relationship

问题 I currently have a one to one relationship between two tables in MS Access like so: Student Results StudentResultsID (primary key, autonumber) Various fields relating to the course. AVETMISS Data StudentResultsID (primary key, long integer) Various fields relating to a specific, paper form that must be filled out by the student for each enrolment. When the user adds a new record to Student Results (this occurs everytime a student is enrolled into a course) I want to create a matching record

问题 In my Grails project I need to have a 1:N relationship between two domain classes. So, I've created the following domain class: class Receipt_HealthService { Receipt receipt HealthService healthService int quantity = 1 static constraints = { } } and in Receipt I have the following: @NotNull static hasMany = [healthServices:Receipt_HealthService] So a new table is created that has got the id of both domain class and the quantity field. When I call the save() method everything works well, but

问题 I have two Core Data entities: Parent and Child . Parent has to-many relationship to a Child called children . Inverse relationship from is Child.parent . So parent has CoreDataGeneratedAccessors : - (void)addChildrenObject:(Child *)value; and - (void)addChildren:(NSSet *)value; . Problem: after I add Child(s) by using one of those accessors and save managedObjectContext parent.children is empty. At the same time parent property of every added Child point to proper instance of Parent and

问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: MetaSearch “undefined method `model_name' for NilClass:Class” for global bar search This is the error I'm getting using my updated code when I try going to a user's profile or a individual posts (/posts/1). Its weird that its trying to access the unlike partial anyway because its a new user without any likes. I've got the code exactly as it shows in the tutorial I used to do this with following users. It works

问题 I have 5 models with one pivot table Country Province City Area Tour tour_location . How to achieve below functionality? $country->tours $province->tours $city->tours $area->tours Country.php HasMany Provinces public function provinces() { return $this->hasMany('App\Province', 'country_id', 'id'); } Province.php HasMany Cities public function cities() { return $this->hasMany('App\City', 'province_id', 'id'); } City.php HasMany Areas public function areas() { return $this->hasMany('App\Area',

问题 How do I represent a parent/child relationship on the same model? An example of this is a model representing a folder. A parent folder can have many children folders. But a child folder can only have one parent folder. Ember.js has the concept of reflexive relations. I would like to implement the first option. "... explicitly define the other side, and set the explicit inverse accordingly ..." How would I go about setting that up on the sails.js side of the SANE stack? 回答1: I'm not sure what

问题 I've been trying to learn OOP for the last few weeks as much as I can, and I've learned alot, but I'm not certain of this one, what should my class hierarchy look like? Imagine two classes, here's a Level -class: class Level(object): def __init__(self, level, exp): self.level = level self.exp = exp @property def required_exp(self, level=None): return 80 + 40 * (level or self.level) def add_exp(self, exp): self.exp += exp while self.exp >= self.required_exp: self.exp -= self.required_exp self

问题 I've been trying to learn OOP for the last few weeks as much as I can, and I've learned alot, but I'm not certain of this one, what should my class hierarchy look like? Imagine two classes, here's a Level -class: class Level(object): def __init__(self, level, exp): self.level = level self.exp = exp @property def required_exp(self, level=None): return 80 + 40 * (level or self.level) def add_exp(self, exp): self.exp += exp while self.exp >= self.required_exp: self.exp -= self.required_exp self

问题 I was able to do a specific pattern match from this original question Neo4j gem - Preferred method to deal with admin relationship via this Event.query_as(:event).match("(event)<-[invite:invited]-(user1:User)<-[friends_with:friends_with]-(user2:User)").where('invite.admin = true').pluck(:event) I was unable to get a modified version such as this to work current_user.friends.events.query_as(:event).match("(event)<-[invite:invited]-(user:User)").where(invite: {admin: true}).pluck(:event) So

问题 I was able to do a specific pattern match from this original question Neo4j gem - Preferred method to deal with admin relationship via this Event.query_as(:event).match("(event)<-[invite:invited]-(user1:User)<-[friends_with:friends_with]-(user2:User)").where('invite.admin = true').pluck(:event) I was unable to get a modified version such as this to work current_user.friends.events.query_as(:event).match("(event)<-[invite:invited]-(user:User)").where(invite: {admin: true}).pluck(:event) So