Ruby：尝试在散列数组上获取枚举数时，未定义 nil:NilClass 的方法“[]”
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Ruby: undefined method `[]' for nil:NilClass when trying to get Enumerator on an Array of Hashes
提问by Joe Toug
I am trying to loop on an Array of Hashes. When I reach the point where I fetch the Enumerator to start looping, I get the following error:
我正在尝试循环哈希数组。当我到达获取 Enumerator 以开始循环的点时，出现以下错误：
undefined method `[]' for nil:NilClass
My code looks like the following:
我的代码如下所示：
def extraireAttributs (attributsParam)
classeTrouvee = false
scanTrouve = false
ownerOSTrouve = false
ownerAppTrouve = false
resultat = Hash.new(0)
attributs = Array(attributsParam)
attributs.each do |attribut| #CRASHES HERE!!!
typeAttribut = attribut['objectTypeAttribute']
[...]
I checked in debug mode to make sure the attributsParamsargument and the attributsvariable are not nil or empty. Both (because they are the same!) contain 59 Hashes objects, but I still cannot get an Enumerator on the Array.
我在调试模式下检查以确保attributsParams参数和attributs变量不为零或为空。两者（因为它们是相同的！）都包含 59 个 Hashes 对象，但我仍然无法在数组上获得枚举器。
Why do I keep on getting this error?
为什么我不断收到此错误？
Thanks!
谢谢！
回答by Schwern
undefined method `[]' for nil:NilClasssays you tried to do something[index]but somethingis nil. Ruby won't let you use nilas an array (ie. call the []method on it).
undefined method `[]' for nil:NilClass说你试图做something[index]但是something是nil。Ruby 不会让您nil用作数组（即调用[]它的方法）。
The problem is not on the attributs.eachline but on the line following which calls the []method on attribut.
问题不在attributs.each行上，而是在调用[]on 方法的行上attribut。
typeAttribut = attribut['objectTypeAttribute']
This indicates something in attributsis nil. This could happen if attributsParamis a list that contains nil like so.
这表明里面的东西attributs为零。如果attributsParam是一个包含 nil 的列表，则可能会发生这种情况。
attributsParam = [nil];
attributs = Array(attributsParam);
# [nil]
puts attributs.inspect
Simplest way to debug it is to add puts attributs.inspectjust before the loop.
调试它的最简单方法是puts attributs.inspect在循环之前添加。
Also consider if you really need the attributs = Array(attributsParam)line or if it's already something Enumerable.
还要考虑您是否真的需要该attributs = Array(attributsParam)行，或者它是否已经是Enumerable。
