Скачать или смотреть How to Fix Instance Variables Not Appearing in Rails ActionMailer Preview

Discover how to resolve issues with missing instance variables in Rails ActionMailer previews, ensuring your emails display the correct content.
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This video is based on the question https://stackoverflow.com/q/73939968/ asked by the user 'Mark Locklear' ( https://stackoverflow.com/u/812660/ ) and on the answer https://stackoverflow.com/a/73940140/ provided by the user 'Haumer' ( https://stackoverflow.com/u/11042897/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Instance Variables Not Appearing in Rails ActionMailer and RSpec Preview

Working with Ruby on Rails, particularly with ActionMailer, can sometimes lead to unexpected issues. One common problem that developers encounter is the instance variables not displaying correctly in the email previews. In this guide, we will explore a specific issue where an instance variable is correctly set but fails to appear in the final output, and we will provide a clear solution to fix it.

The Problem

Imagine you're working on a Rails 7 application, and you have set up an ActionMailer intended to send progress emails to team leaders. Your code includes a method to generate these emails, set up with some relevant parameters. However, when you attempt to preview the email, you find that while one instance variable, @ leader_name, displays correctly, another, @ team_name, does not.

Here is the relevant code:

[[See Video to Reveal this Text or Code Snippet]]

And in your preview file, you have this:

[[See Video to Reveal this Text or Code Snippet]]

When you run the preview at rails/mailers/team/final_survey_nag_email, @ leader_name is correctly assigned a value, but @ team_name is not.

The Explanation

The root cause of the issue lies in how the parameters are being accessed in the mailer method versus how they are being set in the preview. In your final_survey_nag_email method, you are using params[:team] to assign the @ team_name variable. However, in your preview, you are setting it as team_name in the with method, which is indeed the correct approach.

What Needs to be Fixed

To resolve the missing variable issue, you should align the key used in the with method to correspond correctly to what your mailer method expects. Here’s how you can make that work:

Change the mailer method to correctly access the team_name. Using params[:team_name] instead of params[:team] will match the expected key.

Right now, your code looks like this in the mailer:

[[See Video to Reveal this Text or Code Snippet]]

Update it to this:

[[See Video to Reveal this Text or Code Snippet]]

With these adjustments, your mailer method will now look like this:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By ensuring that the keys you use in your mailer methods match those you’ve set in your preview methods, you can avoid issues with instance variables not appearing as expected. In this case, changing params[:team] to params[:team_name] will ensure that @ team_name gets assigned properly.

With these tips, you can enhance your Rails development experience, ensuring that your email previews render accurately and that your application behaves as intended. Happy coding!