如何修复红宝石中的'This loop will have at most one iteration'

Question

我得到This loop will have at most one iteration以下代码块。但是当我添加else条件时，我得到了一个错误

def self.list_all_rentals_person_id(people, rentals)
list_all_people(people)
print 'ID of person: '
person_id = gets.chomp
rentals.each do |rental|
return puts "Rentals:nDate: #{rental.date}  Book: #{rental.book.title}" if rental.person.id == person_id
else
return puts 'No Rental Records Found'
end
end

但是当我只使用if和return时，if条件返回。我不会得到任何错误

def self.list_all_rentals_person_id(people, rentals)
list_all_people(people)
print 'ID of person: '
person_id = gets.chomp
rentals.each do |rental|
return puts "Rentals:nDate: #{rental.date}  Book: #{rental.book.title}" if rental.person.id == person_id
end
end

Answer 1

已经提供了您所做的错误的解释。

然而，你似乎真的想要Enumerable#find。

irb(main):001:0> a = [[4, 5], [2, 9], [7, 6]]
irb(main):002:1* if b = a.find { |x| x[0] > 6 }
irb(main):003:1*   p b
irb(main):004:1* else
irb(main):005:1*   puts "Nothing found"
irb(main):006:0> end
[7, 6]
=> [7, 6]

将此翻译为您的案例:

def self.list_all_rentals_person_id(people, rentals)
list_all_people(people)
print 'ID of person: '
person_id = gets.chomp
if rental = rentals.find { |rental| rental.person.id == person_id }
puts "Rentals:nDate: #{rental.date}  Book: #{rental.book.title}"
else
puts 'No Rental Records Found'
end
end

或者您可能想要使用Enumerable#select来获得所有符合您的标准的租赁。

def self.list_all_rentals_person_id(people, rentals)
list_all_people(people)
print 'ID of person: '
person_id = gets.chomp
matching_rentals = rentals.select { |r| r.person.id == person_id }
if matching_rentals.empty?
puts 'No Rental Records Found'
else
puts "Rentals:"
matching_rentals.each do |rental|
puts "Date: #{rental.date}  Book: #{rental.book.title}"
end
end
end

Answer 2

看看你的代码，你有很多小错误。

首先，Rubocop在循环的第一次迭代时直接报错，因为return将结束循环。如果在循环后移动返回值，它将循环直到找到第一个结果。

def self.list_all_rentals_person_id(people, rentals)
list_all_people(people)
print 'ID of person: '
person_id = gets.chomp
rentals.each do |rental|
return puts "Rentals:nDate: #{rental.date}  Book: #{rental.book.title}" if rental.person.id == person_id
end
puts 'No Rental Records Found'
end

(注意:如果你想在ruby中返回函数的最后一条语句，你可以去掉return，因为它总是返回值)

您的另一个问题是您不能将单行if语句return foo if bar与第二行else组合在一起。

return puts "Rentals:nDate: #{rental.date}  Book: #{rental.book.title}" if rental.person.id == person_id
else
return puts 'No Rental Records Found'
end

应该写成

if rental.person.id == person_id
return puts "Rentals:nDate: #{rental.date}  Book: #{rental.book.title}"
else
return puts 'No Rental Records Found'
end

但是，在这种情况下，Rubocop不会满意。