Question

我要向用户输入键currentline和值currentstation，以便将其与哈希进行比较，并显示要走的行。

mtahash = {
  n: ["timesq", "34thn", "28thn", "23rdn", "Union_Square", "8th"],
  l: ["8th", "6th", "Union_Square", "3rd", "1st"],
  s: ["Grand Central", "33rds", "28th", "23rds", "Union Square", "Astor Place"]
}

puts "Please enter your current station"
current_station = gets.chomp
puts "Please enter your current line"
current_line = gets.chomp

mtahash.each do |key, value|
  if key == current_line && value == current_station
    puts "got it"
  else
    puts "fish"
  end
end

无论输入什么，我的代码都会输出fish三次。

Answer 1

此迭代中的value是一个数组。您应该检查它是否包含站名，而不是是否相等。还可以使用key.to_s将键转换为字符串（现在是符号）：

 mtahash.each do |key, value|
   if key.to_s == current_line && value.include?(current_station)
     puts "got it"
   else
     puts "fish"
   end
 end

Answer 2

each将为每个键值进行迭代（即使找到一个匹配项），但是detect将在找到匹配项后停止。

我认为哈希键是唯一的，因此detect比使用each更好

mtahash.detect { |k, v| k.to_s == current_line && v.include?(current_station) } ? 'got it' : 'fish'

减少迭代次数。

 > mtahash = {:n=>["timesq", "34thn", "28thn", "23rdn", "Union_Square", "8th"], :l=>["8th", "6th", "Union_Square", "3rd", "1st"], :s=>["Grand Central", "33rds", "28th", "23rds", "Union Square", "Astor Place"]} 
 >   current_line, current_station = 'l', '3rd'
 => ["l", "3rd"] 

 > mtahash.detect { |k, v| k.to_s == current_line && v.include?(current_station) } ? 'got it' : 'fish'
 => "got it" 

 > current_line, current_station = 'l', '43rd'
 => ["l", "43rd"] 

 > mtahash.detect { |k, v| k.to_s == current_line && v.include?(current_station) } ? 'got it' : 'fish'
 => "fish"

Answer 3

我建议将用户输入的CREATE DEFINER=`root`@`localhost` FUNCTION `REMOVE_DUPLICATE_CHAR_FROM_STRING`(myString VARCHAR(50)) RETURNS varchar(50) CHARSET utf8mb4 COLLATE utf8mb4_general_ci NO SQL BEGIN DECLARE tempString VARCHAR(50) DEFAULT ''; DECLARE sPreviousChar VARCHAR(1); DECLARE sCurrentChar VARCHAR(1); DECLARE inti INTEGER DEFAULT 1; set tempString = myString; IF LENGTH(tempString) > 0 THEN WHILE(inti <= LENGTH(tempString)) DO SET sCurrentChar = SUBSTRING(tempString, inti, 1); IF inti > 1 THEN SET sPreviousChar = SUBSTRING(tempString, inti - 1, 1); IF sCurrentChar = sPreviousChar THEN SET tempString = CONCAT(LEFT(tempString, inti - 1), SUBSTRING(tempString, inti, 1000)); END IF; END IF; SET inti = inti + 1; END WHILE; RETURN (tempString); ELSE RETURN 0; END IF; END（String#to_sym）转换为current_line，因为哈希键是符号。

然后检查哈希是否具有该键（Hash#has_key）。

最后通过键访问哈希，并检查数组是否包含to_sym（Array#include），因为哈希值是数组。

这只是一个示例。

current_station

更好的是，反转输入顺序，在用户进入线路后检查

current_station = "timesq" # gets.chomp
current_line = "n".to_sym  # gets.chomp.to_sym <--- note .to_sym

if mtahash.has_key? current_line
    if mtahash[current_line].include? current_station
      then puts "got it"
      else puts "fish"
    end
  else puts "no line"
end

，如果为true，则去询问电台。

遍历以数组为值的哈希

3 个答案: