app/views/shared/_tweet_form.html.erb
<div class="tweet-box">
<%= form_with model: current_user.tweets.new do |form| %>
<div class="field">
<%= form.text_area :content, placeholder: "Compose new Tweet..." %>
</div>
<div class="btn-toolbar justify-content-between">
<div class="btn-group">
<%= form.file_field :image, accept: "image/jpeg,image/gif,image/png" %>
</div>
<div class="btn-group">
<%= form.submit "Post", class: "btn btn-large btn-primary" %>
</div>
</div>
<% end %>
</div>