Question

我已编写以下代码以检查用户输入字符串是否存在于文件中。该方法是 checkinfile 。我正在使用while循环逐行读取并执行.eql？检查它是否匹配。但即使我输入匹配值，该方法返回false。有人可以帮帮我吗？

    class School
    #Declaration of Global Variable. The file is the file database used for storing names of the students.
    $filename="studentsdatabase"
    #All the methods for the class Student are declared in this area

    #Method : Show Menu
      def showmenu
        puts "\e[H\e[2J"
        print "*" * 100
        print "\n"
        print "-"*44 + "MENU OPTIONS" +"-"*44 + "\n"
        print "*" * 100
        print "\n"
        print "1. Add a student data\n"
        print "2. Verify if the student is present in the database\n"
        print "3. View the list of students in the database"
        print "Enter your option(1/2) :"
        option=gets.chomp.to_i
        return option
      end

    #Method : Ask the details of the students
      def askdetails
        puts "\e[H\e[2J"
        print "How many students are there\n"
        n = gets.chomp.to_i - 1
        print "Enter names one by one\n"
        names=Array.new(n)
        for i in (0..n)
          names[i]=gets.chomp
        end
        return names,n
      end

      def showdetails(names,n)
        for i in (0..n)
          puts names[i]
        end
      end

    #Method : Write into file database
      def write2file(names,n)
      studnamesfile=File.open($filename,"a")
        for i in (0..n)
         studnamesfile.puts names[i]
        end
      end

    #Method : This method verifies the user input in the file database.
      def checkinfile
        puts "\e[H\e[2J"
        print "Enter the name of the student: "
        studname=gets.chomp
        somefile=File.open($filename,"r")
        counter=1
        occur=0
        while(line=somefile.gets)
          val = puts.eql? studname
           occur=occur+1
        puts "#{counter}: #{line}"
        puts "#{val}"
        counter = counter + 1
      end
        somefile.close

      end
    #This is the end of Class Student declaration
    end

    #Main Program starts here
    stud=School.new
    option=stud.showmenu
    if option==1
    names,n = stud.askdetails
    stud.write2file(names,n)
    else
    puts "\e[H\e[2J"
    stud.checkinfile
    end

Answer 1

这是包含eql?：

的行

val = puts.eql? studname

在此处检查调用方法puts的返回值是否等于studname。 puts始终返回nil，因此，val可能始终为false。

要解决此问题，您应该使用line：

val = line.eql? studname

此外，您可能希望确保没有影响测试的尾随换行符：

val = line.strip.eql? studname.strip

在ruby中逐行比较文件中的字符串

1 个答案: