Day: December 27, 2018

Calling Apex Methods In Lightning web components

Let’s discuss here how to call the apex class from the Lightning web components. Lightning web components can import methods from Apex classes into the JavaScript classes using ES6 import. Once after importing the apex class method you can able call the apex methods as functions into the component by calling either via the wire service or imperatively. Before you use an Apex method, make sure that there isn’t an easier way to get the data. See whether a base Lightning component, like lightning-record-form, lightning-record-view-form, or lightning-record-edit-form works for your use case. If they don’t give you enough flexibility, use a wire adapter like getListUi or getRecordUi. 

Refer this link for how to configure the Salesforce dx for web components 

Import Syntax 

You can able use default export syntax to import an Apex method via the @salesforce/apex scoped module into JavaScript controller class. The Syntax looks like below.

apexMethod—The imported symbol that identifies the Apex method.
Namespace—The namespace of the Salesforce organization. Specify a namespace unless the organization uses the default namespace (c), in which case don’t specify it.
Classname—The name of the Apex class.

Create Apex Class 

In this example, we will be getting account data and show it into the UI. Create an apex class using SFDX create apex class command.

Here is the apex class. To expose an Apex method to a Lightning web component, the method must be static and either global or public. Annotate the method with @AuraEnabled

Now you can able to call the apex class in  Lightning web component using these different ways.

  • Wire a property
  • Wire a function
  • Call a method imperatively

Wire an Apex Method to a Property

If an Apex method is annotated with @AuraEnabled(Cacheable=true), you can invoke it from a component via the wire service. You can @wire a property or a function. Here is the syntax

Create a Lightning web component using below SFDX commands

Here is the LWCWireEx.html markup for the lightning web components.

Here is the LWCWireEx.js class

Here is the LWCWireEx.js-meta.xml markup.

Push the changes to scratch org and add the lightning web component to the record page. You can able to see the result like below.

Wire an Apex Method to a Function

Now let’s look at how to wire an apex method to function.we will be updating the same code here to operate the apex method as function.

Update the LWCWireEx.js class as shown below

update the LWCWireEx.html markup as shown below

Push the changes to scratch org and add the lightning web component to the record page. You can able to see the result like below.

 

Call an Apex Method Imperatively

Now let’s see here how to call apex method imperatively. Create a new Lightning web component using the below SFDX command

Use the below ImperativEx.html code

Use the below ImperativEx.js class code

Use the below ImperativEx.js-meta.xml class code

push the changes to scratch org and add the lightning web component to the record page and you can able to see the below result when you click on the button .

Lightning web components Wire Service

Let’s discuss here how to use the wire service to get the Salesforce data from the server to lightning web components. You can use the Lightning data service or apex class to get the data from server and wire service is also one of the ways. To read Salesforce data, Lightning web components use a reactive wire service, which is built on Lightning Data Service. Components use @wire in their JavaScript class to read data from one of the wire adapters in the lightning/ui*Api namespace. The wire service provisions an immutable stream of data to the component. Each value in the stream is a newer version of the value that precedes it. when we call the wire service reactive in part because it supports reactive variables, which are prefixed with $. If a reactive variable changes, the wire service provisions new data. We say “provisions” instead of “requests” or “fetches” because if the data exists in the client cache, a network request may not be involved.

The wire service delegates control flow to the Lightning Web Components engine. Delegating control is great for reading operations, but it isn’t great for creating, update, and delete operations. As a developer, you want complete control over operations that change data. That’s why you perform create, update, and delete operations with a JavaScript API instead of with the wire service.

Wire Service Syntax

Import a wire adapter using named export syntax. Decorate a property or function with @wire and specify the wire adapter. Each wire adapter defines a data type.

adapterId (Identifier)—The identifier of the wire adapter.
adapterModule (String)—The identifier of the module that contains the wire adapter function, in the format namespace/moduleName. Take another look at the format! To import a module in JavaScript, use lightning/ui*Api instead of lightning-ui-*-api.
adapterConfig (Object)A configuration object specific to the wire adapter. Configuration object property values can be either strings or references to objects and fields imported from @salesforce/schema. Properties in the adapter config object can’t be undefined. If a property is undefined, the wire service doesn’t provision data.
propertyOrFunction—A private property or function that receives the stream of data from the wire service. If a property is decorated with @wire, the results are returned to the property’s data property or error property. If a function is decorated with @wire, the results are returned in an object with a data property and an error property. Now your code is like below if you convert the wire syntax.

import wire namespace into the JavaScript controller as shown below.

import getRecord from the lightning/uiRecordApi from lightning/ui*Api Wire Adapters and Functions.

Now call the @wire function to get the record data.

Create Lightning web components

create a lightning component in scratch org using the below sfdx command.

Here is the LWCWireExample.html code.

Here is the LWCWireExample.js code.

Here is the LWCWireExample.js-meta.xml markup code.

Push Source to the Scratch Org

Now push the changes to the scratch org by using this SFDX command.

Open Scratch Org by using this SFDX command.

Add this component to the record page and you can able to see the contact data as shown below.