Hi Thomas - yes, you are right. The example I provided is all pain/no-gain in
terms of macros. However, future plans will require manipulating the invocation
of (for example form/text and form/number) before they are evaluated.
Having said all of that, that repeated ‘form’ does bug me a bit :-). I do
absolutely agree that the cognitive overhead of the macro isn’t justified here.
> On 2 Oct 2015, at 14:29, Thomas Heller <th.hel...@gmail.com> wrote:
>
> Have you tried NOT using a macro at all? This code does not need to be a
> macro at all if you ask me.
>
> Just a little sketch but things could look just about the same without any
> macros at all:
>
> (let [form {:editing? true
> :values form-values
> :validation validation-report
> :on-change handle-form-change}]
> (form/tag form
> (form/text form :name)
> (form/number form :age)))
>
>
> ;; in-ns 'form
>
> (defn text [form field]
> [text-component {:id field
> :value (get-in form [:values field])
> ...}])
>
> (defn tag
> [{:keys [editing?] :as form} & children]
> (into [:div.form.horizontal
> {:class (if editing? "editing" "editable")}]
> children))
>
>
> Use macros very sparingly, most of the time data and functions are just
> better.
>
> Just my 2 cents,
> /thomas
>
> On Wednesday, September 30, 2015 at 10:29:30 PM UTC+2, Colin Yates wrote:
> Hi all,
>
> I am banging my head against the wall - I think it is obvious but I have
> started too long:
>
> The use-case is that I want a form which takes a set of children. The form
> also takes in some form-wide state, like the form-wide validation, the values
> for each item etc. I want the macro, for each child, to decorate that child
> by extracting the validation errors and value from the form-wide state.
>
> So, assuming:
> - validation looks like {:name "Duplicate name" :age "You must be at least
> 0"}
> - form-values looks like {:name "a-duplicate-user" :age -1}
>
> then my form might look like:
>
> (form {:editing? true :values form-values :validation validation-report
> :on-change handle-form-change}
> [form/text {:id :name}]
> [form/number {:id :age}])
>
> After the macro I want the following code:
>
> [:div.form.horizontal
> {:class "editing"}
> [form/text {:id :name :value "a-duplicate-user" :errors "Duplicate name"
> :on-click (fn [e] (handle-form-change :name (-> e .target .value])]
> [form/number {:id :age :value "-1" :errors "You must be at least 0"
> :on-click (fn [e] (handle-form-change :age (-> e .target .value))]]
>
> However, ideally the macro would _not_ emit the contents of the input as
> literals but would emit code that inspects the provided parameters at
> run-time (i.e. rather than :value "a-duplicate-user" I would much prefer
> :value (-> state values :name) as that will allow me to pass in an atom for
> example.
>
> I have tried so many variations and evaluating the state (e.g. (:editing?
> state)) works fine as the emitted code has the destructured values, but that
> doesn't work for an atom.
>
> Here is my attempt at trying to emit code that interrogates the provided
> parameter.
>
> (defmacro form [state & elements]
> (let [state# state]
> `[:div.form.horizontal
> {:class (if (:editing? state#) "editing" "editable")}
> ~@(map (fn [[_ {:keys [id]} :as child]]
> (update child 1 assoc
> :editing? (:editing? state#)
> :value `(-> (:values state#) 'deref (get ~id))
> :on-change `(fn [e#]
> (js/console.log "E: " (cljs.core/clj->js
> e#))
> ((:on-change state#) ~id (-> e# .-target
> .-value)))))
> elements)]))
>
> The error I am getting is that there is such var as the gen-sym's state# in
> the namespace.
>
> The generic thing I am trying to do is remove the boilerplate from each of
> the items in the form.
>
> Any and all suggestions are welcome.
>
> Thanks!
>
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