I added console statements in various methods of component

I see the render console statement called first

and then the component did mount

and I dont see the component will receive props called after

but the component is rendered with new re-frame subscription data

@rnagpal that's not enough information to go on

What more information should I add @pesterhazy

why do you assume that component-will-receive-props will be called?

do you actually change the props?

Here is the code

(fn [opts]
  (let [data-sub (re-frame/subscribe [::data-sub])
        show-loading? (reagent/atom false)]
    (reagent/create-class
      {:display-name "generic-loading-component"
       :component-did-mount
       (fn component-did-mount [_]
         (js/console.log "In component-did-mount of loading")
         (when-not @show-loading?
           (js/setTimeout #(when-not @node-events
                             (reset! show-loading? true))
                          100)))
       :component-will-receive-props
       (fn component-will-receive-props [_]
         (js/console.log "In component-will-receive-props of loading")
         (when @node-events
           (js/console.log "reset show loading to false")
           (reset! show-loading? false)))

       :component-will-update
       (fn component-will-update [_]
         (js/console.log "In component-will-update of loading")
         (when @node-events (js/console.log "reset show loading to false")
                            (reset! show-loading? false)))

       :reagent-render
       (fn [opts]
         (js/console.log "In Render of loading")
         (if @show-loading? [:div "LOADING"]
                            [show-data @data-sub opts]))})))

@pesterhazy

yeah looks like you're not actually changing the props, opts

for background, there are three ways to cause a component to rerender in React

1. this.state 2. this.props 3. manually calling render on the component again

Reagent typicaly doesn't use 1; 2 is pretty obvious

So in case of subscription does the react lifecycle not come into picture ?

If you change a ratom, reagent does 3

yes it's still a lifecycle change, but comoponent-will-receive-props won't be called

component-will-update should be called though

one trick is to use an outer comp/inner comp pattern

you'd pass the changes to the inner component, which then gets an explicit prop change

another option is to inspect your ratom in component-will-update

depends on what you want to achieve really

@pesterhazy can you please point me to the source code that is responsible for updating the component based on subscription

I would want to understand how exactly the component will behave

if subscription data changes

Just like you mentioned component-will-update should be called though

you are right

I think it's here: https://github.com/reagent-project/reagent/blob/master/src/reagent/impl/component.cljs#L140

it's a batch/queue-render call wrapped in a Reaction

this enqueues the component to be re-rendered at a later point, e.g. at the next tick

@rnagpal ^^

Thanks a lot @pesterhazy. Going through the code now

it's a bit cryptic 🙂

@rnagpal this may help https://github.com/Day8/re-frame/wiki/When-do-components-update%3F#lifecycle-functions