"form_for" vs. ".form" vs "f = form_for"

Phoenix Forum Questions / Help
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I know this thread is old, but I was struggling with the same question, so I’ll post the answer in case anyone else comes across this thread like I did.

tl;dr:

  • form_for should no longer be used and will eventually be removed from Phoenix.
  • In LiveView, use <.form for={@form}> where @form is a Phoenix.HTML.Form struct (generally created using to_form). Don’t use :let.
  • Outside of LiveView, you can also pass a changeset or map to for, and it’ll be converted to a Form which can be captured with :let. (This approach is also technically possible in a LiveView, but it’s discouraged because it makes change tracking less efficient.)

The second and third points are made clear in the docs for form/1. The first point was confirmed to me by none other than Chris McCord; I wrote about it here:

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