alexslade
I’ve got a custom button in a form (choosing an image from a library). I’m struggling to write an event handler for that button. I started with update_params/3 as this seems to indicate that it should be used for such a situation.
This can be useful for things like customized inputs or buttons, that have special handlers in your live view. For example, if you have an appointment that expresses a list of available times in the UI, but the action just takes a single
timeargument, you can make each available time a button, like so:
<.button phx-click="time-selected" phx-value-time="<%= time %>" />
That function works if the form has been interacted with in some way (e.g. change handler that has populated “params” on the form).
But if this button click is the first interaction, the form’s params have not been established yet, which causes issues when update_params does validate etc which seems to expect a full list of params for the form. For example, if there is some other form field that is required (in my case: “Name”), after running update_params that field will now be blank and will fail validation, and try to clear that field.
I’ve tried the only_touched option and some other functions, like using “validate” with partial params, but I can’t find a solution.
I suspect I’m misunderstanding how the form should be used. Any tips?
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zachdaniel
Yeah, so the problem effectively is that there is a sort of bidirectional communication here. The underlying form data structure doesn’t know what fields you are or are not going to include in the UI, those fields get their defaults from the form, and then on type the client sends it back to us. Until then, we don’t have a full picture of what params looks like. It isn’t ideal.
You could likely do this with a bit of js on the button.
EDIT:
"validate"probably wouldn’t be what you want, you’d want to trigger some input as if it was typed into potentially, or find some way to trigger the phx-change hook etc. I’m sure it can be done but I can’t recall howAlso Liked
alexslade
Thanks for confirming. I’ll find another way around. Likely modifying the form inputs for now, as we don’t need validation when this image is changed. I also think our form should be factored to split this stuff up more, instead of having complex state across many entities with different validation rules, so we’ll do that if we need to make this more sophisticated.