1 x = 10  
2 puts "x is ten" if x == 10   # x is ten

1 x = 24
2 puts "You are not a teenager" unless age > 12 && age < 20  # You are not a teenager

1 x = 10  
2 puts "x is in the area" if x.between?(6, 10)   # x is in the area

1 # 使用do end来包裹逻辑代码块
2 5.times do puts "test" end     # testtesttesttesttest
3 
4 # 使用{ }来包裹逻辑代码快
5 5.times {puts "test"}               # testtesttesttesttest

1 1.upto(10) {|number| puts number}  
2 # 或者  
3 do |number| puts number end  
4 
5 #下面同样可以两种方式
6 10.downto(5) {|number| puts number}
7 0.step(50, 5) {|number| puts number} 

1 puts "abc" * 5  # abcabcabcabcabc
2 puts 'x' > 'y'      # false
3 puts 'x' < 'y'      # true
4 # 如果想得到一个字符ASCII码的值，使用 ? :
5 puts ?A --> 65      #  (在ruby2.3.0中好像还是会输出字符)
6 如果想要知道某个ASCII码对应的字符，可以使用数字 .chr方法来将其转换为字符：
7 puts 65.chr --> A 

 1 puts "This is a #{'bad ' *3} word" # This is a bad bad bad word   
 2 # 需要注意的是这一句整个必须用双引号括起来，而里面的bad则可以用单引号，双引号都可
 3 
 4 # 另外可以再插值中使用变量：
 5 x = 10
 6 y = 20
 7 # 如果想要输出 10 + 20 = 30
 8 # 直接输出的话，必须调用数字的 .to_s 方法，否则会报错：
 9 puts x.to_s + " + " + y.to_s + " = " + (x + y).to_s
10 # 而使用插值的话，输入为：
11 puts "#{x} + #{y} = #{x + y}" 

1 "foobarbar".sub("bar", "foo")  #  foofoobar 

1 x = "foobarbar"
2 puts x.sub(/^../, "hello")  # helloobarbar

1 x.scan(/./) do |letter| puts letter end 

1 # 例如找到下面字符串中的数字:  
2 "the car cost $1000 and that car cost $100".scan(/\d/) do |letter| puts letter end
3 # 会发现这时候是一个一个数字输出，这时就要用到 + 号表示一个或者多个了。
4 "the car cost $1000 and that car cost $100".scan(/\d+/) do |letter| puts letter end 

1  # the string has no digits
2 puts "the string has no digits" unless "hello, this is a test" =~ /[0-9]/  

1 puts "the string has no digits" unless "hello, this is a test".match('[0-9]')
2 x = "this is a test".match(/(\w+) (\w+)/)
3 x[0]    # this is
4 x[1]    # this
5 x[2]    #  is
6 x[3]    # nil 

1 irb(main):013:0> a = [1, 2,3]
2 => [1, 2, 3]
3 irb(main):014:0> a.join
4 => "123"
5 irb(main):015:0> a.join('|')
6 => "1|2|3"