未定義的方法長度和下一個！對於零：NilClass

Question

我有這樣的代碼：

def encrypt(x) 
    index = 0 
    alphabet = "abcdefghijklmnopqrstuvwxyz" 
    while index < x.length 
    letter = x[index] 
    if letter == ' ' 
     print ' ' 
     index += 1 
    elsif letter == "z" 
     print "a" 
     index += 1 
    else 
     letter = alphabet[letter].next! 
     index += 1 
     print letter 
    end 
    end 
end 

def decrypt(x) 
    number = 0 
    alphabet = "abcdefghijklmnopqrstuvwxyz" 
    while number < x.length 
    green = x[number] 
    if green == ' ' 
     print ' ' 
     number += 1 
    else 
     red = alphabet.index(green) 
     red = red.to_i 
     blue = red - 1 
     yellow = alphabet[blue] 
     print yellow 
     number += 1 
    end 
    end 
end 

如果我添加一個大寫字母，如：

encrypt("Dhd d hd h") 

返回：

undefined method `next!' for nil:NilClass 
(repl):13:in `encrypt' 
(repl):39:in `initialize' 

，或者如果我嘗試使用兩種方法：

encrypt(decrypt("Dhddhdh")) 

返回

undefined method `length' for nil:NilClass 
(repl):4:in `encrypt' 
(repl):39:in `initialize' 

我認爲這是由於其在參數空間，並添加了對一個if/else，但沒有運氣。有人能指引我朝着正確的方向嗎？

Answer 1

在這兩種情況下，你alphabeth應包括小寫和downcase CARACTERES：

字母= 「abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ」

與您的代碼另一個問題是，不是打印的CARACTERES，我建議你返回一個值：

def encrypt(x) 
    index = 0 
    encrypted = "" 
    alphabet = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ" 
    while index < x.length 
    letter = x[index] 
    if letter == ' ' 
     encrypted << ' ' 
    elsif letter == "z" 
     encrypted << "a" 
    elsif letter == "Z" 
     encrypted << "A" 
    else 
     letter = alphabet[letter].next! 
     encrypted << letter 
    end 

    index += 1 
    end 

    encrypted 
end 

解密方法：

def decrypt(x) 
index = 0 
    decrypted = "" 
    alphabet = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ" 
    while index < x.length 
    letter = x[index] 
    if letter == ' ' 
     decrypted << ' ' 
    elsif letter == "A" 
     decrypted << "Z" 
    else 
     blue = alphabet.index(letter) - 1 
     decrypted << alphabet[blue] 
    end 

    index += 1 
    end 

    decrypted 
end