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• Are reads and (transactional) writes faster for entities of the same group than otherwise?

  - by indiehacker

  What advantage is there to designing child-parent relationships, which allow us to do writes in transactions, when there is never a real concern for consistency and contention and those sort of more complex issues? Does it make writes and reads faster? Consider my situation where there are many .png images that are referenced to one mosaic layer, and these .png images are written just once by a single user. The user can design many mosaic layers and her mosaic layers and referenced image entities are never changed/updated, they are just deleted some time in the future. Other users can come to the web project site and interactively view the mosaic layer as different layouts/configurations of the images as they play (query) with different criteria. So reads should be very fast. So there is no real worry of contention, or users conflicting with one another with writing new image entities. And because of that I am assuming there is no "requirement" for the .png image entities to be grouped by their same mosaic layer in child-parent relationship. However, perhaps, since the documentation says they are stored close to one another, if the many image entities were grouped as children to a single mosaic layer parent than this has the advantage that the writing (in transaction) and reading will happen much faster?

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• Representing versions of objects with CakePHP

  - by user636901

  Hi people, Have just started to get into CakePHP since a couple of weeks back. I have some experience with MVC-frameworks, but this problem holds me back a bit. I am currently working on a model foo, containing a primary id and some attributes. Since a complete history of the changes of foo is necessary, the content of foo is saved in the table foo_content. The two tables are connected through foo_content.foo_id = foo.id, in Cake with a foo hasMany foo_content-relationship. To track the versions of foo, foo_content also contains the column version, and foo itself the field currentVersion. The version is an number incremented by one everytime the user updates foo. This is an older native PHP-app btw, to be rewritten on top of Cake. 9 times out of 10 in the app, the most recent version (foo.currentVersion) is the db-entry that need to be represented in the frontend. My question is simply: is there someway of representing this directly in the model? Or does this kind of logic simply need to be defined in the controller? Most grateful for your help!

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• Core Data combined Query

  - by Chris Summer

  Hey, i have question related to CoreData. My iphone project has 2 Entities, Organisation and Brand with a 1 to many "BrandsToOrg" relationship and inverse. So my project has a Mapview, where you can see all the Organisations and a little subview when you click on those Organisations.At the subview there is a "show Brands" Button, which should init a new TableView who only shows the brands belong to the seleceted organisation. Any ideas how i can code that? thx NSPredicate *predicate = [NSPredicate predicateWithFormat: @"(TitleMedium == %@)",@"Rock Antenne"];???? NSFetchRequest *request = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:self.entityName inManagedObjectContext:managedObjectContext]; [request setEntity:entity]; // If a predicate was passed, pass it to the query if(predicate != nil) { [request setPredicate:predicate]; } // If a sort key was passed, use it for sorting. NSString *sortKey=@"TitleMedium"; BOOL sortAscending=YES; if(sortKey != nil) { NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:sortKey ascending:sortAscending]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; [request setSortDescriptors:sortDescriptors]; [sortDescriptors release]; [sortDescriptor release]; } NSError *error; NSMutableArray *mutableFetchResults = [[managedObjectContext executeFetchRequest:request error:&error] mutableCopy]; [request release]; [self setEntityArray:mutableFetchResults];

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• hibernate annotation bi-directional mapping

  - by smithystar

  I'm building a web application using Spring framework and Hibernate with annotation and get stuck with a simple mapping between two entities. I'm trying to create a many-to-many relationship between User and Course. I followed one of the Hibernate tutorials and my implementation is as follows: User class: @Entity @Table(name="USER") public class User { private Long id; private String email; private String password; private Set<Course> courses = new HashSet<Course>(0); @Id @GeneratedValue @Column(name="USER_ID") public Long getId() { return id; } public void setId(Long id) { this.id = id; } @Column(name="USER_EMAIL") public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } @Column(name="USER_PASSWORD") public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } @ManyToMany(cascade = CascadeType.ALL) @JoinTable(name = "USER_COURSE", joinColumns = { @JoinColumn(name = "USER_ID") }, inverseJoinColumns = { @JoinColumn(name = "COURSE_ID") }) public Set<Course> getCourses() { return courses; } public void setCourses(Set<Course> courses) { this.courses = courses; } } Course class: @Entity @Table(name="COURSE") public class Course { private Long id; private String name; @Id @GeneratedValue @Column(name="COURSE_ID") public Long getId() { return id; } public void setId(Long id) { this.id = id; } @Column(name="NAME") public String getName() { return name; } public void setName(String name) { this.name = name; } } The problem is that this implementation only allows me to go one way user.getCourses() What do I need to change, so I can go in both directions? user.getCourses() course.getUsers() Any help would be appreciated.

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• ASP.net MVC Linq-To-SQL Extended Class Field Binding

  - by user336858

  Hi there, The short version of this question is "Is there a way to get automatic View Object binding for fields defined in a partial class for a Linq-To-SQL generated class?" Apologies if it's been asked before. Example Suppose I have a typical MVC setup with the tables: Posts {PostID, ...} Categories {CategoryID, ...} A post can have more than one category, and a category can identify more than one post. Thus suppose further that I need an extra table: PostCategories {PostID, CategoryID, ...} This handles the many-to-many relationship between posts and categories. As far as I know, there's no way to do this in Linq-to-SQL right now so I have to shoehorn it in by adding a partial Postclass to the project to add that functionality. Something like: public partial class Post { public IEnumerable<Category> Categories{ get { ... } set { ... } } } So here's my question: If a user is accessing my MVC application front-end and begins editing a Post object, they might enter an invalid category. When the server recognizes the invalid input, the usual practice is to return the faulty object to the original view for re-editing along with some error messages. The fields in the edit page are re-populated with the provided values. However I don't know how to get this mechanism to work with the properties I created with the partial class as shown above. Any terminology, links, or tips you can provide would be tremendously helpful!

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• Doctrine YAML not generating correctly? Or is this markup wrong?

  - by ropstah

  I'm trying to get a many-to-many relationship between Users and Settings. The models seem to be generated correctly, however the following query fails: "User_Setting" with an alias of "us" in your query does not reference the parent component it is related to. $q = new Doctrine_RawSql(); $q->select('{s.*}, {us.*}') ->from('User u CROSS JOIN Setting s LEFT JOIN User_Setting us ON us.usr_auto_key = u.usr_auto_key AND us.set_auto_key = s.set_auto_key') ->addComponent('s', 'Setting s INDEXBY s.set_auto_key') ->addComponent('us', 'User_Setting us') ->where(u.usr_auto_key = ?',$this->usr_auto_key); $this->settings = $q->execute(); Does anyone spot a problem? This is my YAML: User: connection: default tableName: User columns: usr_auto_key: type: integer(4) fixed: false unsigned: false primary: true autoincrement: true notnull: true email: type: string(100) fixed: false unsigned: false primary: false default: '' notnull: true autoincrement: false password: type: string(32) fixed: false unsigned: false primary: false default: '' notnull: true autoincrement: false relations: Setting: class: Setting foreignAlias: User refClass: User_Setting local: usr_auto_key foreign: set_auto_key Setting: connection: default tableName: Setting columns: set_auto_key: type: integer(4) fixed: false unsigned: false primary: true autoincrement: true notnull: true name: type: string(50) fixed: false unsigned: false primary: false notnull: true autoincrement: false User_Setting: connection: default tableName: User_Setting columns: usr_auto_key: type: integer(4) fixed: false unsigned: false primary: true autoincrement: false notnull: true set_auto_key: type: integer(4) fixed: false unsigned: false primary: true autoincrement: false notnull: true value: type: string(255) fixed: false unsigned: false primary: false notnull: true autoincrement: false relations: Setting: foreignAlias: User_Setting local: set_auto_key foreign: set_auto_key User: foreignAlias: User_Setting local: usr_auto_key foreign: usr_auto_key

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• MySQL Join Question

  - by rbaker86

  Hi i'm struggling to write a particular MySQL Join Query. I have a table containing product data, each product can belong to multiple categories. This m:m relationship is satisfied using a link table. For this particular query I wish to retrieve all products belonging to a given category, but with each product record, I also want to return the other categories that product belongs to. Ideally I would like to achieve this using an Inner Join on the categories table, rather than performing an additional query for each product record, which would be quite inefficient. My simplifed schema is designed roughly as follows: products table: product_id, name, title, description, is_active, date_added, publish_date, etc.... categories table: category_id, name, title, description, etc... product_category table: product_id, category_id I have written the following query, which allows me to retrieve all the products belonging to the specified category_id. However, i'm really struggling to work out how to retrieve the other categories a product belongs to. SELECT p.product_id, p.name, p.title, p.description FROM prod_products AS p LEFT JOIN prod_product_category AS pc ON pc.product_id = p.product_id WHERE pc.category_id = $category_id AND UNIX_TIMESTAMP(p.publish_date) < UNIX_TIMESTAMP() AND p.is_active = 1 ORDER BY p.name ASC I'd be happy just retrieving the category id's releated to each returned product row, as I will have all category data stored in an object, and my application code can take care of the rest. Many thanks, Richard

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• Mongodb, linq driver. How to construct Contains with variable or statements

  - by Syska

  I'm using the LINQ Driver for C#, works great. Sorting a lot of properties but heres a problem I can't solve, its probebly simple. var identifierList = new []{"10", "20", "30"}; var newList = list.Where(x => identifierList.Contains(x.Identifier)); This is NOT supported ... So I could do something like: var newList = list.Where(x => x.Identifier == "10" || x.Identifier == "20" || x.Identifier == "30"); But since the list is variable ... how do I construct the above? Or are there even better alternatives? The list is of type IQueryable<MyCustomClass> For information ... this is used as a filter of alot of properties. In SQL I could have a parent - child relationship. But as I can't as the parent for the main ID I need to take all the ID's out and then construct it like this. Hopes this makes sense. If needed I will explain more.

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• C++ reinterpret cast ?

  - by Ian

  I would like to cast one object of the class PointsList to another object Points3DList (and vice versa) where: template <class T> class PointsList { protected: std::vector <Point <T> *> points; //Only illustration, not possible with templaes }; and template <class T> class Points3DList { protected: std::vector <Point3D<T> *> points; //Only illustration, not possible with templaes }; Between Point and Point3D there is no relationship (inheritance nor composition)... template <class T> class Point { protected: T x; T y; }; template <class T> class Point3D { protected: T x; T y; T z; }; What do you think about conversion Points3DList <T> *pl3D = new Points3DList <T> (); ... PointsList <T> *pl = reinterpret_cast < PointList <T> * > ( pl3D ); where pl3D represents pointer to Points3DList object.. Can reinterpret_cast be used in this case or it is better to create a conversion function? Data model in this case can not be changed...

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• IEnumerator seems to be effecting all objects, and not one at a time

  - by PFranchise

  Hey, I am trying to alter an attribute of an object. I am setting it to the value of that same attribute stored on another table. There is a one to many relationship between the two. The product end is the one and the versions is the many. Right now, both these methods that I have tried have set all the products returned equal to the final version object. So, in this case they are all the same. I am not sure where the issue lies. Here are my two code snipets, both yield the same result. int x = 1 IEnumerator<Product> ie = productQuery.GetEnumerator(); while (ie.MoveNext()) { ie.Current.RSTATE = ie.Current.Versions.First(o => o.VersionNumber == x).RSTATE; x++; } and foreach (var product in productQuery) { product.RSTATE = product.Versions.Single(o => o.VersionNumber == x).RSTATE; x++; } The versions table holds information for previous products, each is distinguished by the version number. I know that it will start at 1 and go until it reaches the current version, based on my query returning the proper number of products. Thanks for any advice.

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• How to select "child" entities in subview?

  - by Andy

  I am trying to manage a drill-down list of data. I've got an entity, Contact, that has a to-many relationship with another entity, Rule. In my root view controller, I use a fetched results controller to manage and display the list of Contacts. When a Contact is tapped, I push a new view controller onto the stack with a list of the Contact's Rules. I have not been able to figure out how to use a second fetched results controller to display the Rules, so I'm using the following: // create a set of the contact's rules rules = [NSMutableSet set]; rules = [self.contact mutableSetValueForKey:@"rule"]; // create an array of rules from the set arrayOfRules = [NSMutableArray arrayWithCapacity:[rules count]]; for (id oneObject in rules) [arrayOfRules addObject:oneObject]; // sort the array of rules NSSortDescriptor *descriptor = [[NSSortDescriptor alloc] initWithKey:@"phoneLabel" ascending:YES]; [arrayOfRules sortUsingDescriptors:[NSArray arrayWithObject:descriptor]]; [descriptor release]; I create a set of Rules, then use that to create an array of Rules for sorting. I then use these two collections to populate the grouped table view. All of this appears to be working correctly. Here's my problem: There are several different actions a user can take in this view, and most of them require that I know which Rule was tapped. But I can't figure out how to get that. For instance, say a user wants to delete a Rule. It seems to me the proper approach is something like... [rules removeObject:ruleObjectToBeRemoved] ...but I can't figure out how to specifiy ruleObjectToBeRemoved. I hope all of this makes sense. As usual, thanks in advance for any advice you can offer.

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• Need help with simple NHibernate mapping...

  - by mplarsen

  Need help with a simple NHibernate relationship... Tables/Classes Request ------- RequestId Title … Keywords ------- RequestID (key) Keyword (key) Request mapping file <?xml version="1.0" encoding="utf-8" ?> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" namespace="CR.Model" assembly="CR"> <class name="CR.Model.Request, CR table="[dbo].[Request]" lazy="true"> <id name="Id" column="[RequestID]"> <generator class="native" /> </id> <property name="RequestorID" column="[RequestorID]" /> <property name="RequestorOther" column="[RequestorOther]" /> … Keyword?? </class> </hibernate-mapping> How do I simply map multiple keywords to a request? I don't need another mapping file for the keyword class, do I? It's be great if I could not only get the associated keywords, but add them too...

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• EF4 querying through the generations

  - by Hans Kesting

  I have a model withs Parents, Children and Grandchildren, in a many-to-many relationship. Using this article I created POCO classes that work fine, except for one thing I can't yet figure out. When I query the Parents or Children directly using LINQ, the SQL reflects the LINQ query (a .Count() executes a COUNT in the database and so on) - fine. The Parent class has a Children property, to access it's children. But (and now for the problem) this doesn't expose an IQueryable interface but an ICollection. So when I access the Children property on a particular parent all the Parent's Children are read. Even worse, when I access the Grandchildren (theParent.Children.SelectMany(child => child.GrandChildren).Count()) then for each and every child a separate request is issued to select it's grandchildren. Changing the type of the Children property from ICollection to IQueryable doesn't solve this. Apart from missing needed methods like Add() and Remove(), EF just doesn't recognize the property then. Are there correct ways (as in: low database interaction) of querying through children (and what are they)? Or is this just not possible?

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• Joining tables with composite keys in a legacy system in hibernate

  - by Steve N

  Hi, I'm currently trying to create a pair of Hibernate annotated classes to load (read only) from a pair of tables in a legacy system. The legacy system uses a consistent (if somewhat dated) approach to keying tables. The tables I'm attempting to map are as follows: Customer CustomerAddress -------------------------- ---------------------------- customerNumber:string (pk) customerNumber:string (pk_1) name:string sequenceNumber:int (pk_2) street:string postalCode:string I've approached this by creating a CustomerAddress class like this: @Entity @Table(name="CustomerAddress") @IdClass(CustomerAddressKey.class) public class CustomerAddress { @Id @AttributeOverrides({ @AttributeOverride(name = "customerNumber", column = @Column(name="customerNumber")), @AttributeOverride(name = "sequenceNumber", column = @Column(name="sequenceNumber")) }) private String customerNumber; private int sequenceNumber; private String name; private String postalCode; ... } Where the CustomerAddressKey class is a simple Serializable object with the two key fields. The Customer object is then defined as: @Entity @Table(name = "Customer") public class Customer { private String customerNumber; private List<CustomerAddress> addresses = new ArrayList<CustomerAddress>(); private String name; ... } So, my question is: how do I express the OneToMany relationship on the Customer table?

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• NHibernate with string primary key and relationships

  - by John_

  I've have just been stumped with this problem for an hour and I annoyingly found the problem eventually. THE CIRCUMSTANCES I have a table which users a string as a primary key, this table has various many to one and many to many relationships all off this primary key. When searching for multiple items from the table all relationships were brought back. However whenever I tried to get the object by the primary key (string) it was not bringing back any relationships, they were always set to 0. THE PARTIAL SOLUTION So I looked into my logs to see what the SQL was doing and that was returning the correct results. So I tried various things in all sorts of random ways and eventually worked out it was. The case of the string being passed into the get method was not EXACTLY the same case as it was in the database, so when it tried to match up the relationship items with the main entity it was finding nothing (Or at least NHIbernate wasn't because as I stated above the SQL was actually returning the correct results) THE REAL SOLUTION Has anyone else come across this? If so how do you tell NHibernate to ignore case when matching SQL results to the entity? It is silly because it worked perfectly well before now all of a sudden it has started to pay attention to the case of the string.

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• Triangulation in 3D Space

  - by w3b_wizzard

  Disclaimer: This is for class, however I'm fresh out of ideas and a nudge in the right direction would be much appreciated. Also, this needs to be implemented in raw C, so no fancy libraries can be used. I have to write a search and rescue simulator for submarines, it has to find a probe that is randomly placed in 3D space in a grid from of the MAX_XYZ (100000). The only tools I'm given are a "ping" which will give the magnitude of the distance between a certain sub and the probe. The goal is to optimize the costs of this entire operation so a brute force attempt, like looking at every single coordinate, won't work. Hence I was thinking triangulation. Now, it makes loads of sense to me, place three subs, each one of them uses their ping to get the distance between them and the probe. Since each sub have a known distance relative to one another, it's easy to build the base of a tetrahedron with them, and the results of the ping will point to a certain coordinate, the problem I'm having is how to figure out the elevation, or the height, of the tetrahedron. So what I have as data is the following: Distances between subs (In vector format) Angles between each subs (very easy to compute) Distance between each sub and the probe (3 segments from the base to the peak) Angles inside each of the outer 3 surfaces of the tetrahedron. I tried finding some sort of relationship with the vertices of the tetrahedron and the relative angles in each of them, however all I found had to deal with tetrahedrons built with equilateral triangles, which isn't much help. I have the impression this can be easily solved with trig but either I'm not seeing it or I need more coffee. Any suggestions would be appreciated!

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• [Rails] Accessing error_messages on form_tag

  - by aaronrussell

  I have built a custom form for creating a joining model on a has_many :through relationship. The models look roughly like this: class Team has_many :team_members has_many :members, :through => :team_members end class Member has_many :team_members has_many :teams, :through => :team_members end class TeamMember belongs_to :team belongs_to :member # and this model has some validations too end The form I have built is for selecting which members should be in a team. I won't paste the form, but it uses the form_tag method and basically sends an array of hashes which contain a member_id and a squad_number. I then update the database with an action that looks roughly like this (simplified a bit, but you get the jist): @team.transaction do @team.team_members = params[:team_members].collect{|tm| @team.team_members.new(tm)} if @team.save redirect_to ... else render :action => :members end end Everything works great but I am validating the squad_number for uniqueness and numerically. So, when any of those validations fail, how do I get access to them in my view, and how do I ascertain which of the many members it has failed on?

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• Retrieving Relationships from within two arrays of pointers

  - by DanF

  In a portion of a program I'm working on, I need to count all the times each person has worked on projects with each other person. Let's say we have "Employee" entities and "Session" entities. In each session, there are four project types, "A", "B", "C", & "D", each a many-to-many relationship to Employees. I'm making a loop to systematically review every person a selected person has worked with. First, I put all their project types in a single array, so it's easier to loop through, but by the time I ask the last nested Project for its Employee members, I get an "unrecognized selector" error. IBOutlet NSArrayController * list; int x; for(x = 0; x < [list count]; x++){ NSArray *A = [[list objectAtIndex:x] valueForKey:@"projectAs"]; NSArray *A = [[list objectAtIndex:x] valueForKey:@"projectBs"]; NSArray *A = [[list objectAtIndex:x] valueForKey:@"projectCs"]; NSArray *A = [[list objectAtIndex:x] valueForKey:@"projectDs"]; NSArray *masterList = [[NSArray alloc] initWithObjects: projectAs, projectBs, projectCs, projectDs, nil]; int y; for(y = 0; y < [masterList count]; y++){ int z; for(z = 0; z < [[masterlist objectAtIndex:y] count]; z++){ //And now to make an Array of this employee's partners on the selected object, to run comparisons on. //I also have an array of keys for each session's teams, so that's what I'm referencing here: NSArray * thisTeam = [list objectAtIndex:y] objectAtIndex:z] valueForKey:projectKey]; This throws an exception... namely, -[_NSFaultingMutableSet objectAtIndex:]: unrecognized selector sent to instance What's wrong with that last Array creation?

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• Using the JPA Criteria API, can you do a fetch join that results in only one join?

  - by Shaun

  Using JPA 2.0. It seems that by default (no explicit fetch), @OneToOne(fetch = FetchType.EAGER) fields are fetched in 1 + N queries, where N is the number of results containing an Entity that defines the relationship to a distinct related entity. Using the Criteria API, I might try to avoid that as follows: CriteriaBuilder builder = entityManager.getCriteriaBuilder(); CriteriaQuery<MyEntity> query = builder.createQuery(MyEntity.class); Root<MyEntity> root = query.from(MyEntity.class); Join<MyEntity, RelatedEntity> join = root.join("relatedEntity"); root.fetch("relatedEntity"); query.select(root).where(builder.equals(join.get("id"), 3)); The above should ideally be equivalent to the following: SELECT m FROM MyEntity m JOIN FETCH myEntity.relatedEntity r WHERE r.id = 3 However, the criteria query results in the root table needlessly being joined to the related entity table twice; once for the fetch, and once for the where predicate. The resulting SQL looks something like this: SELECT myentity.id, myentity.attribute, relatedentity2.id, relatedentity2.attribute FROM my_entity myentity INNER JOIN related_entity relatedentity1 ON myentity.related_id = relatedentity1.id INNER JOIN related_entity relatedentity2 ON myentity.related_id = relatedentity2.id WHERE relatedentity1.id = 3 Alas, if I only do the fetch, then I don't have an expression to use in the where clause. Am I missing something, or is this a limitation of the Criteria API? If it's the latter, is this being remedied in JPA 2.1 or are there any vendor-specific enhancements? Otherwise, it seems better to just give up compile-time type checking (I realize my example doesn't use the metamodel) and use dynamic JPQL TypedQueries.

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• Mapping many-to-many association table with extra column(s)

  - by user635524

  My database contains 3 tables: User and Service entities have many-to-many relationship and are joined with the SERVICE_USER table as follows: USERS - SERVICE_USER - SERVICES SERVICE_USER table contains additional BLOCKED column. What is the best way to perform such a mapping? These are my Entity classes @Entity @Table(name = "USERS") public class User implements java.io.Serializable { private String userid; private String email; @Id @Column(name = "USERID", unique = true, nullable = false,) public String getUserid() { return this.userid; } .... some get/set methods } @Entity @Table(name = "SERVICES") public class CmsService implements java.io.Serializable { private String serviceCode; @Id @Column(name = "SERVICE_CODE", unique = true, nullable = false, length = 100) public String getServiceCode() { return this.serviceCode; } .... some additional fields and get/set methods } I followed this example http://giannigar.wordpress.com/2009/09/04/m ... using-jpa/ Here is some test code: User user = new User(); user.setEmail("e2"); user.setUserid("ui2"); user.setPassword("p2"); CmsService service= new CmsService("cd2","name2"); List<UserService> userServiceList = new ArrayList<UserService>(); UserService userService = new UserService(); userService.setService(service); userService.setUser(user); userService.setBlocked(true); service.getUserServices().add(userService); userDAO.save(user); The problem is that hibernate persists User object and UserService one. No success with the CmsService object I tried to use EAGER fetch - no progress Is it possible to achieve the behaviour I'm expecting with the mapping provided above? Maybe there is some more elegant way of mapping many to many join table with additional column?

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• For a 1view/scene to 2view/scene app, what application should I choose in Xcode?

  - by Tony Xu

  The question may be simple to some others, but I have been struggling with this for a while. The app I want would be like this: first scene/view with two big buttons (no toolbar item), click each one to get into two new scenes. So totally three scenes. In Xcode, what application should I choose? And in storyboard how/should I drag/draw? Thanks. Update: thanks for the link, the big-number-user. I actually read that tutorial before I asked. A little update on what I got so far: 1, I selected "single view", so there's view controller 1 (VC1) in the storyboard. 2, dragged a navigation controller (NC), and move the initial view arrow pointing to NC 3, control-drag to link NC and VC1, selected "relationship segue root view controller" when some small dialog popup. IS THIS CORRECT? 4, created two additional VC, VC3 and VC4, control-drag link each to NC. selected "push", IS THIS CORRECT? 5, in VC1, I added two buttons, showVC3 and showVC4. NOW I DON'T KNOW how to add IBAction to button showVC3 and showVC4. I tried to control-drag it to ViewController.m file @interface and @end section, but failed. What should I do next?

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• Saving Data to Relational Database (Entity Framework)

  - by sheefy

  I'm having a little bit of trouble saving data to a database. Basically, I have a main table that has associations to other tables (Example Below). Tbl_Listing ID UserID - Associated to ID in User Table CategoryID - Associated to ID in Category Table LevelID - Associated to ID in Level Table. Name Address Normally, it's easy for me to add data to the DB (using Entity Framework). However, I'm not sure how to add data to the fields with associations. The numerous ID fields just need to hold an int value that corresponds with the ID in the associated table. For example; when I try to access the column in the following manner I get a "Object reference not set to an instance of an object." error. Listing NewListing = new Listing(); NewListing.Tbl_User.ID = 1; NewListing.Tbl_Category.ID = 2; ... DBEntities.AddToListingSet(NewListing); DBEntities.SaveChanges(); I am using NewListing.Tbl_User.ID instead of NewListing.UserID because the UserID field is not available through intellisense. If I try and create an object for each related field I get a "The relationship between the two objects cannot be defined because they are attached to different ObjectContext objects." error. With this method, I am trying to add the object without the .ID shown above - example NewListing.User = UserObject. I know this should be simple as I just want to reference the ID from the associated table in the main Listing's table. Any help would be greatly appreciated. Thanks in advance, -S

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• I need help with a SQL query. Fetching an entry, it's most recent revision and it's fields.

  - by Tigger ate my dad

  Hi there, I'm building a CMS for my own needs, and finished planning my database layout. Basically I am abstracting all possible data-models into "sections" and all entries into one table. The final layout is as follows: Database diagram: I have yet to be allowed to post images, so here is a link to a diagram of my database. Entries (section_entries) are children of their section (sections). I save all edits to the entries in a new revision (section_entries_revisions), and also track revisions on the sections (section_revisions), in order to match the values of a revision, to the fields of the section that existed when the entry-revision was made. The section-revisions can have a number of fields (section_revision_fields) that define the attributes of entries in the section. There is a many-to-many relationship between the fields (section_revision_fields) and the entry-revisions (section_entry_revisions), that stores the values of the attributes defined by the section revision. Feel free to ask questions if the diagram is confusing. Now, this is the most complex SQL I've ever worked with, and the task of fetching my data is a little daunting. Basically what i want help with, is fetching an entry, when the only known variables are; section_id, section_entry_id. The query should fetch the most recent revision of that entry, and the section_revision model corresponding to section_revision_id in the section_entry_revisions table. It should also fetch the values of the fields in the section-revision. I was hoping for a query result, where there would be as many rows as fields in the section. Each row would contain the information of the entry and the section, and then information for one of the fields (e.g. each row corresponding to a field and it's value). I tried to explain the best I could. Again, feel free to ask questions if my description somehow lacking. I hope someone is up for the challenge. Best regards. :-)

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• How to map this class in NHibernate (not FluentNHibernate)?

  - by JMSA

  Suppose I have a database like this: This is set up to give role-wise menu permissions. Please note that, User-table has no direct relationship with Permission-table. Then how should I map this class against the database-tables? class User { public int ID { get; set; } public string Name { get; set; } public string Username { get; set; } public string Password { get; set; } public bool? IsActive { get; set; } public IList<Role> RoleItems { get; set; } public IList<Permission> PermissionItems { get; set; } public IList<string> MenuItemKeys { get; set; } } This means, (1) Every user has some Roles. (2) Every user has some Permissions (depending on to Roles). (3) Every user has some permitted MenuItemKeys (according to Permissions). How should my User.hbm.xml look like?

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• What db fits me?

  - by afvasd

  Dear Everyone I am currently using mysql. I am finding that my schema is getting incredibly complicated. I seek to find a new db that will suit my needs: Let's assume I am building a news aggregrator (which collects news from multiple website). I then run algorithms to determine if two news from different sites are actually referring to the same topic. I run this algorithm to cluster news together. The relationship is depicted below: cluster \--news1 \--word1 \--word2 \--news2 \--word3 \--news3 \--word1 \--word3 And then I will apply some magic and determine the importance of each word. Summing all the importance of each word gives me the importance of a news article. Summing the importance of each news article gives me the importance of a cluster. Note that above cluster there are also subgroups( like split by region etc), and categories (like sports, etc) which I have to determine the importance of that in a particular day per se. I have used views in the past to do so, but I realized that views are very slow. So i will normally do an insert into an actual table and index them for better performance. As you can see this leads to multiple tables derived like (cluster, importance), (news, importance), (words, importance) etc which can get pretty messy. Also the "importance" metric will change. It has become increasingly difficult to alter tables, update data (which I am using TRUNCATE TABLE) and then inserting from null. I am currently looking into something schemaless like Mongodb. I do not need distributedness. I would very much want something that is reasonably fast (which can be indexed) and something that is a lot more flexible that traditional RDMBS. Also, I need something that has some kind of ORM because I personally like ORM a lot. I am currently using sqlalchemy Please help!

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