如何为 nil:NilClass 捕获“未定义的方法‘[]’"错误? [英] How to catch an "undefined method `[]' for nil:NilClass" error?

问题描述

我通过 omniauth 从 facebook 获取了一个嵌套数组，想检查它是否为空?/nil?/exists?依赖线看起来像:

I get an nested array from facebook via omniauth and wanna check if it's empty?/nil?/exists? the depending line looks like:

 unless omniauth['extra']['raw_info']['location']['name'].nil?

这应该检查数组的这部分是否为空或存在.

This should check if this part of the array is empty or exists.

但总是抛出这个错误:

undefined method `[]' for nil:NilClass

我检查数组有错吗?

我用has_key"nil"试过了?空的?"存在吗?"空白?"

I tried it with "has_key" "nil?" "empty?" "exists?" "blank?"

但这些都没有用！

请帮助我，非常感谢！

推荐答案

聚会有点晚，但是，正如 this答案，Ruby 2.3.0 引入了一个新方法称为dig，如果链式键之一是nil，它将返回nil.您的 omniauth auth 哈希可以表示为:

A bit late to the party, but, as pointed in this answer, Ruby 2.3.0 introduced a new method called dig, which would return nil if one of the chained keys is nil. Your omniauth auth hash could then be presented as:

omniauth = { 
            ...                 
            "extra"=>{ "raw_info"=>
                        { "location"=>"New York",
                          "gravatar_id"=>"123456789"}}
             ...
           }


omniauth.dig('extra', 
             'raw_info',
             'location',
             'name',
             'foo',
             'bar',
             'baz') #<= nil

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