ruby language

2022-07-06

是真的方便

1. 循环？

    5.times do
       
    	print 'hello world!'
       
    end
   

2. 数学计算？

   2 + 3

3. 打印？put something on the screen

   puts xxx

4. 重复多个字符串？

   "ruby" * 5

5. 类型抓换？

   to_s 转换为字符串

   to_a 转换为数组

   to_i 转换为整数

6. 定义数组？

   arr = [1,2,3]

7. 数组长度？最大值？最小值？反转？排序？

   [12, 47, 35].length

   [12, 47, 35].max

   [12, 47, 35].min

   [12, 47, 35].reverse

   [12, 47, 35].sort!

   …

8. 数组排序是否修改原数组？

   arr = [1,2,3]

   arr.sort! 加! 标记在原数组上排序

9. 读取、存放数组

   puts arr[1]

   arr[1] = 4

10. 一些字符串操作方法

    name = "ruby is nice"

    name.gsub("nice", "so nice")

    name.reverse

    name.lines

11. 方法链式调用？

    str = "Hello world!\n I am Ruby!"

    str.lines.reverse.join

12. hash

    books = {}

    books["The deep end"] = :abysmal

    books["Living colors"] = :mediocre

    puts books

    puts books.length

    puts books["The deep end"] ：取value

    books.keys

    books.values

13. : 的含义？

    单词前加:, 会让这个单词在内存里只存一份。这样节省内存。

    但是加上: 就不再是简单的字符串了。

14. 分支？

    if 1 < 2
      puts "It is true: 1 is less than 2"
    end
        
    puts "It is true: 1 is less than 2" if 1 < 0
    

15. What does the question mark at the end of a method name mean?

    • It is a code style convention; it indicates that a method returns a boolean value (true or false) or an object to indicate a true value (or “truthy” value).

      The question mark is a valid character at the end of a method name.

      https://docs.ruby-lang.org/en/2.0.0/syntax/methods_rdoc.html#label-Method+Names

      From : https://stackoverflow.com/questions/1345843/what-does-the-question-mark-at-the-end-of-a-method-name-mean-in-ruby#:~:text=It is a code style,html%23label-Method%2BNames

16. 打印替换

    #{} 里面放变量，比如 #{name}

17. 面向对象：定义类

    class Blurb
    	attr_accessor :content, :time, :mood
    	def initialize(mood, content="")
    		@time    = Time.now
    		@content = content[0..39]
    		@mood    = mood
    	end
    end
    

    这里的@ ，和使用. 调用意思一样。在类里面调用对象的变量用@ ，类外用.