ruby on rails - How do I create a self join item when it also belongs to another model? -

i’m trying make self join relation model named: subsystem. in case subsystem represents java package, class or method. i’ve read rails documentation saw use this:

class subsystem < activerecord::base   has_many :child_subsystems, class_name: "subsystem",                           foreign_key: "parent_id"    belongs_to :parent, class_name: "subsystem" end 

i looked @ couple examples in cases “create part” not described. problem i’m looking best way create subsystems, because: subsystem model belongs project. right create subsystems like:

project.subsystems.create(params) 

i hope image make’s better understand. project, can have 0 multpiple subsystems, , every subsystem can have 0 multiple subsystems.

subsystems

i’ve seen examples of making self join, people created item relation build, i’m not sure how combine existing create: project.subsystems.create.

can me out? in advance!

the way created self join association spot on.

if want create subsystem belongs project can project.subsystems.create(...) , if want create subsystem belonging subsystem can subsystem.child_subsystems.create(..). call name of association defined in model (pluralised has many associations).

the difference between build , create methods build calls new whereas create calls new , save. when create or build instances associated other instances defined in models, returned objects contain foreign keys of records built or created from.