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  • How to declare a generic constraint that is a generic type

    - by HackedByChinese
    I have a two generic abstract types: Entity and Association. Let's say Entity looks like this: public class Entity<TId> { //... } and Association looks like this: public class Association<TEntity, TEntity2> { //... } How do I constrain Association so they can be of any Entity? I can accomplish it by the following: public class Association<TEntity, TId, TEntity2, TId2> where TEntity : Entity<TId> where TEntity2: Entity<TId2> { //... } This gets very tedious as more types derive from Association, because I have to keep passing down TId and TId2. Is there a simpler way to do this, besides just removing the constraint?

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  • Grails: Property Null error

    - by richardhell
    I've a domain called Modulo with some properties and a Controller with a method that create a object from model and save it, when execute save the shell show this error: La propiedad [{0}] de la clase [{1}] no puede ser nulo But if i set the constraint nullable to true, the error show again. I think that i should not set this cosntraint. The model is linked to a mysql table with all properties except id allow null. I think I am not doing something wrong here. Any advice?? Domain: Modulo class Modulo { String nombre String icon String url //static constraint = { // url(nullable:true) //} } Controller: Example class ExampleController { def index = { def modulo = new Modulo( nombre:'xxx', icon:'xxx' ) if (modulo.save()){ println 'ok' }else{ modulo.errors.allErrors.each { println it.defaultMessage} } } } Thanks. José

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  • SQL DROP TABLE foreign key constraint

    - by Polly Hollanger
    If I want to delete all the tables in my database like this, will it take care of the foreign key constraint? If not, how do I take care of that first? GO IF OBJECT_ID('dbo.[Course]','U') IS NOT NULL DROP TABLE dbo.[Course] GO IF OBJECT_ID('dbo.[Student]','U') IS NOT NULL DROP TABLE dbo.[Student]

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  • Can I constrain a route parameter to a certain type in ASP.net MVC?

    - by Paul Suart
    I have the following route: routes.MapRoute( "Search", // Route name "Search/{affiliateId}", // URL with parameters new { controller = "Syndication", action = "Search" } // Parameter defaults ); Is there a way I can ensure "affiliateId" is a valid Guid? I'm using MVCContrib elsewhere in my site and I'm fairly it provides a way to implement this kind of constraint.... I just don't know what it is!

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  • Having constrains object to move X,Y at the same time?

    - by Hwang
    The stage is separated into 4 sections, and I will be moving the camera around the stage. So at each particular section the camera will have an area of constrain it can move. I mange to constrain its X & Y, but it could only navigate either X or Y. How to move in X+Y at the same time? if (mouseX>sec2maxX) { TweenLite.to(vC, 1, {x:sec2maxX}); } else if (mouseX<sec2minX) { TweenLite.to(vC, 1, {x:sec2minX}); } else { TweenLite.to(vC, 1, {x:mouseX}); } if (mouseY<sec2minY) { TweenLite.to(vC, 1, {y:sec2minY}); } else if (mouseY>sec2maxY) { TweenLite.to(vC, 1, {y:sec2maxY}); } else { TweenLite.to(vC, 1, {y:mouseY}); } if i were to put X & Y in a same line of code it would be a lot of possibilities when the mouse is on top left or right bottom kind of situation, so I need to have it running seperately, but how can I combine it so that it could move X+Y?

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  • Why is TRest in Tuple<T1... TRest> not constrained?

    - by Anthony Pegram
    In a Tuple, if you have more than 7 items, you can provide an 8th item that is another tuple and define up to 7 items, and then another tuple as the 8th and on and on down the line. However, there is no constraint on the 8th item at compile time. For example, this is legal code for the compiler: var tuple = new Tuple<int, int, int, int, int, int, int, double> (1, 1, 1, 1, 1, 1, 1, 1d); Even though the intellisense documentation says that TRest must be a Tuple. You do not get any error when writing or building the code, it does not manifest until runtime in the form of an ArgumentException. You can roughly implement a Tuple in a few minutes, complete with a Tuple-constrained 8th item. I just wonder why it was left off the current implementation? Is it possibly a forward-compatibility issue where they could add more elements with a hypothetical C# 5? Short version of rough implementation interface IMyTuple { } class MyTuple<T1> : IMyTuple { public T1 Item1 { get; private set; } public MyTuple(T1 item1) { Item1 = item1; } } class MyTuple<T1, T2> : MyTuple<T1> { public T2 Item2 { get; private set; } public MyTuple(T1 item1, T2 item2) : base(item1) { Item2 = item2; } } class MyTuple<T1, T2, TRest> : MyTuple<T1, T2> where TRest : IMyTuple { public TRest Rest { get; private set; } public MyTuple(T1 item1, T2 item2, TRest rest) : base(item1, item2) { Rest = rest; } } ... var mytuple = new MyTuple<int, int, MyTuple<int>>(1, 1, new MyTuple<int>(1)); // legal var mytuple2 = new MyTuple<int, int, int>(1, 2, 3); // illegal

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  • Generic Type constraint in .net

    - by Jose
    Okay I'm looking for some input, I'm pretty sure this is not currently supported in .NET 3.5 but here goes. I want to require a generic type passed into my class to have a constructor like this: new(IDictionary<string,object>) so the class would look like this public MyClass<T> where T : new(IDictionary<string,object>) { T CreateObject(IDictionary<string,object> values) { return new T(values); } } But the compiler doesn't support this, it doesn't really know what I'm asking. Some of you might ask, why do you want to do this? Well I'm working on a pet project of an ORM so I get values from the DB and then create the object and load the values. I thought it would be cleaner to allow the object just create itself with the values I give it. As far as I can tell I have two options: 1) Use reflection(which I'm trying to avoid) to grab the PropertyInfo[] array and then use that to load the values. 2) require T to support an interface like so: public interface ILoadValues { void LoadValues(IDictionary values); } and then do this public MyClass<T> where T:new(),ILoadValues { T CreateObject(IDictionary<string,object> values) { T obj = new T(); obj.LoadValues(values); return obj; } } The problem I have with the interface I guess is philosophical, I don't really want to expose a public method for people to load the values. Using the constructor the idea was that if I had an object like this namespace DataSource.Data { public class User { protected internal User(IDictionary<string,object> values) { //Initialize } } } As long as the MyClass<T> was in the same assembly the constructor would be available. I personally think that the Type constraint in my opinion should ask (Do I have access to this constructor? I do, great!) Anyways any input is welcome.

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  • [CODE GENERATION] How to generate DELETE statements in PL/SQL, based on the tables FK relations?

    - by The chicken in the kitchen
    Is it possible via script/tool to generate authomatically many delete statements based on the tables fk relations, using Oracle PL/SQL? In example: I have the table: CHICKEN (CHICKEN_CODE NUMBER) and there are 30 tables with fk references to its CHICKEN_CODE that I need to delete; there are also other 150 tables foreign-key-linked to that 30 tables that I need to delete first. Is there some tool/script PL/SQL that I can run in order to generate all the necessary delete statements based on the FK relations for me? (by the way, I know about cascade delete on the relations, but please pay attention: I CAN'T USE IT IN MY PRODUCTION DATABASE, because it's dangerous!) I'm using Oracle DataBase 10G R2. This is the result I've written, but it is not recursive: This is a view I have previously written, but of course it is not recursive! CREATE OR REPLACE FORCE VIEW RUN ( OWNER_1, CONSTRAINT_NAME_1, TABLE_NAME_1, TABLE_NAME, VINCOLO ) AS SELECT OWNER_1, CONSTRAINT_NAME_1, TABLE_NAME_1, TABLE_NAME, '(' || LTRIM ( EXTRACT (XMLAGG (XMLELEMENT ("x", ',' || COLUMN_NAME)), '/x/text()'), ',') || ')' VINCOLO FROM ( SELECT CON1.OWNER OWNER_1, CON1.TABLE_NAME TABLE_NAME_1, CON1.CONSTRAINT_NAME CONSTRAINT_NAME_1, CON1.DELETE_RULE, CON1.STATUS, CON.TABLE_NAME, CON.CONSTRAINT_NAME, COL.POSITION, COL.COLUMN_NAME FROM DBA_CONSTRAINTS CON, DBA_CONS_COLUMNS COL, DBA_CONSTRAINTS CON1 WHERE CON.OWNER = 'TABLE_OWNER' AND CON.TABLE_NAME = 'TABLE_OWNED' AND ( (CON.CONSTRAINT_TYPE = 'P') OR (CON.CONSTRAINT_TYPE = 'U')) AND COL.TABLE_NAME = CON1.TABLE_NAME AND COL.CONSTRAINT_NAME = CON1.CONSTRAINT_NAME --AND CON1.OWNER = CON.OWNER AND CON1.R_CONSTRAINT_NAME = CON.CONSTRAINT_NAME AND CON1.CONSTRAINT_TYPE = 'R' GROUP BY CON1.OWNER, CON1.TABLE_NAME, CON1.CONSTRAINT_NAME, CON1.DELETE_RULE, CON1.STATUS, CON.TABLE_NAME, CON.CONSTRAINT_NAME, COL.POSITION, COL.COLUMN_NAME) GROUP BY OWNER_1, CONSTRAINT_NAME_1, TABLE_NAME_1, TABLE_NAME; ... and it contains the error of using DBA_CONSTRAINTS instead of ALL_CONSTRAINTS...

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  • Namespace constraint with generic class decleration

    - by SomeGuy
    Good afternoon people, I would like to know if (and if so how) it is possible to define a namespace as a constraint parameter in a generic class declaration. What I have is this: namespace MyProject.Models.Entities <-- Contains my classes to be persisted in db namespace MyProject.Tests.BaseTest <-- Obvious i think Now the decleration of my 'BaseTest' class looks like so; public class BaseTest<T> This BaseTest does little more (at the time of writing) than remove all entities that were added to the database during testing. So typically I will have a test class declared as: public class MyEntityRepositoryTest : BaseTest<MyEntity> What i would LIKE to do is something similar to the following: public class BaseTest<T> where T : <is of the MyProject.Models.Entities namespace> Now i am aware that it would be entirely possible to simply declare a 'BaseEntity' class from which all entities created within the MyProject.Models.Entities namespace will inherit from; public class BaseTest<T> where T : MyBaseEntity but...I dont actually need to, or want to. Plus I am using an ORM and mapping entities with inheritance, although possible, adds a layer of complexity that is not required. So, is it possible to constrain a generic class parameter to a namespace and not a specific type ? Thank you for your time.

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  • How to do multiple column UniqueConstraint in hbm?

    - by DataSurfer
    Working on some legacy hibernate code. How do I do the following with hbm.xml(hibernate mapping file) instead of with annotations? @Table(name="users", uniqueConstraints = { @UniqueConstraint(columnNames={"username", "client"}), @UniqueConstraint(columnNames={"email", "client"}) }) public class User implements Serializable { private static final long serialVersionUID = 1L; @Id private int id; private String username; private String email; private Client client; }

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  • XForms relation of 'constraint' and 'required' properties

    - by Danny
    As a reference, the most similar question already asked is: http://stackoverflow.com/questions/8667849/making-xforms-enforce-the-constraint-and-type-model-item-properties-only-when-fi The difference is that I cannot use the relevant properties since I do want the field to be visible and accessible. I'm attempting to make a XForms form that has the following properties: It displays a text field named 'information'. (for the example) This field must not be required, since it may not be necessary to enter data. (Or this data will be entered at a later time.) However, if data is entered in this field, it must adhere to the specified constraint. I cannot mark the field as not relevant since this would hide the field and some data may need to be entered in it. The trouble now is that even though the field has no data in it, the constraint is still enforced (i.e. even though it is not marked as 'required'). I have taken a look at the XForms 1.1 specification, however it does not seem to describe how the properties 'required' and 'constraint' should interact. The only option I see, is to add a part to the constraint such that an empty value is allowed. e.g.: . = '' or <actual-constraint However, I don't like this. It feels like a workaround to add this to every such field. Is there any other way to express that non-required fields should not need to match the constraint for that field? (Am I missing something?)

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  • MySQL Removing Some Foreign keys

    - by Drew
    I have a table whose primary key is used in several other tables and has several foreign keys to other tables. CREATE TABLE location ( locationID INT NOT NULL AUTO_INCREMENT PRIMARY KEY ... ) ENGINE = InnoDB; CREATE TABLE assignment ( assignmentID INT NOT NULL AUTO_INCREMENT PRIMARY KEY, locationID INT NOT NULL, FOREIGN KEY locationIDX (locationID) REFERENCES location (locationID) ... ) ENGINE = InnoDB; CREATE TABLE assignmentStuff ( ... assignmentID INT NOT NULL, FOREIGN KEY assignmentIDX (assignmentID) REFERENCES assignment (assignmentID) ) ENGINE = InnoDB; The problem is that when I'm trying to drop one of the foreign key columns (ie locationIDX) it gives me an "ERROR 1025 (HY000): Error on rename" error. How can I drop the column in the assignment table above without getting this error?

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  • T-SQL Unique constraint locked the SQL server

    - by PaN1C_Showt1Me
    HI ! This is my table: CREATE TABLE [ORG].[MyTable]( .. [my_column2] UNIQUEIDENTIFIER NOT NULL CONSTRAINT FK_C1 REFERENCES ORG.MyTable2 (my_column2), [my_column3] INT NOT NULL CONSTRAINT FK_C2 REFERENCES ORG.MyTable3 (my_column3) .. ) I've written this constraint to assure that combination my_column2 and my_column3 is always unique. ALTER TABLE [ORG].[MyTable] ADD CONSTRAINT UQ_MyConstraint UNIQUE NONCLUSTERED ( my_column2, my_column3 ) But then suddenly.. The DB stopped responding.. there is a lock or something.. Do you have any idea why? What is bad with the constraint?

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  • Grails' GORM constraint question

    - by xain
    Hi, I have the following Domain Class: class Metric { String name float value static belongsTo = [Person,Corporation] static indexes = { name() } } How can I add a constraint so Person,Corporation and name are unique ? Thanks.

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  • how can i set up a uniqueness constraint in mysql for columns that can be null?

    - by user299689
    I know that in MySQL, UNIQUE constraits don't treat NULL values as equal. So if I have a unique constraint on ColumnX, then two separate rows can have values of NULL for ColumnX and this wouldn't violate the constraint. How can I work around this? I can't just set the value to an arbitrary constant that I can flag, because ColumnX in my case is actually a foreign key to another table. What are my options here? Please note that this table also has an "id" column that is its primary key. Since I'm using Ruby on Rails, it's important to keep this id column as the primary key. Note 2: In reality, my unique key encompasses many columns, and some of them have to be null, because they are foreign keys, and only one of them should be non-null. What I'm actually trying to do is to "simulate" a polymorphic relationship in a way that keep referential integrity in the db, but using the technique outlined in the first part of the question asked here: http://stackoverflow.com/questions/922184/why-can-you-not-have-a-foreign-key-in-a-polymorphic-association

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  • How do I make a GUI that behaves like this?

    - by Karl Knechtel
    This is difficult to explain without illustration, so - behold, an illustration, cobbled together from screenshots of a few hello-world examples and a lot of Paint work: I have started out using Windows Forms on .NET (via IronPython, but that shouldn't be important), and haven't been able to figure out very much. GUI libraries in general are very intimidating, simply because every class has so many possible attributes. Documentation is good at explaining what everything does, but not so good at helping you figure out what you need. I will be assembling the GUI dynamically, but I'm not expecting that to be the hard part. The sticking points for me right now are: How do I get text labels to size themselves automatically to the width of the contained text (so that the text doesn't clip, and I also don't reserve unnecessary space for them when resizing the window)? How do I make the vertical scrollbar always appear? Setting the VScroll property (why is this protected when AutoScroll is public, BTW?) doesn't seem to do anything. How come the horizontal scrollbar is not added by AutoScroll when contents are laid out vertically (via Dock = DockStyle.Top)? I can use a minimum size for panels to prevent the label and corresponding control from overlapping when the window is shrunk horizontally, but then the scrollbar doesn't appear and the control is inaccessible. How can I put limits on window resizing (e.g. set a minimum width) without disabling it completely? (Just set minimum/maximum sizes for the Form?) Related to that, is there any way to set minimum/maximum widths or heights without setting a minimum/maximum size (i.e. can I constrain the size in only one dimension)? Is there a built-in control suitable for hex editing or am I going to have to build something myself? ... And should I be using something else (perhaps something more capable?) I've heard WPF mentioned, but I understand that this involves XML and I really want to build a GUI from XML - I already have data in an object graph, and doing some kind of weird XML pseudo-serialization (in Python, no less!) in order to create a GUI seems incredibly roundabout.

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  • Symfony 1.4: Deleting a sfGuardUser

    - by Tom
    Hi, I'm having some trouble with the following... I have a sfGuardUser table set up normally, and it has a one-to-one relationship with a Profile table, which contains some additional user info. When a user wants to delete themselves from the site, I'd like to retain their info in the Profile table for various purposes BUT delete the sfGuardUser in order to keep that table cleaner/shorter (not just set it to inactive). I was under the impression that I could set the FK in the Profile table to NULL and then delete the sfGuardUser, but it seems the FK-constraint fails. Indeed, it seems I can't delete either and the queries fail: If I try to delete the sfGuardUser, the Profile table will have an invalid FK If I try to delete a Profile, the sfGuardUser will have an invalid FK Other than leaving outdated sfGuardUsers and Profiles in these tables, or having to use a cascaded delete to get rid of both, can anyone tell me if there's any other way around this? Thank you.

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  • Unable to drop constraint in sql server 2005 "Could not drop constraint. See previous errors"

    - by DannykPowell
    I'm trying to drop a constraint on a db table, something like: ALTER TABLE MyTable drop CONSTRAINT FK_MyTable_AnotherTable But the execution just runs and runs. If I stop it I see: Msg 3727, Level 16, State 0, Line 2 Could not drop constraint. See previous errors. Web search throws up various pages but note that the constraint is properly named and I am trying to remove it using the correct name

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  • How should I do this (business logic) in Sql Server? A constraint?

    - by Pure.Krome
    Hi folks, I wish to add some type of business logic constraint to a table, but not sure how / where. I have a table with the following fields. ID INTEGER IDENTITY HubId INTEGER CategoryId INTEGER IsFeatured BIT Foo NVARCHAR(200) etc. So what i wish is that you can only have one featured thingy, per articleId + hubId. eg. 1, 1, 1, 1, 'blah' -- Ok. 2, 1, 2, 1, 'more blah' -- Also Ok 3, 1, 1, 1, 'aaa' -- constraint error 4, 1, 1, 0, 'asdasdad' -- Ok. 5, 1, 1, 0, 'bbbb' -- Ok. etc. so the third row to be inserterd would fail because that hub AND category already have a featured thingy. Is this possible?

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  • Why can I create a table with PRIMARY KEY on a nullable column?

    - by AlexKuznetsov
    The following code creates a table without raising any errors: CREATE TABLE test( ID INTEGER NULL, CONSTRAINT PK_test PRIMARY KEY(ID) ) Note that I cannot insert a NULL, as expected: INSERT INTO test VALUES(1),(NULL) ERROR: null value in column "id" violates not-null constraint DETAIL: Failing row contains (null). ********** Error ********** ERROR: null value in column "id" violates not-null constraint SQL state: 23502 Detail: Failing row contains (null). Why can I create a table with a self-contradictory definition? ID column is explicitly declared as NULLable, and it is implicitly not nullable, as a part of the PRIMARY KEY. Does it make sense? Edit: would it not be better if this self-contradictory CREATE TABLE just failed right there?

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  • C# overloading with generics: bug or feature?

    - by TN
    Let's have a following simplified example: void Foo<T>(IEnumerable<T> collection, params T[] items) { // ... } void Foo<C, T>(C collection, T item) where C : ICollection<T> { // ... } void Main() { Foo((IEnumerable<int>)new[] { 1 }, 2); } Compiler says: The type 'System.Collections.Generic.IEnumerable' cannot be used as type parameter 'C' in the generic type or method 'UserQuery.Foo(C, T)'. There is no implicit reference conversion from 'System.Collections.Generic.IEnumerable' to 'System.Collections.Generic.ICollection'. If I change Main to: void Main() { Foo<int>((IEnumerable<int>)new[] { 1 }, 2); } It will work ok. Why compiler does not choose the right overload?

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