Ruby：String与String的比较失败（ArgumentError）

Question

这是我的红宝石代码：

books = ["Charlie and the Chocolate Factory", "War and Peace", "Utopia", "A Brief History of Time", "A Wrinkle in Time"]

books.sort! {

  |firstBook, secondBook|
  boolean_value = firstBook <=> secondBook
  print "first book is =  '#{firstBook}'"
  print " , second book is = '#{secondBook}'"
  puts  " and there compare result is #{boolean_value}"

}

问题：

1. 此代码运行单次迭代，然后出现错误in 'sort!': comparison of String with String failed (ArgumentError)
2. 当 firstbook =＆＃34; Charlie和巧克力工厂＆＃34; 然后 secondBook应该是＆＃34; War and Peace＆＃34; 但是代码选择的＆＃34;乌托邦＆＃34;比较。为什么？

Answer 1

确保从传递给sort!的块中返回比较结果。

目前，您返回nil（最后一个语句的返回值，puts），这会导致不可预测的结果。

将您的代码更改为：

books = ["Charlie and the Chocolate Factory", "War and Peace", "Utopia", "A Brief History of Time", "A Wrinkle in Time"]

books.sort! {

  |firstBook, secondBook|
  boolean_value = firstBook <=> secondBook
  print "first book is =  '#{firstBook}'"
  print " , second book is = '#{secondBook}'"
  puts  " and there compare result is #{boolean_value}"

  boolean_value  # <--- this line has been added
}

一切都会奏效。

---

Offtopic，一些挑剔：

• 在Ruby中，惯例是在变量名中用下划线分隔单词。例如，您应该重命名firstBook - ＆gt; first_book
• 在命名变量时应该非常小心。变量boolean_value在这里有点误导，因为它不是true或false，而是-1，0或1。