Having trouble getting value from server in lightning component

Question

component

<aura:component controller="AudioController">
    <aura:attribute name="setMeOnInit" type="String" default="default value" />
    <aura:handler name="init" value="{!this}" action="{!c.getRecURL}"/>
    <h1>{!v.setMeOnInit}</h1>
</aura:component>

Server controller

public class AudioController {

 @AuraEnabled
    public static String getRecURLdata() {
        Contract c = [SELECT Id, recURL__c FROM Contract WHERE Id = :ApexPages.currentPage().getParameters().get('id')];
        return 'hello from cont';
    }

}

Client controller

({
    "getRecURL" : function(cmp) {
        var action = cmp.get("c.getRecURLdata");

            action.setCallback(this, function(response) {
                cmp.set("v.setMeOnInit", response.getReturnValue());
            });

        $A.enqueueAction(action);
    }
})

These are mostly just test values. I'm trying to get "hello from cont" to show up in the component

Answer 1

Your code was failing because ApexPages can only be used from Visualforce page context.

If you actually need Id from SObject in your controller, then what I would suggest is to use is to use force:hasRecordId. More on this interface you can read here. Then your code would look like this. component.cmp:

<aura:component controller="AudioController" implements="force:hasRecordId">
    <aura:attribute name="setMeOnInit" type="String" default="default value" />
    <aura:handler name="init" value="{!this}" action="{!c.getRecURL}"/>
    <h1>{!v.setMeOnInit}</h1>
</aura:component>

AudioController.cls:

public class AudioController {

    @AuraEnabled
    public static String getRecURLdata(final Id recordId) {
        if (recordId.getSObjectType() == null) {
            throw new AuraHandledException('RecordId is null');
        }
        if (recordId.getSObjectType() != Contract.getSObjectType()) {
            throw new AuraHandledException('Wrong SObject Type. Please use this component on Contract record page');
        }
        Contract c = [SELECT Id, Name FROM Contract WHERE Id = :recordId];
        return 'hello from cont';
    }

}

componentController.js:

({
    "getRecURL" : function(component) {
        var action = component.get("c.getRecURLdata");
        action.setParams({
            recordId: component.get('v.recordId')
        })

        console.log('Hello World');
        action.setCallback(this, $A.getCallback(function(response) {
            let state = response.getState();
            if (state === 'SUCCESS') {
                component.set("v.setMeOnInit", response.getReturnValue());
            } else {
                console.error(response.getError()[0].message);
            }
        }));

        $A.enqueueAction(action);
    }
})

And you will need to write tests for AudioController and can pass recordId directly as a parameter. And won't need to manage Page parameters in your tests, which will lead to easier to read and maintain code.