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  • creating a vector with references to some of the elements of another vector

    - by memC
    hi, I have stored instances of class A in a std:vector, vec_A as vec_A.push_back(A(i)). The code is shown below. Now, I want to store references some of the instances of class A (in vec_A) in another vector or another array. For example, if the A.getNumber() returns 4, 7, 2 , I want to put a reference to that instance of A in another vector, say std:vector<A*> filtered_A or an array. Can someone sow me how to do this?? Thanks! class A { public: int getNumber(); A(int val); ~A(){}; private: int num; }; A::A(int val){ num = val; }; int A::getNumber(){ return num; }; int main(){ int i =0; int num; std::vector<A> vec_A; for ( i = 0; i < 10; i++){ vec_A.push_back(A(i)); } std::cout << "\nPress RETURN to continue..."; std::cin.get(); return 0; }

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  • Satisfying indirect references at runtime.

    - by automatic
    I'm using C# and VS2010. I have a dll that I reference in my project (as a dll reference not a project reference). That dll (a.dll) references another dll that my project doesn't directly use, let's call it b.dll. None of these are in the GAC. My project compiles fine, but when I run it I get an exception that b.dll can't be found. It's not being copied to the bin directory when my project is compiled. What is the best way to get b.dll into the bin directory so that it can be found at run time. I've thought of four options. Use a post compile step to copy b.dll to the bin directory Add b.dll to my project (as a file) and specify copy to output directory if newer Add b.dll as a dll reference to my project. Use ILMerge to combine b.dll with a.dll I don't like 3 at all because it makes b.dll visible to my project, the other two seem like hacks. Am I missing other solutions? Which is the "right" way? Would a dependency injection framework be able to resolve and load b.dll?

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  • Why is a c++ reference considered safer than a pointer?

    - by anand.arumug
    When the c++ compiler generates very similar assembler code for a reference and pointer, why is using references preferred (and considered safer) compared to pointers? I did see Difference between pointer variable and reference variable in C++ which discusses the differences between them. EDIT-1: I was looking at the assembler code generated by g++ for this small program: int main(int argc, char* argv[]) { int a; int &ra = a; int *pa = &a; }

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  • Java reference storage question

    - by aab
    In java, when you pass an object to a method as a parameter, it is actually passing a reference, or a pointer, to that object because objects in Java are references. Inside the function, it has a pointer to that object which is a location in memory. I am wondering where this pointer lives in memory? Is a new memory location created once inside the function to hold this reference?

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  • References between Spring beans when using a NameSpaceHandler

    - by teabot
    I'm trying to use a Spring context namespace to build some existing configuration objects in an application. I have defined a context and pretty much have if working satisfactorily - however, I'd like one bean defined by my namespace to implicitly reference another: Consider the class named 'Node': public Class Node { private String aField; private Node nextNode; public Node(String aField, Node nextNode) { ... } Now in my Spring context I have something like so: <myns:container> <myns:node aField="nodeOne"/> <myns:node aField="nodeTwo"/> </myns:container> Now I'd like nodeOne.getNode() == nodeTwo to be true. So that nodeOne.getNode() and nodeTwo refer to the same bean instance. These are pretty much the relevant parts I have in my AbstractBeanDefinitionParser: public AbstractBeanDefinition parseInternal(Element element, ParserContext parserContext) { ... BeanDefinitionBuilder containerFactory = BeanDefinitionBuilder.rootBeanDefinition(ContainerFactoryBean.class); List<BeanDefinition> containerNodes = Lists.newArrayList(); String previousNodeBeanName; // iterate backwards over the 'node' elements for (int i = nodeElements.size() - 1; i >= 0; --i) { BeanDefinitionBuilder node = BeanDefinitionBuilder.rootBeanDefinition(Node.class); node.setScope(BeanDefinition.SCOPE_SINGLETON); String nodeField = nodeElements.getAttribute("aField"); node.addConstructorArgValue(nodeField); if (previousNodeBeanName != null) { node.addConstructorArgValue(new RuntimeBeanReference(previousNodeBeanName)); } else { node.addConstructorArgValue(null); } BeanDefinition nodeDefinition = node.getBeanDefinition(); previousNodeBeanName = "inner-node-" + nodeField; parserContext.getRegistry().registerBeanDefinition(previousNodeBeanName, nodeDefinition); containerNodes.add(node); } containerFactory.addPropertyValue("nodes", containerNodes); } When the application context is created my Node instances are created and recognized as singletons. Furthermore, the nextNode property is populated with a Node instance with the previous nodes configuration - however, it isn't the same instance. If I output a log message in Node's constructor I see two instances created for each node bean definition. I can think of a few workarounds myself but I'm keen to use the existing model. So can anyone tell me how I can pass these runtime bean references so that I get the correct singleton behaviour for my Node instances?

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  • Using pointers, references, handles to generic datatypes, as generic and flexible as possible

    - by Patrick
    In my application I have lots of different data types, e.g. Car, Bicycle, Person, ... (they're actually other data types, but this is just for the example). Since I also have quite some 'generic' code in my application, and the application was originally written in C, pointers to Car, Bicycle, Person, ... are often passed as void-pointers to these generic modules, together with an identification of the type, like this: Car myCar; ShowNiceDialog ((void *)&myCar, DATATYPE_CAR); The 'ShowNiceDialog' method now uses meta-information (functions that map DATATYPE_CAR to interfaces to get the actual data out of Car) to get information of the car, based on the given data type. That way, the generic logic only has to be written once, and not every time again for every new data type. Of course, in C++ you could make this much easier by using a common root class, like this class RootClass { public: string getName() const = 0; }; class Car : public RootClass { ... }; void ShowNiceDialog (RootClass *root); The problem is that in some cases, we don't want to store the data type in a class, but in a totally different format to save memory. In some cases we have hundreds of millions of instances that we need to manage in the application, and we don't want to make a full class for every instance. Suppose we have a data type with 2 characteristics: A quantity (double, 8 bytes) A boolean (1 byte) Although we only need 9 bytes to store this information, putting it in a class means that we need at least 16 bytes (because of the padding), and with the v-pointer we possibly even need 24 bytes. For hundreds of millions of instances, every byte counts (I have a 64-bit variant of the application and in some cases it needs 6 GB of memory). The void-pointer approach has the advantage that we can almost encode anything in a void-pointer and decide how to use it if we want information from it (use it as a real pointer, as an index, ...), but at the cost of type-safety. Templated solutions don't help since the generic logic forms quite a big part of the application, and we don't want to templatize all this. Additionally, the data model can be extended at run time, which also means that templates won't help. Are there better (and type-safer) ways to handle this than a void-pointer? Any references to frameworks, whitepapers, research material regarding this?

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  • Passing Auth to API calls with Web Service References

    - by coffeeaddict
    I am new to web services. The last time I dealt with SOAP was when I created a bunch of wrapper classes that sent requests and received responses back per some response objects/classes I had created. So I had an object to send certain API requests and likewise a set of objects to hold the response back as an object so I could utilize that 3rd party API. Then someone came to me and said why not just use the wsdl and a web service. Ok, so today I went and created a "Service Reference". I see that this is what's called a "Proxy Class". You just instantiate an instance of this and then walla you have access to all the methods from the wsdl. But this leaves me with auth questions. Back when I created my own classes manually, I had a class which exposed properties that I would set then access for things like signature, username, password that got sent along with the Http request that were required by whatever 3rd party API I was using to make API calls. But then with using a Service Reference, how then would I pass this information just like I had done in my custom classes? For instance I'm going to be working with the PayPal API. It requires you to send a signature and a few other pieces of information like username and password. // Determins if API call needs to use a session based URI string requestURI = UseAuthURI == true ? _requestURIAuthBased + aSessionID : _requestURI; byte[] data = XmlUtil.DocumentToBytes(doc); // Create the atual Request instance HttpWebRequest request = CreateWebRequest(requestURI, data.Length); So how do I pass username, password, signature, etc. when using web service references for each method call? Is it as simple as specifying it as a param to the method or do you use the .Credentials and .URL methods of your proxy class object? It seems to me Credentials means windows credentials but I could be wrong. Is it limited to that or can you use that to specify those required header values that PayPal expects with each method call/API request?

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  • Getting error "Association references unmapped class" when using interfaces in model

    - by Bjarke
    I'm trying to use the automap functionality in fluent to generate a DDL for the following model and program, but somehow I keep getting the error "Association references unmapped class: IRole" when I call the GenerateSchemaCreationScript method in NHibernate. When I replace the type of the ILists with the implementation of the interfaces (User and Role) everything works fine. What am I doing wrong here? How can I make fluent use the implemented versions of IUser and IRole as defined in Unity? public interface IRole { string Title { get; set; } IList<IUser> Users { get; set; } } public interface IUser { string Email { get; set; } IList<IRole> Roles { get; set; } } public class Role : IRole { public virtual string Title { get; set; } public virtual IList<IUser> Users { get; set; } } public class User : IUser { public virtual string Email { get; set; } public virtual IList<IRole> Roles { get; set; } } I use the following program to generate the DDL using the GenerateSchemaCreationScript in NHibernate: class Program { static void Main(string[] args) { var ddl = new NHibernateSessionManager(); ddl.BuildConfiguration(); } } public class NHibernateSessionManager { private ISessionFactory _sessionFactory; private static IUnityContainer _container; private static void InitContainer() { _container = new UnityContainer(); _container.RegisterType(typeof(IUser), typeof(User)); _container.RegisterType(typeof(IRole), typeof(Role)); } public ISessionFactory BuildConfiguration() { InitContainer(); return Fluently.Configure().Database(MsSqlConfiguration.MsSql2008 .ConnectionString("ConnectionString")) .Mappings(m => m.AutoMappings.Add( AutoMap.AssemblyOf<IUser>())) .ExposeConfiguration(BuildSchema) .BuildSessionFactory(); } private void BuildSchema(Configuration cfg) { var ddl = cfg.GenerateSchemaCreationScript(new NHibernate.Dialect.MsSql2008Dialect()); System.IO.File.WriteAllLines("Filename", ddl); } }

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  • Azure git deployment - missing references in 2nd assembly

    - by Dan
    I'm trying to setup Bitbucket deployment to an Azure website. I successfully have Bitbucket and Azure linked, but when I push to Bitbucket, I get the following error on the Azure site: If I click on 'View Log', it shows the following compile errors: D:\Windows\Microsoft.NET\Framework\v4.0.30319\Microsoft.Common.targets(1578,5): warning MSB3245: Could not resolve this reference. Could not locate the assembly "System.Web.Mvc, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35, processorArchitecture=MSIL". Check to make sure the assembly exists on disk. If this reference is required by your code, you may get compilation errors. [C:\DWASFiles\Sites\<projname>\VirtualDirectory0\site\repository\<projname>.Common\<projname>.Common.csproj] D:\Windows\Microsoft.NET\Framework\v4.0.30319\Microsoft.Common.targets(1578,5): warning MSB3245: Could not resolve this reference. Could not locate the assembly "WebMatrix.WebData, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35, processorArchitecture=MSIL". Check to make sure the assembly exists on disk. If this reference is required by your code, you may get compilation errors. [C:\DWASFiles\Sites\<projname>\VirtualDirectory0\site\repository\<projname>.Common\<projname>.Common.csproj] CustomMembershipProvider.cs(5,7): error CS0246: The type or namespace name 'WebMatrix' could not be found (are you missing a using directive or an assembly reference?) [C:\DWASFiles\Sites\<projname>\VirtualDirectory0\site\repository\<projname>.Common\<projname>.Common.csproj] CustomMembershipProvider.cs(9,38): error CS0246: The type or namespace name 'ExtendedMembershipProvider' could not be found (are you missing a using directive or an assembly reference?) [C:\DWASFiles\Sites\<projname>\VirtualDirectory0\site\repository\<projname>.Common\<projname>.Common.csproj] Models\AccountModels.cs(3,18): error CS0234: The type or namespace name 'Mvc' does not exist in the namespace 'System.Web' (are you missing an assembly reference?) [C:\DWASFiles\Sites\<projname>\VirtualDirectory0\site\repository\<projname>.Common\<projname>.Common.csproj] CustomMembershipProvider.cs(198,37): error CS0246: The type or namespace name 'OAuthAccountData' could not be found (are you missing a using directive or an assembly reference?) [C:\DWASFiles\Sites\<projname>\VirtualDirectory0\site\repository\<projname>.Common\<projname>.Common.csproj] Models\AccountModels.cs(40,10): error CS0246: The type or namespace name 'Compare' could not be found (are you missing a using directive or an assembly reference?) [C:\DWASFiles\Sites\<projname>\VirtualDirectory0\site\repository\<projname>.Common\<projname>.Common.csproj] Models\AccountModels.cs(40,10): error CS0246: The type or namespace name 'CompareAttribute' could not be found (are you missing a using directive or an assembly reference?) [C:\DWASFiles\Sites\<projname>\VirtualDirectory0\site\repository\<projname>.Common\<projname>.Common.csproj] Models\AccountModels.cs(73,10): error CS0246: The type or namespace name 'Compare' could not be found (are you missing a using directive or an assembly reference?) [C:\DWASFiles\Sites\<projname>\VirtualDirectory0\site\repository\<projname>.Common\<projname>.Common.csproj] Models\AccountModels.cs(73,10): error CS0246: The type or namespace name 'CompareAttribute' could not be found (are you missing a using directive or an assembly reference?) [C:\DWASFiles\Sites\<projname>\VirtualDirectory0\site\repository\<projname>.Common\<projname>.Common.csproj] Note that these compile errors are against another assembly in my project (the assembly where I put the business logic). When Googling, the only mention I found was about having to set the "local copy" flag to true for those references. I've tried this, but still got the same errors. This all compiles fine locally. Any ideas?

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  • C# Implementing a custom stream writer-esque class

    - by Luke
    How would I go about writing my own stream manipulator class? Basically what I'm trying to wrap my head around is storing the reference to the underlying stream in the writer. For example, when writing to a memory stream using a StreamWriter, when a Write() is made, the underlying memory stream is written to. Can I store the reference to an underlying stream without using pointers or unsafe code? Even if it was just a string I wanted to "write" to. Really this has little to do with stream writers, and I'm just wondering how I could store references in a class. The StreamWriter was the best example I could come up with for this.

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  • Why is Visual Studio 2008 stuck in debug mode when compiling

    - by Mark
    I have a .NET project that for some reason gets stuck in debug mode. I've changed the compile mode from debug to release in the toolbar, but my project ends up in the debug directory anyway. Seems like VS is not updating the SLN file or something. Please help! The reason I am asking about this is because it seems that there are weak references "ENCList" clogging up memory when my program runs, and they seem to be created when .NET apps are compiled in debug (or so says other sources I've found online). -Mark

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  • Maven: Unresolved references to [org.osgi.service.http]

    - by Simone Vellei
    I'm trying to create a bundle using HttpService for register Servlet using maven-bundle-plugin. The pom.xml of the project is: <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>felix-tutorial</groupId> <artifactId>example-1</artifactId> <version>1.0</version> <packaging>bundle</packaging> <name>Apache Felix Tutorial Example 1</name> <description>Apache Felix Tutorial Example 1</description> <!-- Build Configuration --> <build> <plugins> <plugin> <groupId>org.apache.felix</groupId> <artifactId>maven-bundle-plugin</artifactId> <extensions>true</extensions> <configuration> <instructions> <Bundle-SymbolicName>${pom.groupId}.${pom.artifactId}</Bundle-SymbolicName> <Bundle-Name>Service listener example</Bundle-Name> <Bundle-Description>A bundle that displays messages at startup and when service events occur</Bundle-Description> <Bundle-Vendor>Apache Felix</Bundle-Vendor> <Bundle-Version>1.0.0</Bundle-Version> <Bundle-Activator>tutorial.example1.Activator</Bundle-Activator> <Import-Package>org.osgi.framework;version="1.0.0", javax.servlet, javax.servlet.http</Import-Package> </instructions> </configuration> </plugin> </plugins> </build> <!-- Dependecies Management --> <dependencies> <dependency> <groupId>org.apache.felix</groupId> <artifactId>org.apache.felix.framework</artifactId> <version>2.0.4</version> </dependency> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.8.1</version> <scope>test</scope> </dependency> <dependency> <groupId>org.apache.felix</groupId> <artifactId>org.apache.felix.http.api</artifactId> <version>2.0.4</version> </dependency> <dependency> <groupId>org.apache.felix</groupId> <artifactId>org.apache.felix.http.base</artifactId> <version>2.0.4</version> </dependency> <dependency> <groupId>org.apache.felix</groupId> <artifactId>org.apache.felix.http.bridge</artifactId> <version>2.0.4</version> </dependency> <dependency> <groupId>org.apache.felix</groupId> <artifactId>org.apache.felix.http.bundle</artifactId> <version>2.0.4</version> </dependency> <dependency> <groupId>org.apache.felix</groupId> <artifactId>org.apache.felix.http.proxy</artifactId> <version>2.0.4</version> </dependency> <dependency> <groupId>org.apache.felix</groupId> <artifactId>org.apache.felix.http.whiteboard</artifactId> <version>2.0.4</version> </dependency> <dependency> <groupId>org.osgi</groupId> <artifactId>osgi_R4_compendium</artifactId> <version>1.0</version> </dependency> </dependencies> </project> "mvn install" command returns the following error: [INFO] Scanning for projects... [INFO] ------------------------------------------------------------------------ [INFO] Building Apache Felix Tutorial Example 1 [INFO] task-segment: [install] [INFO] ------------------------------------------------------------------------ Downloading: http://repo1.maven.org/maven2/org/apache/maven/plugins/maven-resources-plugin/2.3/maven-resources-plugin-2.3.pom Downloading: http://repo1.maven.org/maven2/org/apache/maven/plugins/maven-resources-plugin/2.3/maven-resources-plugin-2.3.jar Downloading: http://repo1.maven.org/maven2/org/apache/maven/plugins/maven-install-plugin/2.2/maven-install-plugin-2.2.pom Downloading: http://repo1.maven.org/maven2/org/apache/maven/plugins/maven-install-plugin/2.2/maven-install-plugin-2.2.jar Downloading: http://repo1.maven.org/maven2/org/apache/maven/shared/maven-filtering/1.0-beta-2/maven-filtering-1.0-beta-2.pom Downloading: http://repo1.maven.org/maven2/org/codehaus/plexus/plexus-interpolation/1.6/plexus-interpolation-1.6.pom Downloading: http://repo1.maven.org/maven2/org/codehaus/plexus/plexus-interpolation/1.6/plexus-interpolation-1.6.jar Downloading: http://repo1.maven.org/maven2/org/apache/maven/shared/maven-filtering/1.0-beta-2/maven-filtering-1.0-beta-2.jar [INFO] [resources:resources {execution: default-resources}] [WARNING] Using platform encoding (Cp1252 actually) to copy filtered resources, i.e. build is platform dependent! [INFO] skip non existing resourceDirectory C:\eclipse\ws\stripes-bundle\src\main\resources [INFO] [compiler:compile {execution: default-compile}] [INFO] Nothing to compile - all classes are up to date [INFO] [resources:testResources {execution: default-testResources}] [WARNING] Using platform encoding (Cp1252 actually) to copy filtered resources, i.e. build is platform dependent! [INFO] skip non existing resourceDirectory C:\eclipse\ws\stripes-bundle\src\test\resources [INFO] [compiler:testCompile {execution: default-testCompile}] [INFO] Nothing to compile - all classes are up to date [INFO] [surefire:test {execution: default-test}] [INFO] Surefire report directory: C:\eclipse\ws\stripes-bundle\target\surefire-reports ------------------------------------------------------- T E S T S ------------------------------------------------------- Running com.beanopoly.stripes.AppTest Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.031 sec Results : Tests run: 1, Failures: 0, Errors: 0, Skipped: 0 [INFO] [bundle:bundle {execution: default-bundle}] [ERROR] Error building bundle felix-tutorial:example-1:bundle:1.0 : Unresolved references to [org.osgi.service.http] by class(es) on the Bundle-Classpath[Jar:do [ERROR] Error(s) found in bundle configuration [INFO] ------------------------------------------------------------------------ [ERROR] BUILD ERROR [INFO] ------------------------------------------------------------------------ [INFO] Error(s) found in bundle configuration [INFO] ------------------------------------------------------------------------ [INFO] For more information, run Maven with the -e switch [INFO] ------------------------------------------------------------------------ [INFO] Total time: 12 seconds [INFO] Finished at: Sat Mar 27 13:11:47 CET 2010 [INFO] Final Memory: 12M/21M [INFO] ------------------------------------------------------------------------

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  • Visual Studio autoclean?

    - by kubal5003
    Hello, I have a solution with multiple projects - executable, library, and others(unimportant right now). Library contains EF entity classes and executable uses them. When I'm working on some code from the executable then every entity that I use is marked as an error and compiler says that I should check usings and references. Reference in the executable project is set to library project(not the dll itself). When I build the library project then everything gets back to normal, but when I start typing then it happens again. I could live with it, but intelli sense isn't working and that is quite a disadvantage. Any ideas?

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  • How does the Garbage Collector decide when to kill objects held by WeakReferences?

    - by Kennet Belenky
    I have an object, which I believe is held only by a WeakReference. I've traced its reference holders using SOS and SOSEX, and both confirm that this is the case (I'm not an SOS expert, so I could be wrong on this point). The standard explanation of WeakReferences is that the GC ignores them when doing its sweeps. Nonetheless, my object survives an invocation to GC.Collect(GC.MaxGeneration, GCCollectionMode.Forced). Is it possible for an object that is only referenced with a WeakReference to survive that collection? Is there an even more thorough collection that I can force? Or, should I re-visit my belief that the only references to the object are weak?

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  • .Net installation issue with SqlServerPipelineHost and SqlServer.DtsMsg

    - by Melody Friedenthal
    I added a web service consumer to a vb 2005 Windows app and tried to install it on another computer, which had an earlier version already installed (ClickOnce deployment). An error came up saying I needed to install Microsoft.SqlServer.PipelineHist in the GAC. I added PipelineHost to the list of references and marked it Copy Local = true, rebuilt the solution, published it and tried to install it on that other computer. This time it said I needed to install Microsoft.SqlServer.DtsMsg, however, that component does not show up on my list of .Net components. Where do I go from here? Thank you.

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  • Visual Studio 2008 Explicit Reference Error

    - by Alan
    I have a project which references a dll in the same solution (called "Common"). Common has two types of errors with the same names but different namespaces i.e. Common.Login.UserDeleted Common.Imaging.UserDeleted When I type UserDeleted visual studio recognizes both of these and asks for which it is ("ambiguous reference"). I right-click UserDeleted and select one of the two above, yet it then says that the type or reference doesn't exist! It doesn't make any sense. Why is this happening? I can't compile my program until I find a solution to this, thanks

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  • Automapping to EntityKeys in Entity Framework

    - by CodeGrue
    Does anyone have a technique to automap (using Automapper) references to child entities. So say I have a ViewModel: class AddressModel { int Id; string Street; StateModel State; } class StateModel { int Id; string Name; } And I pass this into a repository to map to equivalent entities in Entity Framework. When Automapping, I want it to automap AddressModel.State.ID to the EntityKey of AddressEntity.StateReference. So hand crafted code would look like this: addressEntity.Id = AddressModel.Id; addressEntity.Street = AddressModel.Street addressEntity.StateReference.EntityKey = new EntityKey("MyDB.States", "Id", AddressModel.State.Id); Obviously, when automapper tries to assign an Address.State.Id to the equivalent in EF, an exception is thrown.

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  • Check if row already exists, if so tell the referenced table the id

    - by flhe
    Let's assume I have a table magazine: CREATE TABLE magazine ( magazine_id integer NOT NULL DEFAULT nextval(('public.magazine_magazine_id_seq'::text)::regclass), longname character varying(1000), shortname character varying(200), issn character varying(9), CONSTRAINT pk_magazine PRIMARY KEY (magazine_id) ); And another table issue: CREATE TABLE issue ( issue_id integer NOT NULL DEFAULT nextval(('public.issue_issue_id_seq'::text)::regclass), number integer, year integer, volume integer, fk_magazine_id integer, CONSTRAINT pk_issue PRIMARY KEY (issue_id), CONSTRAINT fk_magazine_id FOREIGN KEY (fk_magazine_id) REFERENCES magazine (magazine_id) MATCH SIMPLE ON UPDATE NO ACTION ON DELETE NO ACTION ); Current INSERTS: INSERT INTO magazine (longname,shotname,issn) VALUES ('a long name','ee','1111-2222'); INSERT INTO issue (fk_magazine_id,number,year,volume) VALUES (currval('magazine_magazine_id_seq'),'8','1982','6'); Now a row should only be inserted into 'magazine', if it does not already exist. However if it exists, the table 'issue' needs to get the 'magazine_id' of the row that already exists in order to establish the reference. How can i do this? Thx in advance!

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  • DB Design - Linking to a parent without circular reference issues

    - by zSysop
    Hi all, I'm having trouble coming up with a solution for the following issue. Lets say i have a db that looks something like the following: Issue Table Id | Details | CreateDate | ClosedDate Issue Notes Table Id | ObjectId | Notes | NoteDate Issue Assignment Table Id | ObjectId | AssignedToId| AssignedDate I'd like allow the linking of an issue to another issue. I thought about adding a column to the Issue table called ParentIssueId and that would allow me the ability to link issues, but i foresee circular references occurring within the issue table if i go through with this implementation. Is there a better way to go about doing this, and if so, how? Thanks

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  • Alternates to C++ Reference/Pointer Syntax

    - by Jon Purdy
    What languages other than C and C++ have explicit reference and pointer type qualifiers? People seem to be easily confused by the right-to-left reading order of types, where char*& is "a reference to a pointer to a character", or a "character-pointer reference"; do any languages with explicit references make use of a left-to-right reading order, such as &*char/ref ptr char? I'm working on a little language project, and legibility is one of my key concerns. It seems to me that this is one of those questions to which it's easy for a person but hard for a search engine to provide an answer. Thanks in advance!

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  • Alternatives to C++ Reference/Pointer Syntax

    - by Jon Purdy
    What languages other than C and C++ have explicit reference and pointer type qualifiers? People seem to be easily confused by the right-to-left reading order of types, where char*& is "a reference to a pointer to a character", or a "character-pointer reference"; do any languages with explicit references make use of a left-to-right reading order, such as &*char/ref ptr char? I'm working on a little language project, and legibility is one of my key concerns. It seems to me that this is one of those questions to which it's easy for a person but hard for a search engine to provide an answer. Thanks in advance!

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  • does class/object models have a out-of-the-box equivalent to a database foreign key constraint

    - by Greg
    Hi, Does does class/object models have a out-of-the-box equivalent to a database foreign key constraint? Assume the language is C# please. That is say Class A has a field that references Class B and vica-versa. If I have Object A & B (instantiated from these classes) what happens if I delete Object B? Does it auto-delete or throw a constraint issue if it still exists in Object A as a reference? That is, for this scenario is there a way to ensure when a Object A is delete that either (a) object B is delete like a cascade delete, or (b) a constraint exception is thrown as the expectation is that the reference in Class B should be non-null?

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  • Purely functional equivalent of weakhashmap?

    - by Jon Harrop
    Weak hash tables like Java's weak hash map use weak references to track the collection of unreachable keys by the garbage collector and remove bindings with that key from the collection. Weak hash tables are typically used to implement indirections from one vertex or edge in a graph to another because they allow the garbage collector to collect unreachable portions of the graph. Is there a purely functional equivalent of this data structure? If not, how might one be created? This seems like an interesting challenge. The internal implementation cannot be pure because it must collect (i.e. mutate) the data structure in order to remove unreachable parts but I believe it could present a pure interface to the user, who could never observe the impurities because they only affect portions of the data structure that the user can, by definition, no longer reach.

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