显示ERB语法错误的堆栈跟踪.应用程序代码或ERB库有问题吗

Question

我正在学习Lynda.com课程中的ERB章节，Ruby Essential Training Part 3:Files，Formats，Templates，并且在ERB本身不断出现语法错误。当我输入此代码时：

#!/usr/bin/env ruby
#### Mail Merge ####
#
# Launch this Ruby file from the command line
# to get started
#
require 'erb'
require 'csv'
APP_ROOT = File.expand_path(File.dirname(__FILE__))
# files in current dir
template_path = File.join(APP_ROOT, 'letter_template.txt')
csv_path = File.join(APP_ROOT, 'us_presidents.csv')
template = File.read(template_path)
i = 0
CSV.foreach(csv_path) do |row|
next if row[0].start_with?('Number') # Header row
i += 1
@last_name = row[1]
@first_name = row[2]
state = row[6]
end_date = row[4] || Time.now.year
@title = "The History of #{state}"
@due_date = end_date
years = Time.now.year - @due_date.to_i
@fee = "$#{years * 365}.00"
letter = ERB.new(template).result(binding)
num = i < 10 ? "0#{i}" : i
filename = "letter_#{num}.txt"
filepath = File.join('letters', filename)
puts "-------"
puts filepath
puts letter
File.write(filepath, letter)
end

我收到这个错误消息：

Traceback (most recent call last):
15: from init.rb:20:in `<main>'
14: from /Users/andrekibbe/.rvm/rubies/ruby-2.7.0/lib/ruby/2.7.0/csv.rb:510:in `foreach'
13: from /Users/andrekibbe/.rvm/rubies/ruby-2.7.0/lib/ruby/2.7.0/csv.rb:658:in `open'
12: from /Users/andrekibbe/.rvm/rubies/ruby-2.7.0/lib/ruby/2.7.0/csv.rb:511:in `block in foreach'
11: from /Users/andrekibbe/.rvm/rubies/ruby-2.7.0/lib/ruby/2.7.0/csv.rb:1280:in `each'
10: from /Users/andrekibbe/.rvm/rubies/ruby-2.7.0/lib/ruby/2.7.0/csv.rb:1280:in `each'
9: from /Users/andrekibbe/.rvm/rubies/ruby-2.7.0/lib/ruby/2.7.0/csv/parser.rb:336:in `parse'
8: from /Users/andrekibbe/.rvm/rubies/ruby-2.7.0/lib/ruby/2.7.0/csv/parser.rb:823:in `parse_quotable_loose'
7: from /Users/andrekibbe/.rvm/rubies/ruby-2.7.0/lib/ruby/2.7.0/csv/parser.rb:49:in `each_line'
6: from /Users/andrekibbe/.rvm/rubies/ruby-2.7.0/lib/ruby/2.7.0/csv/parser.rb:49:in `each_line'
5: from /Users/andrekibbe/.rvm/rubies/ruby-2.7.0/lib/ruby/2.7.0/csv/parser.rb:52:in `block in each_line'
4: from /Users/andrekibbe/.rvm/rubies/ruby-2.7.0/lib/ruby/2.7.0/csv/parser.rb:871:in `block in parse_quotable_loose'
3: from /Users/andrekibbe/.rvm/rubies/ruby-2.7.0/lib/ruby/2.7.0/csv/parser.rb:1122:in `emit_row'
2: from init.rb:34:in `block in <main>'
1: from /Users/andrekibbe/.rvm/rubies/ruby-2.7.0/lib/ruby/2.7.0/erb.rb:905:in `result'
/Users/andrekibbe/.rvm/rubies/ruby-2.7.0/lib/ruby/2.7.0/erb.rb:905:in `eval': (erb):6: syntax error, unexpected '=', expecting end-of-input (SyntaxError)
;  = @due_date ; _erbout.<< "\n\n...**

堆栈跟踪中的所有内容都引用CSV和ERB行，所以我看不到任何可以纠正的内容。我是不是错过了什么？

更新：添加letter_template.rb：

Dear <%= @first_name %> <%= @last_name %>,
The following library book is overdue.
"<%= @title %>"
Due: <% = @due_date %>
Overdue fee: <%= @fee %>
Thank you for your prompt attention to this matter.

Answer 1

堆栈跟踪显示来自ERb的行，因为ERb代码是正在执行的代码。

虽然理论上问题可能出现在ERb本身或您的模板中，但考虑到ERb每天都有数千名开发人员和应用程序使用，问题更可能出现在模板中。