associations

问题 Apologies if this is a slightly noob question, but looking to clarify my thoughts on this. I have a model that can EITHER belong to one model, or another. For example: Let's say I have a Team model and I have a Member model, and both of those models can have one BankAccount. class Team has_many :members has_one :bank_account end class Member belongs_to :team has_one :bank_account end class BankAccount belongs_to :team, :member end To me, the above makes sense, but I'd love to clarify this

问题 Hi im making a small site to help me and friends learn languages. Typical use: Adam is english but is learning japanese. Adam can practice his japanese by writing and submitting articles written in japanese. Adam cant (not allowed to) submit any articles written in his native language. Adam can read articles (written in English) by other users who are learning English Im trying to think how to model this and its proving to be more difficult than the standard rails has many belongs to

问题 Association mining seems to give good results for retrieving related terms in text corpora. There are several works on this topic including well-known LSA method. The most straightforward way to mine associations is to build co-occurrence matrix of docs X terms and find terms that occur in the same documents most often. In my previous projects I implemented it directly in Lucene by iteration over TermDocs (I got it by calling IndexReader.termDocs(Term)). But I can't see anything similar in

问题 Association mining seems to give good results for retrieving related terms in text corpora. There are several works on this topic including well-known LSA method. The most straightforward way to mine associations is to build co-occurrence matrix of docs X terms and find terms that occur in the same documents most often. In my previous projects I implemented it directly in Lucene by iteration over TermDocs (I got it by calling IndexReader.termDocs(Term)). But I can't see anything similar in

问题 In my schema I have a model called Imprintables. In this model I have this self-referential relationship: class Imprintable < ActiveRecord::Base has_and_belongs_to_many :coordinates, class_name: 'Imprintable', association_foreign_key: 'coordinate_id', join_table: 'coordinates_imprintables' ... end In the imprintable create/edit form I have a select field where users can select coordinate imprintables (coordinates are used to identify imprintables that are similar to the one being created

问题 I've got the following entities on my EDMX :- These two entites were generated by Update Model From Database . Now, notice how my country has the following primary key :- Name & IsoCode this is because each country is UNIQUE in the system by Name and IsoCode. Now, with my States ... it's similar. Primary Key is :- Name & CountryId Each state is unique by name and per country. Now, the Foreign Key for States is a CountryId. This is the sql :- ALTER TABLE [dbo].[States] WITH CHECK ADD

问题 The Code (Rails 4.0.0) class Track < ActiveRecord::Base has_many :artist_tracks has_many :owning_artists, -> { where(:artist_tracks => { :artistic_role_id => 1 }) }, :through => :artist_tracks, :source => :artist end class ArtistTrack < ActiveRecord::Base belongs_to :artist belongs_to :track belongs_to :artistic_role end class Artist < ActiveRecord::Base has_many :artist_tracks has_many :tracks, :through => :artist_tracks end Finding Works # artist_tracks.artistic_role_id is properly set to

问题 I'm still not very clear about the way cascade works in deletion operations. I was wondering what happens if I have this: class myBean{ @ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL) public Cliente getClienteDiAppartenenza() { return clienteDiAppartenenza; } } class Cliente{ @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true, fetch = FetchType.LAZY) public List<myBean> getMyBeans() { return myBeans; } } if I delete the myBean with this property I'm not sure if the

问题 I'm having issues. I want to use the nice ExtJS associations, but they're not working properly. Issues: no association showing in the model no data showing up after load What are the quirks to watch out for? 回答1: I recently went through a very painful learning curve with the ExtJS associations, and came across some useful articles, as well as my own gotchas. Here is the summary for those who run into the same pains. Rules for HasMany Associations in ExtJS Always put your Proxies in your

问题 I've recently spent a good deal of time performing detailed UML designs of various SW components that I have since written. Looking back on what I have recently finished and comparing that to when I first learned UML, I see that I now almost strictly use Aggregation and Composition relationships, and have virtually abandoned "vanilla" non-directed/directed relationships. I still of course use Generalizations and Realizations, but these are distinctly different than those above and are not