输出文本

puts "a" + "b"; # => "ab" puts 1 + 2; # => 3 puts "1" + "2"; # => "12"

输出时不换行

print "Hi" print "Bob"

屏幕输出为 "HiBob"

输出多个字符串连接

print "Bye", " John" # => "Bye John"

计算总和与平均值

total = 1 + 2 + 3; # => total 的值为 6 average = total / 3; puts average; # => 2

在字符串中插入变量

puts "total is " + total.to_s puts "average is #{average}"

获取用户输入并转换为整数

input = gets.chomp.to_i

处理负分情况

score = -70

if score < 0 puts score = 0 # 不能有负分 end

使用 unless 处理负分情况

score = -70

unless score >= 0 puts score = 0 # 不能有负分 end

使用 unless 和 if 的条件提示

user_count = 7

puts "Warning: limit exceeded" unless user_count < 10 puts "Warning: close to limit" if user_count <= 10

if-else 条件判断

if true puts "OK" else puts "Never reach here" end

a = 10 b = 20

if a > b puts "a is bigger" elsif a < b puts "b is bigger" else puts "a,b the same" end

使用 case 进行多条件判断

score = 70

result = case score when 0..60 "Fail" when 61..70 "Pass" when 71..95 "Pass with Distinction" when 96, 97, 98, 99 "Distinction" when 100 "High Distinction"
else "Invalid Score" end puts result # => Pass

while 循环

count = 0 while count < 10 count = count + 1 print count, " " end

1 2 3 4 5 6 7 8 9 10

for 循环

for i in 1..9 print i, " " end

1 2 3 4 5 6 7 8 9

until 循环

count = 1 until count >= 5 print count, " " count +=1 end

1 2 3 4

重复执行三次计算

number = 2 3.times do number = number * number end

3 次计算：2 * 2, 4 * 4, 16 * 16

puts number # => 256

遍历数字并跳过奇数

(1..5).each do |num| puts "Checking #{num} ..." next if num % 2 != 0 # 跳过奇数 puts "#{num} is an even number." end

使用 break 退出 while 循环

在 Ruby 中定义无限循环

while true

里面的代码会不断重复执行

必须添加退出条件

end

乘法表

for i in 1..9 do for j in 1..9 do puts "#{i} x #{j} = #{i * j}" end end

数组操作

score_list = [20, 10, 30, 50] puts score_list.inspect # => [20, 10, 30, 50] puts score_list.size # => 4 p score_list.reverse # => [50, 30, 10, 20] p score_list.sort # => [10, 20, 30, 50]，原数组未改变 p score_list # => [20, 10, 30, 50] p score_list.sort! # 修改原数组 p score_list # => [10, 20, 30, 50]

数组索引与查找

most_spoken_langs = ["Chinese", "Spanish", "English", "Hindi", "Arabic"] puts most_spoken_langs[0] # => "Chinese"，索引从 0 开始 puts most_spoken_langs[2] # => "English" puts most_spoken_langs[-1] # => "Arabic"，最后一个元素 puts most_spoken_langs[-2] # => "Hindi" puts most_spoken_langs.include?("Spanish") # => true puts most_spoken_langs.include?("Italian") # => false

修改数组

score_list = [20, 10, 30, 50] score_list.delete(30) # score_list 变为 [20, 10, 50] score_list << 90 score_list << 80 print score_list # => [20, 10, 50, 90, 80]

遍历数组并输出平方值

[20, 10, 30].each do |elem| puts "Square of #{elem} is #{elem * elem}" end

哈希操作

us_states = {"CA" => "California", "NY" => "New York", "TX" => "Texas"} us_states["FL"] = "Florida" us_states.size # => 4 us_states.delete("NY") puts us_states.inspect

遍历哈希并输出键值对

us_states = {"CA" => "California", "NY" => "New York", "TX" => "Texas"}

us_states.each { |key, value| puts "#{value}'s abbreviation is " + key }

定义函数

def square(num) num * num # => 等同于 return num * num end

puts square(2) # => 4 puts square(9) # => 81

带默认参数的函数

def exponentiate(num, power = 2) # power 的默认值为 2 num ** power # 指数运算 end

puts exponentiate(5) # => 25 puts exponentiate(5, 3) # => 125

变量作用域示例

@c = 1 # @实例变量，作用域为文件级别

def add(a, b) c = a + b # 函数内部局部变量 @c = c # 设置实例变量的值 puts "inside c = #{c}" end

c = 100 # 外部局部变量，与 add() 中的 c 不同 add(1, 2) add(2,3)

puts "Value of c declared outside the method = #{c}" puts "Value of @c set inside the method = #{@c}"