Ruby

Question

正在编写年龄检查程序，正在添加代码以检查输入错误。

我无法理解一段代码的问题所在，ruby returns a (NoMethodError) for .to_i 方法传递到一些字符串对象中。

完整代码如下；

def calculate_difference(year,month,day)
  years = Time.new.year - year
  months = Time.new.month - month
  days = Time.new.day - day 
  if months == 0
    if days < 0
        age = years - 1
    elsif days >= 0
        age = years
    end
  elsif months > 0
    age = years
  else
    age = years - 1
  end
end

puts "What year were you born in?"
year = gets.chomp
while year.to_i < 1900 or year.to_i > Time.new.year - 5
  puts "Please enter a year between 1900 and 5 years ago"
  year = gets.chomp
end
puts "And the month?"
month = gets.chomp
while month.to_i > 12 or month.to_i <= 0
  puts "MONTH please, numbers from 1 to 12..."
  month = gets.chomp
end
puts "And the day number?"
day = gets.chomp

#有问题的代码块：

if month.to_i = 1 or month.to_i = 3 or month.to_i = 5 or month.to_i = 7 or month.to_i = 8 or month.to_i = 10 or month.to_i = 12
  while day.to_i > 31 or day.to_i <= 0
  puts "Your month of birth has 31 days, please select a date within the correct range"
  day = gets.chomp
  end
end
if month.to_i = 2
  while day.to_i > 28 or day.to_i < 0
    puts "Incorrect day selected for February"
    day = gets.chomp
  end
end

 stringdate = year+month+day
    stringdate = stringdate.gsub(" ","")
    while stringdate.length != 8
        puts "in number format please: yyyy/mm/dd"
        puts "What year were you born in?"
        year = gets.chomp
        puts "And the month?"
        month = gets.chomp
        puts = "And the day number?"
        day = gets.chomp
    end
    year = year.to_i
    month = month.to_i
    day = day.to_i

    puts "Congratulations, you are #{calculate_difference(year,month,day)} years old."

我不确定为什么会返回错误，因为我确定字符串整数会响应 .to_i 方法。

Answer 1

"=" 是赋值。 “==”正在检查它们是否相等以及 returns 真或假。

if month.to_i == 1 or month.to_i == 3 or month.to_i == 5 or month.to_i == 7 or month.to_i == 8 or month.to_i == 10 or month.to_i == 12
  while day.to_i > 31 or day.to_i <= 0
  puts "Your month of birth has 31 days, please select a date within the correct range"
  day = gets.chomp
  end
end
if month.to_i == 2
  while day.to_i > 28 or day.to_i < 0
    puts "Incorrect day selected for February"
    day = gets.chomp
  end
end

或更具可读性：

if [1, 3, 5, 7, 8, 10, 12].include? month.to_i
  while day.to_i > 31 or day.to_i <= 0
    puts "Your month of birth has 31 days, please select a date within the correct range"
    day = gets.chomp
  end
end
if 2 == month.to_i
  while day.to_i > 28 or day.to_i < 0
    puts "Incorrect day selected for February"
    day = gets.chomp
  end
end

Answer 2

错误消息显示为 "undefined method 'to_i='" 而不是“to_i”

这是因为 Ruby 将单个“=”解释为好像您想在假设字段上调用 setter 方法 to_i:

a = "12"
a.to_i == 12
# returns true

a.to_i = 12
# throws undefined method to_i= 

12 = a.to_i
# creates a syntax error with the better message "unexpected ="
# prevents such assigns-equals errors
12 == a.to_i
# returns true

Ruby - 字符串 .to_i 错误

Ruby - String .to_i error

nomethoderror