How to create related record upon saving new custom object record?

Question

I'm making a Visualforce page where a new Customer__c record is created. Customer__c has a lookup field (recordContact__r) which refers to another custom object: Contact__c.

While the main object record is created fine, the related object record isn't created with this code. What am I missing?

Visualforce

<apex:page showHeader="false" standardController="Customer__c" extensions="ExtendCustomers" sidebar="false" standardstylesheets="false">
    <apex:form >

        <div>
                <apex:commandButton action="{!saveRecord}" value="Save"/>
        </div>
        <div>
                <apex:inputField value="{!Customer__c.Name}" />
                <apex:inputField value="{!Customer__c.recordContact__r.Name}" />
                <apex:inputField value="{!Customer__c.recordContact__r.Address__c}" />
                <apex:inputField value="{!Customer__c.recordContact__r.City__c}" />
                <apex:inputField value="{!Customer__c.recordContact__r.State__c}" />
                <apex:inputField value="{!Customer__c.recordContact__r.Zip__c} " /> 
                <apex:inputField value="{!Customer__c.Email__c}" />
                <apex:inputField value="{!Customer__c.Phone__c}" />
        </div>
    </apex:form>
</apex:page>

Extension

public with sharing class ExtendCustomers{
    public Customer__c newCustomer = new Customer__c();

    public ExtendCustomers(ApexPages.StandardController controller) {
        this.newCustomer = (Customer__c)controller.getRecord();
    }

    public PageReference saveRecord() {
        insert newCustomer;
    }
 }

Answer 1

Any DML operations only operate on the primary object, any modifications to parent objects are ignored (with some exceptions for specifying a parent relationship with a foreign id). You'll need to insert the Contact__c separately.

public void saveRecord() {
  upsert newCustomer.recordContact__r;
  upsert newCustomer;
}