堆栈跟踪显示 ERB 语法错误是app代码问题还是ERB库问题？

编程问答 2022-05-31

问题描述

我正在学习 Lynda.com 课程 Ruby Essential Training Part 3: Files,Formats,Templates 中的 ERB 章节，并且不断收到似乎是 ERB 本身的语法错误。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

我收到此错误消息：

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了 CSV 和 ERB 行，因此我看不到任何可以纠正的内容。我错过了什么吗？

更新： letter_template.rb 添加：

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.

解决方法

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在 ERb 本身或您的模板中，但鉴于 ERb 每天被成千上万的开发人员和应用程序使用，问题更可能出在您的模板中。 /p>

erberberbrubyrubyruby