Rails 5邮件视图each循环内容不显示问题求助

Hey there! Let's figure out why that loop in your mailer view isn't rendering—you’ve already done the smart thing by confirming the @order.carted_activities collection exists, so we can rule out the data not being passed through entirely. Here are the most common fixes to try:

1. Double-Check Your ERB Output Syntax #

The #1 culprit here is usually forgetting to use <%= for content you want to display inside the loop. The each loop itself uses <% (no equals sign), but any dynamic content inside needs <%= to render to the page.

For example, this won’t show anything:

<% @order.carted_activities.each do |carted_activity| %>
  <p>Activity: carted_activity.name</p>
<% end %>

But this will work:

<% @order.carted_activities.each do |carted_activity| %>
  <p>Activity: <%= carted_activity.name %></p>
  <p>Quantity: <%= carted_activity.quantity %></p>
<% end %>

2. Verify the Collection Actually Contains Items #

Even though you see the ActiveRecord_Associations_CollectionProxy output, that doesn’t guarantee there are actual records in it. Add a quick debug line above the loop to check:

<p>Total carted activities: <%= @order.carted_activities.size %></p>

If this outputs 0, you need to make sure the carted_activities are being saved to the database before you trigger the mailer. For example, if you’re calling the mailer right after creating the order but before saving the associated carted activities, they won’t exist in the collection when the email is generated.

3. Ensure Associations Are Loaded #

Sometimes Rails lazy-loads associations, and in the context of a mailer, that can cause issues if the database connection isn’t available when rendering the template. Preload the association in your mailer method to fix this:

# In your OrderMailer class
def order_confirmation(order)
  @order = order.includes(:carted_activities) # Preload the association
  mail(to: order.user.email, subject: "Your Order Confirmation")
end

4. Clear Template Caches (Dev Environment) #

Letter_opener can sometimes cache old versions of your template, even after you’ve made changes. Try restarting your Rails server, then resend the email to see if the loop renders.

5. Check for Hidden Errors #

If none of the above works, look at your Rails development logs (log/development.log) when the email is sent. Sometimes an error inside the loop (like a nil attribute, e.g., carted_activity.activity being nil) will silently fail and prevent the loop from rendering. The logs will show any exceptions that occur during template rendering.

Give these steps a shot—odds are it’s one of the first two issues. Let me know if you need more help narrowing it down!

内容的提问来源于stack exchange，提问作者Jacinta Lim