如何解决“无法将nil转换为String(TypeError)"在Ruby中读取csv文件时? [英] How to get around "Can't convert nil into String (TypeError)" when reading a csv file in Ruby?

问题描述

我正在开发一个程序，该程序最终将比较两个.csv文件并打印出这两个文件之间的所有差异.但是，当我读取其中一个文件时，目前还无法解决无法将nil转换为String(TypeError)"的问题.

I am working on a program that will eventually compare two .csv files and print out any variances between the two. However, at the moment I can't get past a "can't convert nil into String (TypeError)" when reading one of the files.

这是有问题的csv文件中的示例行:

Here is a sample line from the problematic csv file:

11/13/15,11:31:00,ABCD,4000150097,1321126281700ABCDEF,WR00002440,,,4001,1392,AI,INTERNAL RETURN,INBOUND,,ABCDEF

这是到目前为止的代码:

And here is my code so far:

require 'csv'
class CSVReportCompare

  def initialize(filename_data, filename_compare)
    puts "setting filename_data=", filename_data
    puts "setting compare=", filename_compare
    @filename_data = filename_data
    @filenam_compare = filename_compare
  end

  def printData
    @data = CSV.read(@filename_data)
    puts @data.inspect
  end

  def printCompareData
    @compareData = CSV.read(@filename_compare)
    puts @compareData.inspect
  end

  def compareData

  end

end

c1 = CSVReportCompare.new("data.csv", "compare_data.csv")
c1.printData
c1.printCompareData

无论如何，有没有办法解决该错误?

Anyways, is there a way to get around the error?

推荐答案

您的initialize方法中有错字:

@filenam_compare = filename_compare
#-------^ missing "e"

因此，您设置了错误的实例变量.实例变量在首次使用并初始化为nil时创建，因此稍后，当您尝试访问@filename_compare时，将创建名称为正确的实例变量，其值nil.

So you're setting the wrong instance variable. Instance variables are created when they're first used and initialized to nil so later, when you try to access @filename_compare, the instance variable with the correct name is created and has a value of nil.

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