Dynamic Component Problem with TypeMethods

[dji973]

Hello everyone,

I created this post because I have a problem. I want to create a dynamic component to add it to a page. So here is my configuration :

TabLayoutLead

<apex:page id="tabLayout" >

...

     <c:myDynamicComponent compToAdd="QuoteComponent" contAssoc="QuoteComponentController" extName="ClassExtensionName"/>

...

</apex:page>

MyDynamicComponent

<apex:component controller="MyDynamicController" >

  <apex:attribute name="compToAdd" description="The component to dynamically add to the stage"   type="String" required="true" assignTo="{!compToAdd}" />
  <apex:attribute name="contAssoc" description="The controller associated to the component"   type="String" required="true" assignTo="{!contAssoc}" />
  <apex:attribute name="extName" description="The extension label associated to the compoonent to get the regular or custom component" type="String" required="true" assignTo="{!extName}" />

  <apex:dynamicComponent id="theParent" rendered="false" componentValue="{!addComponent}"/>

</apex:component>

MyDynamicController

global class MyDynamicController {

  public Type t { get; set; }
  public String compToAdd { get; set; }
  public String contAssoc { get; set; }
  public String extName { get; set; }

  public MyDynamicController()

  {

  }

  public ApexPages.Component getAddComponent()

  {

    if (extName != 'Default')
      compToAdd = compToAdd + extName;
    t = Type.forName(compToAdd);
    return (ApexPages.Component) t.newInstance();
  }
}

My final goal is, having a list of custom components, to be able to create them on my page by just calling one single line. So in MyDynamicComponent, I create the new component using the apex:dynamicComponent. But I have a problem, because in my controller, the function called dynamicComponent.getAddComponent(), when creating a newInstance using TypeMethods, throws a NullPointerException because  t = Type.forName(compToAdd) returns null. I've figured out that TypeMethods are for Classes only and not Components. Then I wanted to create a Class which extends ApexPages.Component so I can use it with the TypeMethods but I then got the following error "Error: Compile Error: Parent class has no 0-argument constructor for implicit construction".

So I wanted to know, can I technically do what I want to do ? I come from a Flex/Java world so maybe I'm at the limit of Salesforce.

If I can do it, do you have any suggestions for me please, maybe you already did this.

Thank you very much.

[sfdcfox]

You can create a wrapper class/Interface. Here's one possible solution:

// Just need 1 of these.
global Interface ComponentReference {
  ApexPages.Component getInstance();
}

// Need 1 per component.
public class MyComponent1Reference implements DynamicComponentReference {
  ApexPages.Component getInstance() {
    return new Component.mynamespace.MyComponent1();
  }
}

public void dosomething() {
  Type t = Type.forName('mynamespace','MyComponent1Reference');
  ApexPages.Component cr = t.newInstance().getInstance();
}

The value of this is fairly limited in scope; you need a way to configure elements, and because of the nature of binding, this might blow up later.

Your Flex background has served you well; regrettably, Apex Code is significantly more restricted in terms of dynamic types than Flex is.

[dji973]

Thanks for the quick reply. I'll try this and I let you know

[dji973]

Thanks. Your solution works very well. To be a little bit more tricky, what I did is that in my controller I added this getInstance function so I dont need to create any more classes.

Now I have one more question. Apparently, the dynamicComponent is added to the Page between between controller's constructor and variable assignment. Which means that, in my dynamicComponent adding, I cannot used fields and attributes that I need to customize my component.

Do you know any way to get these attributes before the dynamicComponent's componentValue is called please ?

Thank you.

[sfdcfox]

Getters are called after setters, so you should be able to see the values and attributes you have. Just remember to not set any variables in a getter method, and do not depend on any values being available in setter methods. If you're still having problems, maybe you could post an example?