How to validate the values before saving a record through lightning:recordEditForm and lightning:inputField?

Question

I'm using lightning:recordEditForm and lightning:inputField to update a record. I need to validate the values before updation and I couldn't find any ways to get the values from lightning:recordEditForm or lightning:inputField. How can I access the values from lightning:recordEditForm and lightning:inputField? Is it possible ? If not why was it not allowed ?

Component:

<aura:component >

    <aura:attribute name="fieldList" type="String[]" default="['Name','Email','Birthdate','Languages__c','MobilePhone']"/>

    <lightning:recordEditForm recordId="003XXXXXXXXXXXXXXX" objectApiName="Contact" onsubmit="{!c.submitData}">
        <lightning:messages />
        <aura:iteration items="{!v.fieldList}" var="field">
            <lightning:inputField aura:id="inputs" fieldName="{!field}" />
        </aura:iteration>
        <lightning:button class="slds-m-top_small" variant="brand" type="submit" name="update" label="Update" />
    </lightning:recordEditForm>

</aura:component>

Controller:

({
    submitData : function(component, event, helper) {
        var values = component.find('inputs');
        console.log('values',values);
        //Can't get the values.
    }
})

Answer 1

There is a way to bind the lighthning:inputField value to an Instance of an Object. Here is an Example code,

Parent Component:

<aura:component >

    <aura:attribute name="testContact" type="Contact" access="PUBLIC" default="{'sObjectType':'Contact'}"/>

    <div class="slds-box">
        <lightning:recordEditForm aura:id="recordEdit" objectApiName="Contact">
            <aura:iteration items="['LastName','Phone']" var="item">
                <c:inputFieldCmp aura:id="child" testContact="{!v.testContact}" fieldName="{!item}"/>
            </aura:iteration>
        </lightning:recordEditForm>
    </div> 

    <div  class="slds-m-around_medium">
        <lightning:button label="Save" variant="brand" onclick="{!c.recordSave}"/>
    </div>
</aura:component>

Child Component:

<aura:component >
    <aura:attribute name="testContact" type="Contact"/>
    <aura:attribute name="fieldName" type="String"/>

    <lightning:inputField aura:id='inputField' fieldName="{!v.fieldName}" onchange="{!c.change}"/>
</aura:component>

Child Component Controller:

({
    change: function(cmp,event,helper){

        cmp.get('v.testContact')[cmp.get("v.fieldName")] =  event.getSource().get('v.value');

    }
})

Parent Component Controller:

({
    recordSave : function(component, event, helper) {
        console.log(JSON.stringify(component.get('v.testContact')));
    }
 })

On this Way you can simply bind the values to an Object Instance and Validate. Also you can make it possible with giving recordId attribute to the lighthing:recordEditForm by just make the record as that testContact attribute.