How to pass parameter to recordEditForm on init

Question

I have 2 child components in a wizard the first on the first page the second on the second page. I pass a recordtype Id from the first component to the second component trough an event how do I pass this to the recordEditForm on Init for the second component. Currently I get an error : expected to get a string for recordTypeId but instead got null

Component

   <lightning:recordEditForm aura:id="form" 
                                  recordId="{!v.recordId}"
                                  objectApiName="{!v.genericObject}"
                                  recordTypeId= "{!v.Id}"  
                                  onsubmit="{!c.next}"
                                  >

Event

 getRecordtypeId: function(component, event, helper) {
        var RecTypeId = event.getParam("Id");
        console.log('The Id is: ' + RecTypeId);
        component.set("v.Id",RecTypeId);
    },

Answer 1

You should be using conditional rendering aura:if.

<aura:if isTrue="{!not(empty(v.Id))}">
    <lightning:recordEditForm aura:id="form" 
                                  recordId="{!v.recordId}"
                                  objectApiName="{!v.genericObject}"
                                  recordTypeId= "{!v.Id}"  
                                  onsubmit="{!c.next}"
                                  >
</aura:if>

This will make sure that record form is loaded only when Id is not empty.

Also the content of aura:if is rerendered when ever the condition becomes true. That is, when Id is set.