial Value
MY_STATE.persist(); // Persist Group Value into Storage

We access the Group output with help of the output property, since the value property is used to hold the primaryKeys.

MY_GROUP.value; // Returns [1, 20, 5]
MY_GROUP.output; // Returns (see below)
/* [
{id: 1, name: "frank"},
{id: 20, name: "jeff"},
{id: 5, name: "hans"}

For instance, we can use a Group to cluster a Post Collection into User Posts of the logged-in user.


In the above code snippet, we have two Collections, one for users and another for posts. We can collect posts specific to a user and group them automatically by the user's id.

๐Ÿ”ฎ Selector#

Sometimes we need access to one specific Item of a Collection in the long term. Therefore, AgileTs offers the Selector.

const MY_SELECTOR = MY_COLLECTION.createSelector("Selector name", /* to select primary Key */);

A Selector is an extension of the State Class, which represents one specific Item of the Collection until the Item gets deleted, or we select another one.

const mySelector =; // Returns extension of the Item at primaryKey '1'
mySelector.patch({name: "frank"}); // Update property 'name' in Item

For instance, a Selector finds its use to select the currently logged-in user from a User Collection.* current logged-in userId */);

๐Ÿ“ญ Props#



A Collection takes an optional configuration object as its only property. There are two different ways of configuring a Collection. Both have their advantages.

  • 1. The plain object way, which is notorious for its ease of use. Because here, we configure everything in a specific object. For instance, this makes the creation of Groups pretty straightforward. But on the other hand, it gives us some limitations since we aren't creating and configuring the Groups and Selectors on our own. The Collection takes care of it instead.

    const Collection = App.createCollection({
    key: 'dummyCollection',
    group: ["dummyGroup"]
  • 2. The function way, where a function, which has the Collection as first parameter, returns the configuration object. This gives us more freedom in configuring Instances like Groups, since we have access to the Collection and can create them on our own.

    const Collection = App.createCollection((collection) => ({
    key: 'dummyCollection',
    group: {
    dummyGroup: collection.Group(["item1", "item2"])

Here is a Typescript Interface of the configuration object for quick reference, however each property will be explained in more detail below.

export interface CreateCollectionConfigInterface<DataType = DefaultItem> {
groups?: { [key: string]: Group<any> } | string[];
selectors?: { [key: string]: Selector<any> } | string[];
key?: CollectionKey;
primaryKey?: string;
defaultGroupKey?: GroupKey;
initialData?: Array<DataType>;


The initial Groups of our Collection are defined with this property's help. There are two ways of doing this. The first one is to pass an Array of Group Names. AgileTs will than take care of the Group's creation and calls them after the previously passed names.

const MY_COLLECTION = App.createCollection({
groups: ["myGroup1", "myGroup2"]

The way mentioned above has some limitations. For instance, we can't define any initial Items. Luckily there is a second way, where we have access to the Collection itself.

const MY_COLLECTION = App.createCollection((collection) => ({
key: 'dummyCollection',
group: {
myGroup1: collection.Group(["item1", "item2"]),
myGroup2: collection.Group(["item5", "item2", "item6"])

With the help of the Collection, we can 'instantiate' the Groups on our own, which gives us much more freedom configuring in configuring them.


The initial Selectors of our Collection are defined with this property's help. As with the groups property, there are two ways of doing that. The first one is to pass an Array of Selector Names. AgileTs will than take care of the Selector's creation and calls them after the previously passed names.

const MY_COLLECTION = App.createCollection({
selectors: ["mySelector1", "mySelector2"]

The way mentioned above has some limitations. For instance, we can't define the initial selected Item Key. Luckily there is a second way, where we have access to the Collection which gets created.

const MY_COLLECTION = App.createCollection((collection) => ({
key: 'dummyCollection',
selectors: {
mySelector1: collection.Selector("item1"),
mySelector2: collection.Selector("item3")

With the help of the Collection, we can 'instantiate' the Selectors on our own, which gives us much more freedom in configuring them.


The name/key is an optional property that is used to identify a specific Collection. Such key is pretty useful during debug sessions or if we persist our Collection, it automatically uses the Collection key as persist key. We recommend giving each Collection an unique key, since it has only advantages.

const MY_COLLECTION = App.createCollection({
key: "myKey"


It defines which property's value in collected data will be selected as primaryKey. By default, it is id. A primaryKey identifies a specific Item, and has to be part of each collected data.

const MY_COLLECTION = App.createCollection({
primaryKey: "key"
MY_COLLECTION.collect({key: 1, name: "hans"});
// ^
// |
// primary Key ----------


The defaultGroupKey describes the name/key of the default Group. The default Group represents all Items of the Collection. By default, its is default.

const MY_COLLECTION = App.createCollection({
defaultGroupKey: "allItemsOfCollection"


The initial Data of our Collection.

const MY_COLLECTION = App.createCollection({
initialData: [{id: 1, name: "hans"}, {id: 2, name: "frank"}]

๐ŸŸฆ Typescript#

A Collection is almost 100% typesafe and takes an optional generic type for type safety that has to be followed by each collected data object.

interface UserInterface {
id: number,
name: string
const MY_COLLECTION = App.createState<UserInterface>();
MY_COLLECTION.collect({id: "invalidType", animal: "Lion"}); // Error
MY_COLLECTION.collect({id: 1, name: "hans"}); // Success
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