In my app users can list someone's instagram profile, but they would have to copy and paste the entire url in the form.
<%= f.url_field :url,required: true,label: "URL (required)" %>
How do i set the default url in my form as instagram.com/ so that they would only need to enter the username?
You can just ask for username and later in controller/form model remove @
(and whole 'http://instagram.com/' prefix if someone pastes url instead of username)
<%= f.text_field :instagram_username, required: true, label: "instagram.com/" %>
Controller something like:
obj = Model.new(model_params)
if (username = params.dig(:some_model, :instagram_username))
username = username.gsub(%r{https?://instagram.com/}, '').gsub(/^@/, '')
obj.url = "https://instagram.com/#{CGI.escape username}"
end