Compound slot initialization

Purpose

To explain how to initialise the value of the slots of a compound component and its members.

Prerequisites

You know how to create compound components.

Introduction

Sometimes, it might be useful to initialise the value of a compound component slot or the slot of a member to assure some behaviour when the component is loaded. You can perform this initialisation in the manifest file associated to your component, using the inits property of a compound component definition. In the following sections, we will explore this process and present some related details.

Sample case

To clarify the initialization process, we will use the currency-viewer compound created in this tutorial.

Initialising slots

You can initialise the slots of a compound component or the slots of its members in the manifest definition using the inits property, which is an array of objects with the following structure:

Property	Requirement	Description
description	Optional	A short description of this initialisation, e.g. responsibility.
memberIdRef	Required only for members initialization	The memberId of the member that contains the slot. It is only necessary if the slot belongs to a member.
slot	Required	slotId of the slot to be initialised
value	Required	The value to init the slot with, it can be an object, an array, a string, a number or a boolean.

If a slot is connected to more than one slot, the initialization will be performed in the order in which the connections were defined in the connections property of the compound component.

Initialising compound slots

If you want to set the initial value of the slot of a component, you should provide the slotId of the desired slot. Remember that when initialising compounds, the memberIdRef property should not be defined.

Initialising member slots

Let's say that we want to have the following default values for our compound:

slot	memberIdRef	Init value
base	currencyConverter	GBP (Pound sterling)
foreignCurrency	currencyConverter	EUR
date	currencyConverter	2016-06-24

To aim that, we should extend the inits property of the compound definition as follows:

    // ...
    "compoundComponents": [
      {
        "artifactId": "currency-viewer",
        // ...
        "inits": [
          {
            "slot": "base",
            "memberIdRef": "currencyConverter",
            "value": "GBP",
            "description": "Pound sterling would be the default base currency"
          },
          {
            "slot": "foreignCurrency",
            "memberIdRef": "currencyConverter",
            "value": "EUR",
            "description": "Euro would be the default target currency"
          },
          {
            "slot": "base",
            "memberIdRef": "currencyConverter",
            "value": "2018-06-23",
            "description": "Default date for the currency conversion"
          }
        ]
      },
      // ...
    ],
    // ...

Note that if the component of a member has been initialised within its definition, that initialisation will be overwritten by the one you define within the compound that contains it as a member.

Result

If you run the demo page of the currency-viewer component, you will note that the input texts have the values that you defined as presented below:

Initialised members demo

You can also check the results at the online demo.