如何模型许多家长很多自我指涉的关系？ [英] How to model a many self-referential relationship with many parents?

问题描述

我要模拟出最简单的方法如下：

I want to model out the following in the easiest way:

一个技能有很多相关的技能。

A skill has many dependent skills.

每个技能应该存在于自己的，和技能可能有其他的技能，prerequisite技能。

Each skill should exist on their own, and a skill may have other skills that are prerequisite skills.

例如：

Skill: Front-End Development Has Dependent Skills -> [HTML, CSS, SCSS]
Skill: Web-Design Has Dependent Skills -> [HTML, CSS]
Skill: HTML

我希望能够做到：

I'd like to be able to do:

@front_end_development.dependent_skills ##or a more semantic mapping

我可能会喜欢走了树，但我不认为这样做最好的名字。也许我想通过HTML引用一个网页设计依赖于它。

I'd probably like to walk up the tree but I can't think of the best name to do so. Perhaps I'd like to reference through HTML that Web-Design depends upon it.

是否有意义，使这个自我指涉或者是事实，这是伤害我的脑子code气味和求别的东西是理想的？这一切都归结到这取决于其他技能的技能。

Does it make sense to make this self-referential or is the fact that this is hurting my brain a code smell and beg that something else is ideal? It all comes down to a skill depending on other skills.

难道是更好地使用这种蒙戈模式？

Would it be better to model this using mongo?

推荐答案

而不是通过树遍历（更像是一个有向图实际上）每次需要检索所有依赖关系的技能的时候，你可能只是通过暗示迭代添加依赖性，当一个新的依赖于特定的技能和这些保存到一个名为'依赖'表，技能映射到一个依赖关系，反之亦然。例如（的关系，可以更好地措辞）：

Instead of iterating through the tree (more like a directed graph actually) each time you need to retrieve all dependencies for a skill, you might just iterate through the implied dependencies when adding a new dependency to a particular skill and save these to a table called 'Dependency' which maps a skill to a dependency and vice versa. For example (the relations could be better worded):

class Skill
    has_many :dependers, class_name: 'Dependency', foreign_key: :dependee_id
    has_many :dependees, class_name: 'Dependency', foreign_key: :depender_id

    has_many :dependencies, through: :dependees
    has_many :depending, through: :dependers

    def add_dependency(skill)
        recurse_dependencies(skill)
    end

    def recurse_dependencies(skill)
        # perform this check to avoid circular and duplicate dependencies
        if !depender_ids.include?(skill.id) && !dependee_ids.include?(skill.id)
            dependee_ids << skill.id
        end

        skill.dependencies.each do |dependency|
            recurse_dependencies(dependency)
        end
    end
end

class Dependency
    belongs_to :dependee
    belongs_to :depender
end

您应该然后就可以做这样的事情：

You should then be able to do things like:

@front_end_development.dependencies
@front_end_development.depending
@front_end_development.add_dependency(@html)

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