Using devcards with re-frame

Devcards is awesome, particularly for beginners or anyone exploring Reagent or Om.

Re-frame is a great way to design large Reagent applications -- however, since there is only one app-db that holds all the state, it may not be obvious how you can use it with devcards.

I found an inelegant way to handle it -- and I'm curious if it would make sense to put it in the wiki

I also think that this pr or something like it might allow for a more idiomatic solution #97 curious of your thoughts.
### When you want to see the entire state of your re-frame db to appear in a card

require [re-frame.db :refer [app-db]] in the ns, then put that in as the db of your reagent card.
### When you want to only see some component of the state,

Def a subscription to that component of the state, and use that as the card's db

_Here's an example:_
1. Create a handler to update app-db

```
(register-handler
:demo1
(fn [_ _]
{:status "great"
:number 42}))

```

this just replaces the app-db with the map
1. dispatch that action

```
(dispatch [:demo1])

;you can deref the app-db to make sure it worked
@app-db
; should be {:status "great" :number 42}

```

if you have a card that only needs the status, register a sub for that

```
```

(register-sub
:status
(fn [db _](reaction %28:status @db%29)))

```
;; then def that subscription

(def lildb
(subscribe [:status]))

;; now you have a subset of the db you can include in a card

@lildb
;; should show "great"

(defcard-rg status-card
[:h1 (str "I'm" @lildb "today")]
lildb
{:inspect-data true})
`
```
## But wait -- there is a problem with this -- the problem being that changes to the app-db don't get reflected in the def'd subscription

--- in your devcards use that def'd subscription as the card's db, and in place of where you'd define the subscription in your component

Example

```
(defn swapper []
(let [s (subscribe [:status])]
[:div
(pr-str @s)
[:button {:on-click #(dispatch [:change-status "fantastic"])} "fantastic"]
[:button {:on-click #(dispatch [:change-status "terrible"])} "terrible"]]))

(defcard-rg status-card
[swapper]
lildb
{:inspect-data true
:history true})

```

when the dispatch buttons are clicked, the value of @s will change, but not the card's db. Why? The card's db isn't being directly altered, or called from within the card -- so if you want it to match up appropriately, you have to do things like this

```
(def lildb
(subscribe [:status]))

(defn swapper []
[:div
(pr-str @lildb)
[:button {:on-click #(dispatch [:change-status "fantastic"])} "fantastic"]
[:button {:on-click #(dispatch [:change-status "terrible"])} "terrible"]]))
```

Unfortunately, while doing that will allow you to walk the history back and forth, the history you're walking back and forth can fall out of sync with the actual app-db -- so you have to be cautious.

Is there a better way to do this?

Start with the app-db, subscription, and devcard examples in the issue, then read the discussion referenced by #97. Determine whether the desired outcome is wiki guidance or a more idiomatic devcards/re-frame integration; done requires an agreed approach that keeps card data and re-frame state understandable and synchronized.

Written by the indexing model from the issue text.