Loading a custom component into a Visualforce page dynamically

Question

I have a visualforce page that I would like to inject custom components (header and footer) if they exist into the page.

According to the docs Creating and Displaying Dynamic Components I can instantiate a custom component like so

Component.c.MyCustomComponent myDy = new Component.c.MyCustomComponent();

but I don't know the name of MyCustomComponent ahead of time, and as mentioned it may not exist. Is there an equivalent of something like:

Component myDy = Type.forName('c:MyCustomComponent'); //does not compile ;)

I am not tied to dynamic visualforce, If anyone knows of an alternative solution I would be very interested.

Answer 1

I have developed a solution, there are shortcomings that I hope someone knows the solution too. The following code snippet allows loading of a visualforce component onto a page dynamically.

public class MyController {

    public transient ApexPages.Component headerComponent { get; private set; }

    public MyController() {
        Type t = Type.forName('Component.c.MyCustomComponent');
        if(t != null) {
            this.headerComponent = (ApexPages.Component)t.newInstance();
        }
    }
}

.

<apex:dynamicComponent componentValue="{!headerComponent}" />

The shortcoming is that, so far as I can tell parameters can not be passed. I would be happy to be proved wrong on this point :)

Credit goes to @Peter for steering me in the right direction on this.

Answer 2

I'm just learning about the Type class, but looking at the docs, I would think the syntax you would want to use is:

Type.forName('Component.c.MyCustomComponent');

But as I play with this more, I think the greater problem is what to pass it into.

Component, is either not a concrete class, or Apex is not given access to it.

The docs explicitly state that apex:component is not represented in dynamic Apex. So no dice there. Still, I tried: Component.Apex myComp; (seemed to confuse the hell out of the compiler) Component.Apex.Component; (invalid type)

Finally, this compiles, but throws a null pointer exception:

Type t = Type.forName('Component.c.MyCustomComponent'); Object myComp = (Object) t.newInstance();

And Object, while it exists, probably won't bind to your page, in the end.

I think you've reached one of the limits of the platform, unfortunately.