Synchronous Computed

About

Synchronous computed properties are directly declared in the state. Essentially, they are regular functions that automatically trigger recalculation when data in the State changes, assigning the computed result to the corresponding property in the State.

Creation Methods

Quick Creation

You can directly declare regular synchronous computation functions in the State.

import { createStore } from '@autostorejs/react';
const state = createStore({
  user:{
    firstName:"Zhang",
    lastName:"Fisher",
    fullName: (user)=>{
      return user.firstName+user.lastName
    } 
  }
})

• fullName is a synchronous computed property that depends on firstName and lastName. When either firstName or lastName changes, fullName will automatically recalculate.
• The first parameter (i.e., the scope) of fullName is specified by the scope parameter in createStore, which defaults to ObserverScopeRef.Current. Therefore, the first parameter of fullName is the user object.
• If the synchronous computation function is a regular function rather than an arrow function, the this context points to the computedObject created for the current computed property. See Computed Objects for details.
• Dependency collection for synchronous computed properties is automatic, requiring no manual specification.

Using computed

The standard way to create synchronous computed properties is using the computed(<getter>,<options>) function. By specifying options, you can have more flexible control over the behavior of computed properties.

const state = {
  user:{
    firstName:"Zhang",
    lastName:"Fisher",
    fullName:computed<string>((state)=>{
      return state.user.firstName+state.user.lastName
    },{ 
      scope:ObserverScopeRef.Root               // First parameter of the computation function
    }) 
  }
}

Since computedScope can be specified, the computation function can achieve relative computation.

• In the example above, calculating the subtotal of an order only requires {...,total:(book)=>book.price*book.count}, which looks very concise.

Configuration Parameters

When creating synchronous computed properties using computed(<getter>,<options>), you can specify the following parameters:

Parameter	Type	Default Value	Description
id	string		Unique identifier for the computed property, used to find the computed property object in computedObjects.
scope	ObserverScopeRef	ObserverScopeRef.Current	The first parameter of the computation function, i.e., the scope.
group	string		Used to group computed property objects, allowing execution of a group of computed properties using computedObjects.runGroup(name).
objectify	boolean	true	Whether to save the computed property object in store.computedObjects