大小读取和写入文件和条件语句

Question

初学Ruby。正在做一个读写文件的练习。

name_number = {

}

File.open("book.txt", 'a') do |file| 
  name_number.each do |name, number| 
    file.write ("- #{name} #{number}\n")
  end
  file.close
end

File.open("book.txt", "r") do |file|
  if file.size < 1
    puts "There are no people in the book."
  end

  File.open("book.txt", "r") do |file| 
    puts file.read
  end
end

所以输出“书中没有人”。当文件为空时。

所以如果我们添加一些人...

name_number = {
  "Bill" => 87987,
  "Kevin" => 78912
}

File.open("book.txt", 'a') do |file| 
  name_number.each do |name, number| 
    file.write ("- #{name} #{number}\n")
  end
  file.close
end

我在想怎么让它说

“有一个人”为1 和“有些人”表示任何超过 1 的东西。

我想我需要一个像这样的 elsif 声明，（但显然这行不通，但也许你可以看到我想要实现的目标？）。

File.open("book.txt", "r") do |file|
  if file.size < 1
    puts "There are no people in the book."
  elsif file.size == 1
    puts "There is an entry in the book."
  elsif file.size == 2
    puts "There are two entries in the book"  
  end

  File.open("book.txt", "r") do |file|
    puts file.read
  end
end

我肯定漏掉了什么。我想知道是否有人可以指出正确的方向？

Answer 1

file.size 给出字节数。你可能想要 file.readlines.size

Answer 2

我发现如果我将 .count 与 readlines 一起使用，我就能解决我的问题！

更新代码

File.open("book.txt", "r") do |file|
  number = file.readlines.count
    if number < 1
      puts "There are no people in the book."
    elsif number == 1 
      puts "There is one person in the book"
      File.open("book.txt", "r") do |file| 
        puts file.read
      end
    elsif number == 2
      puts "There are two people in the book."
      File.open("book.txt", "r") do |file| 
        puts file.read
      end
    elsif number >= 3
      puts "There are some entries in the book."  
      File.open("book.txt", "r") do |file| 
        puts file.read
      end
    end
  end

Answer 3

要获得您需要阅读的文件的行数。如果可能，您希望避免多次读取文件。

假设文件不是太大，您可以 gulp 它 成一个数组，使用 IO::readlines:

 arr = File.readlines("book.txt")     
 puts case arr.size
 when 0
    "There are no people in the book."
 when 1 
    "There is one person in the book"
 when 2
    "There are two people in the book"
 else
    "There are some entries in the book"
 end  
 puts arr

或者，您可以 gulp it 到一个字符串中，使用 IO::read:

 str = File.read("book.txt")     
 puts case str.count("\n")
 when 0
    "There are no people in the book."
 when 1 
    "There is one person in the book"
 when 2
    "There are two people in the book"
 else
    "There are some entries in the book"
 end  
 puts str

如果文件太大，您需要一次一行地阅读它，您可以使用IO::foreach。但是，这确实需要两次遍历文件。

 puts case File.foreach("book.txt").count
 when 0
    "There are no people in the book."
 when 1 
    "There is one person in the book"
 when 2
    "There are two people in the book"
 else
    "There are some entries in the book"
 end  
 File.foreach("book.txt") { |line| puts line }

大小读取和写入文件和条件语句

Size Reading and Writing to File and conditional statements

ruby

size

file