associations

来源： https://stackoverflow.com/questions/64104174/associations-not-working-with-test-entries

来源： https://stackoverflow.com/questions/9648927/uml-association-class-clarifying

来源： https://stackoverflow.com/questions/23122469/how-do-i-pass-an-argument-to-a-has-many-association-scope-in-rails-4

来源： https://stackoverflow.com/questions/23122469/how-do-i-pass-an-argument-to-a-has-many-association-scope-in-rails-4

来源： https://stackoverflow.com/questions/25966212/semantic-relationship-in-uml

问题 In short I would like to model a covariant association between two classes, that can each be specialized. I need to show the specialization of the related association-classes. But I want to avoid that my model could mean that there are redundant associations (i.e. one between the generalizations and one between the specializations. Step by step explanation of the problem I have in an UML class diagram a many-many association between a Person and a Contract . A person can be involved in

问题 I have an association m:n between two tables with sequelize like this: Course module.exports = function(sequelize, DataTypes) { var Course = sequelize.define('Course', { ..... }, { associate: function(models){ Course.hasMany(models.Schedule); Course.belongsTo(models.Period); Course.belongsTo(models.Room); Course.belongsTo(models.Subject); Course.belongsTo(models.School); Course.belongsTo(models.Person, { as: 'Teacher' }); } } ); return Course; }; Person module.exports = function(sequelize,

问题 I would really appreciate some help on this. I have relationships such as: class User < ActiveRecord::Base has_many :ideas, :class_name => 'Challenge', :foreign_key => 'creator_id' has_many :contributions, :class_name => 'Challenge', :foreign_key => 'contributor_id' class Challenge < ActiveRecord::Base belongs_to :creator, :class_name => 'User' belongs_to :contributor, :class_name => 'User' My problem is being able to display the name rather than the id of a user in the views for the

问题 I am trying to tidy the following dataset (in link) in R and then run an association rules below. https://www.kaggle.com/fanatiks/shopping-cart install.packages("dplyr") library(dplyr) df <- read.csv("Groceries (2).csv", header = F, stringsAsFactors = F, na.strings=c(""," ","NA")) install.packages("stringr") library(stringr) temp1<- (str_extract(df$V1, "[a-z]+")) temp2<- (str_extract(df$V1, "[^a-z]+")) df<- cbind(temp1,df) df[2] <- NULL df[35] <- NULL View(df) summary(df) str(df) trans <- as

问题 Hi, I have recently started to learn system analysis and design and am having some trouble understanding domain model class diagram (DMCD) association class. As per image, when drawing the DMCD, I'd like to understand if an association class is allowed to contain attributes of the classes it derives from. The Invoice needs to contain the attributes apptNo and svcName. Association class inquiry image: Do I include the attributes as shown in the image? Or do I assume that the Invoice would