ActionMailer 参数未通过预览

Question

I'm new to Rails Action Mailer and when configring my first email, I get this error after visit http://localhost:3000/rails/mailers/user_mailer/confirm_email:

undefined method '[]' for nil:NilClass @user = params[:user]

My code:

class UserMailer < ApplicationMailer
  def confirm_email
    @user = params[:user]
    mail to: "to@example.org"
  end
end

class UserMailerPreview < ActionMailer::Preview
  def confirm_email
    UserMailer.with(user: User.first).confirm_email
  end
end

If I change code to this:

class UserMailer < ApplicationMailer
  def confirm_email(user)
    @user = user
    mail to: "to@example.org"
  end
end

class UserMailerPreview < ActionMailer::Preview
  def confirm_email
    UserMailer.confirm_email(User.last)
  end
end

The preview class is located in test/mailers/preview, outside of the app folder.

I receive this:

wrong number of arguments (given 0, expected 1)

I cant understand, what I'm doing wrong?

My rails version is 6.0.3.5

Answer 1

Provided you are positive you have at least one User record in your database, I would try the following, which is a mix of your attempts.

class UserMailer < ApplicationMailer
  def confirm_email(user)
    @user = user
    mail to: "to@example.org"
  end
end

class UserMailerPreview < ActionMailer::Preview
  def confirm_email
    UserMailer.with(user: User.first).confirm_email
  end
end