尝试向数组添加任何内容时，不会将nil隐式转换为整数 [英] no implicit conversion from nil to integer - when trying to add anything to array

问题描述

 没有从nil到隐式转换的结果
我试图构建一个相当复杂的散列，我很奇怪地得到错误整数
  

当我使用该行时

  manufacturer_cols<< {：field => 'test'} 
  

稍后在同一个循环中使用同一行，并且它没有任何问题。

整个代码是

$ p $ manufacturer_cols = []
manufacturer_fields.each_with_index do | mapped_field，index |


如果mapped_field.base_field_name =='exactSKU'

＃这是它破坏的地方，如果我评论这一点，一切都很好
manufacturer_cols<< {：base_field => 'test'}


else


＃在这里可以正常工作！
manufacturer_cols<< {：base_field => mapped_field.base_field_name}
结束
结束


- ------ manufacturer_fields的值--------

[{base_field：{base_field_name：Category，id ：1， 名称： 类别}}，{ base_field：{ base_field_name： 描述， ID：3 名称： SHORT_DESCRIPTION}}，{ base_field：{ base_field_name ： exactSKU， ID：5 名称： Item_SKU}}，{ base_field：{ base_field_name： 标记， ID：25， 姓名： Retail_Price }}，{base_field：{base_field_name：Family，id：26，name：Theme}}]

解决方案

隐式转换错误解释

我不确定您的代码为什么会出现此错误，但我可以准确地告诉您错误的含义，也许这将有所帮助。

Ruby中有两种转换类型： explicit 和隐式。 / p>

显式转换使用短名称，如 #to_s 或 #to_i。这些a通常在核心中定义，并且它们始终被调用。它们用于不是字符串或不是整数的对象，但可以转换为调试或数据库转换或字符串插值或任何其他类型。

隐式转换使用长名称 #to_str 或 #to_int。这种转换适用于非常像字符串或整数的对象，只需要知道什么时候采取他们的自我形式。这些转换从未或几乎从未在核心中定义。 （Hal Fulton的 Way 标识了 ）作为找到定义 #to_str 的原因的类之一。

很难得到你的错误，甚至 NilClass 定义了显式（短名称）转换器：

  nil.to_i 
 => 0 
 
>>＃{nil}<< ＃这演示了nil.to_s 
 => >><< 
  

您可以像这样触发它：

 Array.new nil 
 TypeError：不存在从nil到整数的隐式转换
  

因此，您的错误来自Ruby解释器中的C代码。在C语言中实现的核心类当它需要一个整数时，会被交给一个 nil 。它可能有一个 #to_i 但它没有 #to_int ，所以结果是 TypeError。

I'm trying to build a fairly complex hash and I am strangely getting the error

no implicit conversion from nil to integer

when I use the line

manufacturer_cols << {:field => 'test'}

I use the same line later in the same loop, and it works no problem.

The entire code is

manufacturer_cols=[]
manufacturer_fields.each_with_index do |mapped_field, index|


        if mapped_field.base_field_name=='exactSKU'

            #this is where it is breaking, if I comment this out, all is good
            manufacturer_cols << { :base_field=> 'test'}


    else


        #it works fine here!
        manufacturer_cols << { :base_field=>mapped_field.base_field_name }
    end
end

------- value of manufacturer_fields --------

[{"base_field":{"base_field_name":"Category","id":1,"name":"Category"}},{"base_field":{"base_field_name":"Description","id":3,"name":"Short_Description"}},{"base_field":{"base_field_name":"exactSKU","id":5,"name":"Item_SKU"}},{"base_field":{"base_field_name":"Markup","id":25,"name":"Retail_Price"}},{"base_field":{"base_field_name":"Family","id":26,"name":"Theme"}}]

解决方案

Implicit Conversion Errors Explained

I'm not sure precisely why your code is getting this error but I can tell you exactly what the error means, and perhaps that will help.

There are two kinds of conversions in Ruby: explicit and implicit.

Explicit conversions use the short name, like #to_s or #to_i. These are commonly defined in the core, and they are called all the time. They are for objects that are not strings or not integers, but can be converted for debugging or database translation or string interpolation or whatever.

Implicit conversions use the long name, like #to_str or #to_int. This kind of conversion is for objects that are very much like strings or integers and merely need to know when to assume the form of their alter egos. These conversions are never or almost never defined in the core. (Hal Fulton's The Ruby Way identifies Pathname as one of the classes that finds a reason to define #to_str.)

It's quite difficult to get your error, even NilClass defines explicit (short name) converters:

nil.to_i
=> 0

">>#{nil}<<" # this demonstrates nil.to_s
=> ">><<"

You can trigger it like so:

Array.new nil
TypeError: no implicit conversion from nil to integer

Therefore, your error is coming from the C code inside the Ruby interpreter. A core class, implemented in C, is being handed a nil when it expects an Integer. It may have a #to_i but it doesn't have a #to_int and so the result is the TypeError.

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