NoMethodError: nil:NilClass 的未定义方法“body”（测试失败）

Question

我得到一个失败（在 premailer-rails 中）这样说：

ActionMailer::Base delivery delivers email with inlined CSS
     Failure/Error: body = mail.html_part.body.to_s

     NoMethodError:
       undefined method `body' for nil:NilClass
     # ./spec/integration/delivery_spec.rb:9:in `block (2 levels) in <top (required)>'

这里是spec/integration/delivery_spec.rb：

require 'spec_helper'

describe 'ActionMailer::Base delivery' do
  it 'delivers email with inlined CSS' do
    WelcomeMailer.welcome_email("world").deliver_now

    mail = ActionMailer::Base.deliveries.last
    expect(mail).to be_present
    body = mail.html_part.body.to_s
    expect(body).to be_present
    expect(body).to include(%{<p style="font-size: 12px;">Hello world</p>})
  end
end

不确定发生了什么；为什么会出现 NoMethodError？ ：/

Answer 1

html_part是设置如果你发送多部分邮件，你可以调用mail.body.to_s代替，应该设置。