What is an Om component?

Question

Consider the following snippet of om code:

(fn [data owner]
    (reify
      om/IRender
      (render [_]
        (dom/p nil (:text data)))))

Question: Is the "Om component" this entire snippet, or is it merely the function's return value of the (reify ...) expression?

Answer 1

Generally, they are both referred to as the "component". The result of reify is the "object-y" thing, so in a sense it should be called the component, but the function is the thing that's named, so it's typically what's worth talking about.

Importantly, though, neither of these is a React component. Om creates and manages a React component for you. It's available here as owner.

Om Next removes this level of indirection, which helps with the terminology ambiguity a bit:

(defui HelloWorld
  Object
  (render [this]
    (dom/div nil "Hello, world!")))

(def hello (om/factory HelloWorld))

In this Om Next code, HelloWorld is an actual React component class, and its instances (generated with the function hello) are actual React component objects.