Ruby異常初始化錯誤

Question

我必須創建一個程序，我必須在一行中詢問用戶的姓名。如果用戶只放置他們的第一個OR姓，它將通過該例外被拒絕。我在最後（如下）不斷收到錯誤。

class MyNewException < Exception 
     attr_accessor :first, :last 
     def initialize (first, last) 
     @first = first 
     @last = last 
     end 
    end 

print "Enter your first and last name:" 

begin 

first, last = gets.chomp.split 

print "Hello," + first + " " + last + "!" 

if last.size == 0 
    raise MyNewException, "Sorry, I didn't catch that! Try again:" 
end 
rescue MyNewException 
    puts "Sorry, I didn't catch that. Try again:" 
    retry 
end 

不斷收到一個錯誤：

testing.rb:15:in `+': no implicit conversion of nil into String (TypeError) 

Answer 1

的raise() docs有故障。你可以這樣做：

puts "Enter your first and last name:" 
name = gets.chomp 

class MyNewException < Exception 

    def initialize(str) 
    super(str) #pass the value for the message property to the parent class 
    end 

end 

begin 
    raise MyNewException, "Sorry, I didn't quite catch that! Try again:" 
rescue MyNewException => e 
    puts e.message 
end 

--output:-- 
Enter your first and last name: 
Sarah Kim 
Sorry, I didn't quite catch that! Try again: 

或者：

puts "Enter your first and last name:" 
name = gets.chomp 

class MyNewException < Exception 

    attr_accessor :first, :last 

    def initialize(user_name, exception_message) 
    @first, @last = user_name.split 
    super exception_message 
    end 

end 

begin 
    raise MyNewException.new(name, "I didn't quite catch that! Try again:") 
rescue MyNewException => e 
    puts e.message 
    puts e.first 
    puts e.last 
end 

--output:-- 
Enter your first and last name: 
Sarah Kim 
I didn't quite catch that! Try again: 
Sarah 
Kim 

下面是如何寫一個無限循環獲取用戶輸入：

class Person 
    attr_accessor :first, :last 

    def initialize(first, last) 
    @first = first.capitalize 
    @last = last.capitalize 
    end 
end 

while true 
    puts "Enter your first and last name:" 
    first, last = gets.chomp.split 
    #Show what you got: 
    p first 
    p last 

    if first and last 
    #If no names were entered, both first and last will be nil. 
    #If one name was entered, first will evaluate to true and last will be nil. 
    #If two names were entered, first and last will evaluate to true. 
    #If two or more names were entered, first and last will evaluate to true. 
    user = Person.new first, last 
    break #jump to the line immediately after the infinite loop 
    end 

    puts "Sorry, you must enter both a first and a last name. Try again" 
end 

puts "Thanks #{user.first} #{user.last}!" 

Answer 2

創建一個循環，做你的試驗和錯誤。 作爲我的回答，我選擇while循環

i = 0 
while i < 1 do 

    if condition == true 
     # display your greetings then increment loop to end 
     i += 1 
    else 
     # display error message 
    end 

end 

所以，你的代碼會是這樣

class MyNewException < Exception 

    attr_accessor :first, :last, :valid 

    def initialize(first, last) 
    @first = first 
    @last = last 
    @valid = true 
    if first.empty? || last.empty? then 
     @valid = false 
    end 
    end 

end 

i = 0 

while i < 1 do 

    print "Enter your first name: " 
    firstname = gets.chomp 
    print "Enter your last name: " 
    lastname = gets.chomp 

    name = MyNewException.new(firstname, lastname) 

    if name.valid then 
     puts "Greetings " << name.first << " " << name.last 
     i += 1 
    else 
     puts "I didn't quite catch that! Try again:" 
    end 

end