如何检查数组中是否存在空集? [英] How do I check if there's a nil set or not in an array?

问题描述

如果我为数组设置了一些nil值，我似乎无法检查它们.我已经尝试过any?和empty?.

If I set some nil values to an array, I don't seem to be able to check for them. I have tried any? and empty?.

array = [nil, nil, nil]
#=> [nil, nil, nil]

array[1].any?
#=> "NoMethodError: undefined method `any?' for nil:NilClass"

推荐答案

any?遍历容器(如数组)，并查看传递给它的每个元素以查看其是否通过测试.如果是，则循环停止并返回true:

any? iterates over a container, like an array, and looks at each element passed to it to see if it passes a test. If one does, the loop stops and true is returned:

ary = [nil, 1]

ary.any?{ |e| e.nil? } # => true

文档很好地解释了这一点:

The documentation explains this well:

将集合的每个元素传递到给定的块.如果该块曾经返回false或nil以外的值，则该方法返回true.如果未提供该块，则Ruby会添加一个{| obj |的隐式块obj}会导致什么?如果至少一个集合成员不是false或nil，则返回true.

Passes each element of the collection to the given block. The method returns true if the block ever returns a value other than false or nil. If the block is not given, Ruby adds an implicit block of { |obj| obj } that will cause any? to return true if at least one of the collection members is not false or nil.

%w[ant bear cat].any? { |word| word.length >= 3 } #=> true
%w[ant bear cat].any? { |word| word.length >= 4 } #=> true
[nil, true, 99].any?                              #=> true

any?是可用于数组以确定是否有

any? is one of a number of tests that can be applied to an array to determine if there are none?, any?, one?, or all?.

ary.one?{ |e| e == 1 } # => true
ary.none?{ |e| e == 2 } # => true
ary.all? { |e| e.nil? } # => false

您的代码失败，因为您尝试对nil值使用不存在的any?方法，因此出现错误:"NoMethodError:未定义的方法'any?'为nil:NilClass"

Your code fails because you're trying to use a non-existing any? method for a nil value, hence the error you got: "NoMethodError: undefined method `any?' for nil:NilClass"

ary[0] # => nil
ary.first # => nil
ary.first.respond_to?(:'any?') # => false

您必须注意自己在做什么. ary[0]或array.first返回该数组索引处的元素，而不是数组.

You have to pay attention to what you're doing. ary[0] or array.first returns the element at that array index, not an array.

empty? 仅检查容器中是否包含元素.换句话说，它的大小> 0吗?

empty? only checks to see if the container has elements in it. In other words, does it have a size > 0?

ary.empty? # => false
ary.size == 0 # => false
ary.size > 0 # => true
[].empty? # => true
[].size == 0 # => true
[].size > 0 # => false

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