在Ruby中动态创建多维哈希 [英] Dynamically creating a multi-dimensional hash in Ruby

问题描述

我是一名试图掌握Ruby技能的PHP开发人员。我现在正在削减我的一个项目是一个源代码审计工具，它可以扫描webapp文件，查找几种网络编程语言中潜在的危险功能。当找到匹配项时，脚本会将相关信息保存在 poi （兴趣点）类中以供稍后显示。

该类的示例实例看起来像这样（在YAML中建模）：

pre $ $ $ $ $ $ $ $ $ b file_type：php
file：the-scanned-file.php
line_number：100
match：eval（）
snippet：echo eval ）

在展示中，我想组织这些兴趣点如下所示：

   -  file_type 
  - 文件
 ---匹配（搜索到的有效内容）
  poi 对象成一个哈希镜像上面的结构。这将允许我简单地遍历散列中的项目以产生期望的屏幕上组织。 （或者至少，这是计划。）
 
 
 
现在，对于我的问题：我该如何在Ruby中执行此操作？
 
 
 
在PHP中，我可以很轻松地做这样的事情： 
 $ b 
 < ？php 
 
 $ sorted_pois = array（）; 
 foreach（$ points_of_interest as $ point）{
 $ sorted_pois [$ point-> file_type] [$ point-> file] [$ point-> match] [] = $ point; 
} 
 
？> 
  
我尝试将这种想法从PHP转换为Ruby，但是无济于事：
  sorted_pois = {} 
 @ points_of_interest.each_with_index do | point，index | 
 sorted_pois [point.file_type.to_sym] [point.file.to_sym] [point.match.to_sym] .push point 
 end 
  
我已经在这上面花了几个小时了，在这一点上我的头撞到了墙上，所以大概我是离开了基地。在Ruby中处理这个问题的正确方法是什么？
 
 
 
 更新：  
 $ b  
引用，这是我定义的精确方法：
 
 $ pre $ ＃将感兴趣的点排序为结构化散列
 def sort 
 sorted_pois = {} 
 @ points_of_interest.each_with_index do | point，index | 
 sorted_pois [point.file_type.to_sym] [point.file.to_sym] [point.match.to_sym] .push point 
 end 
 end 
  
 
 
 
这是我运行代码时收到的错误： 
 
 
  ./ lib / models / vulnscanner.rb：63：在`sort'中：未定义的方法`[]'为nil：NilClass（NoMethodError）
 from /usr/lib/ruby/1.8/rubygems/ custom_require.rb：31：在`each_with_index'
 from ./lib/models/vulnscanner.rb:62:in`each'
 from ./lib/models/vulnscanner.rb:62:in` each_with_index'
 from ./lib/models/vulnscanner.rb:62:in`sort'
 from ./webapp-vulnscan:69 
  
 
第62行（正如你可能推断的）特别是这一行：
 
 
  @points_of_interest.each_with_index do | point，index | 
  
作为附加参考，以下是 @points_of_interest 看起来像转换为YAML时：
   - ！ruby / object：PoI 
 file： models / couponkimoffer.php 
 file_type：php 
 group：：dangerous_functions 
 line_number：472
 match：`
 snippet：ORDER BY`created_at` DESC 
  - ！ruby / object：PoI 
 file：models / couponkimoffer.php 
 file_type：php 
 group：：dangerous_functions 
 line_number：818
 match： `
 snippet：WHERE`company_slug` ='$ company_slug'
  - ！ruby / object：PoI 
 file：models / couponkimoffer.php 
 file_type：php 
 group ：：dangerous_functions 
 line_number：819
 match：`
 snippet：ORDER BY`created_at` DESC 
  
 
 
解决方案 
 @ John's  Enumerable＃group_by 建议是解决您的需求的好方法。另一种方法是创建一个自动生成哈希（就像你看起来在PHP中一样）：
 $ b 
  hash = Hash。新{| h，k | h [k] = Hash.new（& h.default_proc）} 
 hash [：a] [：b] [：c] = 42 
 $ hash 
＃=> {：a => {：b => {：c => 42}}} 
  
请注意，如果您访问不存在的按键，这种自动生成功能可能会危险，因为它会为您创建它们： 
 
 
  p hash [这是否存在？] 
＃=> {} 
 
 p hash 
＃=> {：a => {：b => {：c => 42}}，这是否存在？=> {}} 
  
如果您使用键，您仍然可以使用生动的 default_proc  code>首先测试键：
 
 
  val = hash [OH NOES] if hash.key？ （OH NOES）
＃=>无
 
 p散列
＃=> {：a => {：b => {：c => 42}}，这是否存在？=> {}} 
  
 
 
 
 
 
 
 FWIW，你得到的错误说，嘿，你把 [] 之后，评估为 nil 和 nil 没有<$ c $ 
  sorted_pois   [point.file_type.to_sym] 
  
评估为零（因为哈希值没有这个键的值），然后你试图请求
 
 $ pre code> nil [point .file.to_sym] 
  

I'm a PHP developer who's trying to gain some proficiency in Ruby. One of the projects I'm cutting my teeth on now is a source-code auditing tool that scans webapp files for potentially dangerous functions in several web programming languages. When matches are found, the script saves the relevant information in a poi (point-of-interest) class for display later on.

An example instance of that class would look something like this (modeled in YAML):

poi:
    file_type: "php"
    file: "the-scanned-file.php"
    line_number: 100
    match: "eval()"
    snippet: "echo eval()"

On display, I want to organize these points of interest like so:

- file_type
-- file
--- match (the searched payload)

Thus, before presentation, I'm trying to structure a flat array of poi objects into a hash mirroring the structure above. This will allow me to simply iterate over the items in the hash to produce the desired on-screen organization. (Or at least, that's the plan.)

And now, for my question: how do I do that in Ruby?

In PHP, I could do something like this really easily:

<?php

$sorted_pois = array();
foreach($points_of_interest as $point){
    $sorted_pois[$point->file_type][$point->file][$point->match][] = $point;
}

?>

I've tried translating that thought from PHP to Ruby like this, but to no avail:

sorted_pois = {}
@points_of_interest.each_with_index do |point, index|
    sorted_pois[point.file_type.to_sym][point.file.to_sym][point.match.to_sym].push point
end

I've spent a few hours on this, and I'm kind of banging my head against the wall at this point, so presumably I'm way off-base. What's the proper way to handle this in Ruby?

Update:

For reference, this is the precise method I have defined:

# sort the points of interest into a structured hash
def sort
  sorted_pois = {}
  @points_of_interest.each_with_index do |point, index|
    sorted_pois[point.file_type.to_sym][point.file.to_sym][point.match.to_sym].push point
  end
end

This is the error I receive when I run the code:

./lib/models/vulnscanner.rb:63:in `sort': undefined method `[]' for nil:NilClass (NoMethodError)
    from /usr/lib/ruby/1.8/rubygems/custom_require.rb:31:in `each_with_index'
    from ./lib/models/vulnscanner.rb:62:in `each'
    from ./lib/models/vulnscanner.rb:62:in `each_with_index'
    from ./lib/models/vulnscanner.rb:62:in `sort'
    from ./webapp-vulnscan:69

Line 62 (as you can likely infer) is this line in particular:

@points_of_interest.each_with_index do |point, index|

As an additional reference, here's what (a snippet of) @points_of_interest looks like when converted to YAML:

- !ruby/object:PoI 
  file: models/couponkimoffer.php
  file_type: php
  group: :dangerous_functions
  line_number: "472"
  match: `
  snippet: ORDER BY `created_at` DESC
- !ruby/object:PoI 
  file: models/couponkimoffer.php
  file_type: php
  group: :dangerous_functions
  line_number: "818"
  match: `
  snippet: WHERE `company_slug` = '$company_slug'
- !ruby/object:PoI 
  file: models/couponkimoffer.php
  file_type: php
  group: :dangerous_functions
  line_number: "819"
  match: `
  snippet: ORDER BY `created_at` DESC

解决方案

@John's Enumerable#group_by suggestion is one good way to solve your needs. Another would be to create an auto-vivifying Hash (like you appear to have in PHP) like so:

hash = Hash.new{ |h,k| h[k] = Hash.new(&h.default_proc) }
hash[:a][:b][:c] = 42
p hash
#=> {:a=>{:b=>{:c=>42}}}

Note that this sort of auto-vivification can be 'dangerous' if you access keys that don't exist, as it creates them for you:

p hash["does this exist?"]
#=> {}

p hash
#=> {:a=>{:b=>{:c=>42}}, "does this exist?"=>{}}

You can still use the vivifying default_proc without hitting this danger if you use key? to test for the key first:

val = hash["OH NOES"] if hash.key?("OH NOES")
#=> nil

p hash
#=> {:a=>{:b=>{:c=>42}}, "does this exist?"=>{}}

---

FWIW, the error you are getting says, "Hey, you put [] after something that evaluated to nil, and nil doesn't have a [] method." Specifically, your code...

sorted_pois[point.file_type.to_sym]

evaluated to nil (because the hash did not yet have a value for this key) and then you attempted to ask for

nil[point.file.to_sym]

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