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  • Hierarchy as grid

    - by seesharp
    I have hierarchy: public class Parameter { public string Name { get; set; } public Value Value { get; set; } } public abstract class Value { } public class StringValue : Value { public string Str { get; set; } } public class ComplexValue : Value { public ComplexValue() { Parameters = new List<Parameter>(); } public List<Parameter> Parameters { get; set; } } /// Contains ComplexValue public class ComplexParameter : Parameter { } And XAML with templates <Window.Resources> <DataTemplate DataType="{x:Type pc:Parameter}"> <Grid> <Grid.ColumnDefinitions> <ColumnDefinition/> <ColumnDefinition/> </Grid.ColumnDefinitions> <Label Grid.Column="0" Content="{Binding Name}"/> <ContentPresenter Grid.Column="1" Content="{Binding Value}"/> </Grid> </DataTemplate> <DataTemplate DataType="{x:Type pc:ComplexParameter}"> <StackPanel> <Label Content="{Binding Name}"/> <ContentControl Margin="18,0,0,0" Content="{Binding Value}"/> </StackPanel> </DataTemplate> <DataTemplate DataType="{x:Type pc:ComplexValue}"> <ItemsControl ItemsSource="{Binding Parameters}"/> </DataTemplate> <DataTemplate DataType="{x:Type pc:StringValue}"> <TextBox Text="{Binding Str}"/> </DataTemplate> </Window.Resources> This look like: Param1 -Control---- Param2 -Control---- Complex1 Sub Param1 -Control- Sub Param2 -Control- Or image here: freeimagehosting.net/uploads/9d438f52e7.png Question How to do indent only in left column (parameter names). Something like this: Param1 -Control---- Param2 -Control---- Complex1 Sub Param1 -Control---- Sub Param2 -Control---- Or image here: freeimagehosting.net/uploads/4ab3045b75.png

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  • Overwhelmed by design patterns... where to begin?

    - by Pete
    I am writing a simple prototype code to demonstrate & profile I/O schemes (HDF4, HDF5, HDF5 using parallel IO, NetCDF, etc.) for a physics code. Since focus is on IO, the rest of the program is very simple: class Grid { public: floatArray x,y,z; }; class MyModel { public: MyModel(const int &nip1, const int &njp1, const int &nkp1, const int &numProcs); Grid grid; map<string, floatArray> plasmaVariables; }; Where floatArray is a simple class that lets me define arbitrary dimensioned arrays and do mathematical operations on them (i.e. x+y is point-wise addition). Of course, I could use better encapsulation (write accessors/setters, etc.), but that's not the concept I'm struggling with. For the I/O routines, I am envisioning applying simple inheritance: Abstract I/O class defines read & write functions to fill in the "myModel" object HDF4 derived class HDF5 HDF5 using parallel IO NetCDF etc... The code should read data in any of these formats, then write out to any of these formats. In the past, I would add an AbstractIO member to myModel and create/destroy this object depending on which I/O scheme I want. In this way, I could do something like: myModelObj.ioObj->read('input.hdf') myModelObj.ioObj->write('output.hdf') I have a bit of OOP experience but very little on the Design Patterns front, so I recently acquired the Gang of Four book "Design Patterns: Elements of Reusable Object-Oriented Software". OOP designers: Which pattern(s) would you recommend I use to integrate I/O with the myModel object? I am interested in answering this for two reasons: To learn more about design patterns in general Apply what I learn to help refactor an large old crufty/legacy physics code to be more human-readable & extensible. I am leaning towards applying the Decerator pattern to myModel, so I can attach the I/O responsibilities dynamically to myModel (i.e. whether to use HDF4, HDF5, etc.). However, I don't feel very confident that this is the best pattern to apply. Reading the Gang of Four book cover-to-cover before I start coding feels like a good way to develop an unhealthy caffeine addiction. What patterns do you recommend?

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  • c++ class member functions selected by traits

    - by Jive Dadson
    I am reluctant to say I can't figure this out, but I can't figure this out. I've googled and searched stackoverflow, and come up empty. The abstract, and possibly overly vague form of the question is, how can I use the traits-pattern to instantiate non-virtual member functions? The question came up while modernizing a set of multivariate function optimizers that I wrote more than 10 years ago. The optimizers all operate by selecting a straight-line path through the parameter space away from the current best point (the "update"), then finding a better point on that line (the "line search"), then testing for the "done" condition, and if not done, iterating. There are different methods for doing the update, the line-search, and conceivably for the done test, and other things. Mix and match. Different update formulae require different state-variable data. For example, the LMQN update requires a vector, and the BFGS update requires a matrix. If evaluating gradients is cheap, the line-search should do so. If not, it should use function evaluations only. Some methods require more accurate line-searches than others. Those are just some examples. The original version instatiates several of the combinations by means of virtual functions. Some traits are selected by setting mode bits. Yuck. It would be trivial to define the traits with #define's and the member functions with #ifdef's and macros. But that's so twenty years ago. It bugs me that I cannot figure out a whiz-bang modern way. If there were only one trait that varied, I could use the curiously recurring template pattern. But I see no way to extend that to arbitrary combinations of traits. I tried doing it using boost::enable_if, etc.. The specialized state info was easy. I managed to get the functions done, but only by resorting to non-friend external functions that have the this-pointer as a parameter. I never even figured out how to make the functions friends, much less member functions. Perhaps tag-dispatch is the key. I haven't gotten very deeply into that. Surely it's possible, right? If so, what is best practice?

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  • PHP 'instanceof' failing with class constant

    - by Nathan Loding
    I'm working on a framework that I'm trying to type as strongly as I possibly can. (I'm working within PHP and taking some of the ideas that I like from C# and trying to utilize them within this framework.) I'm creating a Collection class that is a collection of domain entities/objects. It's kinda modeled after the List<T> object in .Net. I've run into an obstacle that is preventing me from typing this class. If I have a UserCollection, it should only allow User objects into it. If I have a PostCollection, it should only allow Post objects. All Collections in this framework need to have certain basic functions, such as add, remove, iterate. I created an interface, but found that I couldn't do the following: interface ICollection { public function add($obj) } class PostCollection implements ICollection { public function add(Post $obj) {} } This broke it's compliance with the interface. But I can't have the interface strongly typed because then all Collections are of the same type. So I attempted the following: interface ICollection { public function add($obj) } abstract class Collection implements ICollection { const type = 'null'; } class PostCollection { const type = 'Post'; public function add($obj) { if(!($obj instanceof self::type)) { throw new UhOhException(); } } } When I attempt to run this code, I get syntax error, unexpected T_STRING, expecting T_VARIABLE or '$' on the instanceof statement. A little research into the issue and it looks like the root of the cause is that $obj instanceof self is valid to test against the class. It appears that PHP doesn't process the entire self::type constant statement in the expression. Adding parentheses around the self::type variable threw an error regarding an unexpected '('. An obvious workaround is to not make the type variable a constant. The expression $obj instanceof $this->type works just fine (if $type is declared as a variable, of course). I'm hoping that there's a way to avoid that, as I'd like to define the value as a constant to avoid any possible change in the variable later. Any thoughts on how I can achieve this, or have I take PHP to it's limit in this regard? Is there a way of "escaping" or encapsulating self::this so that PHP won't die when processing it?

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  • How can I implement NotOfType<T> in LINQ that has a nice calling syntax?

    - by Lette
    I'm trying to come up with an implementation for NotOfType, which has a readable call syntax. NotOfType should be the complement to OfType<T> and would consequently yield all elements that are not of type T My goal was to implement a method which would be called just like OfType<T>, like in the last line of this snippet: public abstract class Animal {} public class Monkey : Animal {} public class Giraffe : Animal {} public class Lion : Animal {} var monkey = new Monkey(); var giraffe = new Giraffe(); var lion = new Lion(); IEnumerable<Animal> animals = new Animal[] { monkey, giraffe, lion }; IEnumerable<Animal> fewerAnimals = animals.NotOfType<Giraffe>(); However, I can not come up with an implementation that supports that specific calling syntax. This is what I've tried so far: public static class EnumerableExtensions { public static IEnumerable<T> NotOfType<T>(this IEnumerable<T> sequence, Type type) { return sequence.Where(x => x.GetType() != type); } public static IEnumerable<T> NotOfType<T, TExclude>(this IEnumerable<T> sequence) { return sequence.Where(x => !(x is TExclude)); } } Calling these methods would look like this: // Animal is inferred IEnumerable<Animal> fewerAnimals = animals.NotOfType(typeof(Giraffe)); and // Not all types could be inferred, so I have to state all types explicitly IEnumerable<Animal> fewerAnimals = animals.NotOfType<Animal, Giraffe>(); I think that there are major drawbacks with the style of both of these calls. The first one suffers from a redundant "of type/type of" construct, and the second one just doesn't make sense (do I want a list of animals that are neither Animals nor Giraffes?). So, is there a way to accomplish what I want? If not, could it be possible in future versions of the language? (I'm thinking that maybe one day we will have named type arguments, or that we only need to explicitly supply type arguments that can't be inferred?) Or am I just being silly?

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  • Why is javac 1.5 running so slowly compared with the Eclipse compiler?

    - by Simon Nickerson
    I have a Java Maven project with about 800 source files (some generated by javacc/JTB) which is taking a good 25 minutes to compile with javac. When I changed my pom.xml over to use the Eclipse compiler, it takes about 30 seconds to compile. Any suggestions as to why javac (1.5) is running so slowly? (I don't want to switch over to the Eclipse compiler permanently, as the plugin for Maven seems more than a little buggy.) I have a test case which easily reproduces the problem. The following code generates a number of source files in the default package. If you try to compile ImplementingClass.java with javac, it will seem to pause for an inordinately long time. import java.io.File; import java.io.FileNotFoundException; import java.io.PrintStream; public class CodeGenerator { private final static String PATH = System.getProperty("java.io.tmpdir"); private final static int NUM_TYPES = 1000; public static void main(String[] args) throws FileNotFoundException { PrintStream interfacePs = new PrintStream(PATH + File.separator + "Interface.java"); PrintStream abstractClassPs = new PrintStream(PATH + File.separator + "AbstractClass.java"); PrintStream implementingClassPs = new PrintStream(PATH + File.separator + "ImplementingClass.java"); interfacePs.println("public interface Interface<T> {"); abstractClassPs.println("public abstract class AbstractClass<T> implements Interface<T> {"); implementingClassPs.println("public class ImplementingClass extends AbstractClass<Object> {"); for (int i=0; i<NUM_TYPES; i++) { String nodeName = "Node" + i; PrintStream nodePs = new PrintStream(PATH + File.separator + nodeName + ".java"); nodePs.printf("public class %s { }\n", nodeName); nodePs.close(); interfacePs.printf("void visit(%s node, T obj);%n", nodeName); abstractClassPs.printf("public void visit(%s node, T obj) { System.out.println(obj.toString()); }%n", nodeName); } interfacePs.println("}"); abstractClassPs.println("}"); implementingClassPs.println("}"); interfacePs.close(); abstractClassPs.close(); implementingClassPs.close(); } }

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  • NHibernate unintentional lazy property loading

    - by chiccodoro
    I introduced a mapping for a business object which has (among others) a property called "Name": public class Foo : BusinessObjectBase { ... public virtual string Name { get; set; } } For some reason, when I fetch "Foo" objects, NHibernate seems to apply lazy property loading (for simple properties, not associations): The following code piece generates n+1 SQL statements, whereof the first only fetches the ids, and the remaining n fetch the Name for each record: ISession session = ...IQuery query = session.CreateQuery(queryString); ITransaction tx = session.BeginTransaction(); List<Foo> result = new List<Foo>(); foreach (Foo foo in query.Enumerable()) { result.Add(foo); } tx.Commit(); session.Close(); produces: NHibernate: select foo0_.FOO_ID as col_0_0_ from V1_FOO foo0_<br/> NHibernate: SELECT foo0_.FOO_ID as FOO1_2_0_, foo0_.NAME as NAME2_0_ FROM V1_FOO foo0_ WHERE foo0_.FOO_ID=:p0;:p0 = 81<br/> NHibernate: SELECT foo0_.FOO_ID as FOO1_2_0_, foo0_.NAME as NAME2_0_ FROM V1_FOO foo0_ WHERE foo0_.FOO_ID=:p0;:p0 = 36470<br/> NHibernate: SELECT foo0_.FOO_ID as FOO1_2_0_, foo0_.NAME as NAME2_0_ FROM V1_FOO foo0_ WHERE foo0_.FOO_ID=:p0;:p0 = 36473 Similarly, the following code leads to a LazyLoadingException after session is closed: ISession session = ... ITransaction tx = session.BeginTransaction(); Foo result = session.Load<Foo>(id); tx.Commit(); session.Close(); Console.WriteLine(result.Name); Following this post, "lazy properties ... is rarely an important feature to enable ... (and) in Hibernate 3, is disabled by default." So what am I doing wrong? I managed to work around the LazyLoadingException by doing a NHibernateUtil.Initialize(foo) but the even worse part are the n+1 sql statements which bring my application to its knees. This is how the mapping looks like: <class name="Foo" table="V1_FOO"> ... <property name="Name" column="NAME"/> </class> BTW: The abstract "BusinessObjectBase" base class encapsulates the ID property which serves as the internal identifier.

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  • Unresolved External Symbol linker error (C++)

    - by Niranjan
    Hi, I am trying to develop abstract design pattern code for one of my project as below.. But, I am not able to compile the code ..giving some compile errors(like "unresolved external symbol "public: virtual void __thiscall Xsecs::draw_lines(double,double)" (?draw_lines@Xsecs@@UAEXNN@Z)" ).. Can any one please help me out in this... #include "stdafx.h" #include <iostream> #include <vector> #include "Xsecs.h" using namespace std; //Product class class Xsecs { public: virtual void draw_lines(double pt1, double pt2); virtual void draw_curves(double pt1, double rad); }; class polyline: public Xsecs { public: virtual void draw_lines(double pt1,double pt2) { cout<<"draw_line in polygon"<<endl; } virtual void draw_curves(double pt1, double rad) { cout<<"Draw_curve in circle"<<endl; } /*void create_polygons() { cout<<"create_polygon_thru_draw_lines"<<endl; }*/ }; class circle: public Xsecs { public: virtual void draw_lines(double pt1,double pt2) { cout<<"draw_line in polygon"<<endl; } virtual void draw_curves(double pt1, double rad) { cout<<"Draw_curve in circle"<<endl; } /*void create_circles() { cout<<"Create circle"<<endl; }*/ }; //Factory class class Factory { public: virtual polyline* create_polyline()=0; virtual circle* create_circle()=0; }; class Factory1: public Factory { public: polyline* create_polyline() { return new polyline(); } circle* create_circle() { return new circle(); } }; class Factory2: public Factory { public: circle* create_circle() { return new circle(); } polyline* create_polyline() { return new polyline(); } }; int _tmain(int argc, _TCHAR* argv[]) { Factory1 f1; Factory * fp=&f1; return 0; }

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  • Persistent (purely functional) Red-Black trees on disk performance

    - by Waneck
    I'm studying the best data structures to implement a simple open-source object temporal database, and currently I'm very fond of using Persistent Red-Black trees to do it. My main reasons for using persistent data structures is first of all to minimize the use of locks, so the database can be as parallel as possible. Also it will be easier to implement ACID transactions and even being able to abstract the database to work in parallel on a cluster of some kind. The great thing of this approach is that it makes possible implementing temporal databases almost for free. And this is something quite nice to have, specially for web and for data analysis (e.g. trends). All of this is very cool, but I'm a little suspicious about the overall performance of using a persistent data structure on disk. Even though there are some very fast disks available today, and all writes can be done asynchronously, so a response is always immediate, I don't want to build all application under a false premise, only to realize it isn't really a good way to do it. Here's my line of thought: - Since all writes are done asynchronously, and using a persistent data structure will enable not to invalidate the previous - and currently valid - structure, the write time isn't really a bottleneck. - There are some literature on structures like this that are exactly for disk usage. But it seems to me that these techniques will add more read overhead to achieve faster writes. But I think that exactly the opposite is preferable. Also many of these techniques really do end up with a multi-versioned trees, but they aren't strictly immutable, which is something very crucial to justify the persistent overhead. - I know there still will have to be some kind of locking when appending values to the database, and I also know there should be a good garbage collecting logic if not all versions are to be maintained (otherwise the file size will surely rise dramatically). Also a delta compression system could be thought about. - Of all search trees structures, I really think Red-Blacks are the most close to what I need, since they offer the least number of rotations. But there are some possible pitfalls along the way: - Asynchronous writes -could- affect applications that need the data in real time. But I don't think that is the case with web applications, most of the time. Also when real-time data is needed, another solutions could be devised, like a check-in/check-out system of specific data that will need to be worked on a more real-time manner. - Also they could lead to some commit conflicts, though I fail to think of a good example of when it could happen. Also commit conflicts can occur in normal RDBMS, if two threads are working with the same data, right? - The overhead of having an immutable interface like this will grow exponentially and everything is doomed to fail soon, so this all is a bad idea. Any thoughts? Thanks! edit: There seems to be a misunderstanding of what a persistent data structure is: http://en.wikipedia.org/wiki/Persistent_data_structure

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  • Creating AST for shared and local variables

    - by Rizwan Abbasi
    Here is my grammar grammar simulator; options { language = Java; output = AST; ASTLabelType=CommonTree; } //imaginary tokens tokens{ SHARED; LOCALS; BOOL; RANGE; ARRAY; } parse : declaration+ ; declaration :variables ; variables : locals ; locals : (bool | range | array) ; bool :ID 'in' '[' ID ',' ID ']' ('init' ID)? -> ^(BOOL ID ID ID ID?) ; range : ID 'in' '[' INT '..' INT ']' ('init' INT)? -> ^(RANGE ID INT INT INT?) ; array :ID 'in' 'array' 'of' '[' INT '..' INT ']' ('init' INT)? -> ^(ARRAY ID INT INT INT?) ; ID : (('a'..'z' | 'A'..'Z'|'_')('a'..'z' | 'A'..'Z'|'0'..'9'|'_'))* ; INT : ('0'..'9')+ ; WHITESPACE : ('\t' | ' ' | '\r' | '\n' | '\u000C')+ {$channel = HIDDEN;} ; INPUT flag in [down, up] init down pc in [0..7] init 0 CA in array of [0..5] init 0 AST It is having a small problem. Variables (bool, range or array) can be of two abstract types 1. locals (each object will have it's own variable) 2. shared (think of static in java, same for all object) Now the requirements are changed. I want the user to input like this NEW INPUT domains: upDown [up,down] possibleStates [0-7] booleans [true,false] locals: pc in possibleStates init 0 flag in upDown init down flag1 in upDown init down map in array of booleans init false shared: pcs in possibleStates init 0 flag in upDown init down flag1 in upDown init down maps in array of booleans init false Again, all the variables can be of two types (of any domain sepecified) 1. Local 2. Shared In Domains: upDown [up,down] possibleStates [0-7] upDown, up, down and possibleStates are of type ID (ID is defined in my above grammar), 0 and 7 are of type INT Can any body help me how to convert my current grammar to meet new specifications.

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  • ActionResult - Service

    - by cem
    I bored, writing same code for service and ui. Then i tried to write a converter for simple actions. This converter, converting Service Results to MVC result, seems like good solution for me but anyway i think this gonna opposite MVC pattern. So here, I need help, what you think about algorithm - is this good or not? Thanks ServiceResult - Base: public abstract class ServiceResult { public static NoPermissionResult Permission() { return new NoPermissionResult(); } public static SuccessResult Success() { return new SuccessResult(); } public static SuccessResult<T> Success<T>(T result) { return new SuccessResult<T>(result); } protected ServiceResult(ServiceResultType serviceResultType) { _resultType = serviceResultType; } private readonly ServiceResultType _resultType; public ServiceResultType ResultType { get { return _resultType; } } } public class SuccessResult<T> : ServiceResult { public SuccessResult(T result) : base(ServiceResultType.Success) { _result = result; } private readonly T _result; public T Result { get { return _result; } } } public class SuccessResult : SuccessResult<object> { public SuccessResult() : this(null) { } public SuccessResult(object o) : base(o) { } } Service - eg. ForumService: public ServiceResult Delete(IVUser user, int id) { Forum forum = Repository.GetDelete(id); if (!Permission.CanDelete(user, forum)) { return ServiceResult.Permission(); } Repository.Delete(forum); return ServiceResult.Success(); } Controller: public class BaseController { public ActionResult GetResult(ServiceResult result) { switch (result.ResultType) { case ServiceResultType.Success: var successResult = (SuccessResult)result; return View(successResult.Result); break; case ServiceResultType.NoPermission: return View("Error"); break; default: return View(); break; } } } [HandleError] public class ForumsController : BaseController { [ValidateAntiForgeryToken] [Transaction] [AcceptVerbs(HttpVerbs.Post)] public ActionResult Delete(int id) { ServiceResult result = ForumService.Delete(WebUser.Current, id); /* Custom result */ if (result.ResultType == ServiceResultType.Success) { TempData[ControllerEnums.GlobalViewDataProperty.PageMessage.ToString()] = "The forum was successfully deleted."; return this.RedirectToAction(ec => Index()); } /* Custom result */ /* Execute Permission result etc. */ TempData[ControllerEnums.GlobalViewDataProperty.PageMessage.ToString()] = "A problem was encountered preventing the forum from being deleted. " + "Another item likely depends on this forum."; return GetResult(result); } }

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  • Can't destroy record in many-to-many relationship

    - by Dmart
    I'm new to Rails, so I'm sure I've made a simple mistake. I've set up a many-to-many relationship between two models: User and Group. They're connected through the junction model GroupMember. Here are my models (removed irrelevant stuff): class User < ActiveRecord::Base has_many :group_members has_many :groups, :through => :group_members end class GroupMember < ActiveRecord::Base belongs_to :group belongs_to :user end class Group < ActiveRecord::Base has_many :group_members has_many :users, :through => :group_members end The table for GroupMembers contains additional information about the relationship, so I didn't use has_and_belongs_to_many (as per the Rails "Active Record Associations" guide). The problem I'm having is that I can't destroy a GroupMember. Here's the output from rails console: irb(main):006:0> m = GroupMember.new => #<GroupMember group_id: nil, user_id: nil, active: nil, created_at: nil, updated_at: nil> irb(main):007:0> m.group_id =1 => 1 irb(main):008:0> m.user_id = 16 => 16 irb(main):009:0> m.save => true irb(main):010:0> m.destroy NoMethodError: undefined method `eq' for nil:NilClass from /usr/local/lib/ruby/gems/1.8/gems/activesupport-3.0.4/lib/active_support/whiny_nil.rb:48:in `method_missing' from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.4/lib/active_record/persistence.rb:79:in `destroy' from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.4/lib/active_record/locking/optimistic.rb:110:in `destroy' from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.4/lib/active_record/callbacks.rb:260:in `destroy' from /usr/local/lib/ruby/gems/1.8/gems/activesupport-3.0.4/lib/active_support/callbacks.rb:413:in `_run_destroy_callbacks' from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.4/lib/active_record/callbacks.rb:260:in `destroy' from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.4/lib/active_record/transactions.rb:235:in `destroy' from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.4/lib/active_record/transactions.rb:292:in `with_transaction_returning_status' from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.4/lib/active_record/connection_adapters/abstract/database_statements.rb:139:in `transaction' from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.4/lib/active_record/transactions.rb:207:in `transaction' from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.4/lib/active_record/transactions.rb:290:in `with_transaction_returning_status' from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.4/lib/active_record/transactions.rb:235:in `destroy' from (irb):10 This is driving me crazy, so any help would be greatly appreciated.

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  • Multi-tier applications using L2S, WCF and Base Class

    - by Gena Verdel
    Hi all. One day I decided to build this nice multi-tier application using L2S and WCF. The simplified model is : DataBase-L2S-Wrapper(DTO)-Client Application. The communication between Client and Database is achieved by using Data Transfer Objects which contain entity objects as their properties. abstract public class BaseObject { public virtual IccSystem.iccObjectTypes ObjectICC_Type { get { return IccSystem.iccObjectTypes.unknownType; } } [global::System.Data.Linq.Mapping.ColumnAttribute(Storage = "_ID", AutoSync = AutoSync.OnInsert, DbType = "BigInt NOT NULL IDENTITY", IsPrimaryKey = true, IsDbGenerated = true)] [global::System.Runtime.Serialization.DataMemberAttribute(Order = 1)] public virtual long ID { //get; //set; get { return _ID; } set { _ID = value; } } } [DataContract] public class BaseObjectWrapper<T> where T : BaseObject { #region Fields private T _DBObject; #endregion #region Properties [DataMember] public T Entity { get { return _DBObject; } set { _DBObject = value; } } #endregion } Pretty simple, isn't it?. Here's the catch. Each one of the mapped classes contains ID property itself so I decided to override it like this [global::System.Data.Linq.Mapping.TableAttribute(Name="dbo.Divisions")] [global::System.Runtime.Serialization.DataContractAttribute()] public partial class Division : INotifyPropertyChanging, INotifyPropertyChanged { [global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_ID", AutoSync=AutoSync.OnInsert, DbType="BigInt NOT NULL IDENTITY", IsPrimaryKey=true, IsDbGenerated=true)] [global::System.Runtime.Serialization.DataMemberAttribute(Order=1)] public override long ID { get { return this._ID; } set { if ((this._ID != value)) { this.OnIDChanging(value); this.SendPropertyChanging(); this._ID = value; this.SendPropertyChanged("ID"); this.OnIDChanged(); } } } } Wrapper for division is pretty straightforward as well: public class DivisionWrapper : BaseObjectWrapper<Division> { } It worked pretty well as long as I kept ID values at mapped class and its BaseObject class the same(that's not very good approach, I know, but still) but then this happened: private CentralDC _dc; public bool UpdateDivision(ref DivisionWrapper division) { DivisionWrapper tempWrapper = division; if (division.Entity == null) { return false; } try { Table<Division> table = _dc.Divisions; var q = table.Where(o => o.ID == tempWrapper.Entity.ID); if (q.Count() == 0) { division.Entity._errorMessage = "Unable to locate entity with id " + division.Entity.ID.ToString(); return false; } var realEntity = q.First(); realEntity = division.Entity; _dc.SubmitChanges(); return true; } catch (Exception ex) { division.Entity._errorMessage = ex.Message; return false; } } When trying to enumerate over the in-memory query the following exception occurred: Class member BaseObject.ID is unmapped. Although I'm stating the type and overriding the ID property L2S fails to work. Any suggestions?

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  • c++ compile error

    - by Niranjan
    Hi, I am trying to develop abstract design pattern code for one of my project as below.. But, I am not able to compile the code ..giving some compile errors(like "conversion from 'ProductA1 *' to 'ProductA *' exists, but is inaccessible" ).. Can any one please help me out in this... #include "stdafx.h" #include <iostream> using namespace std; class ProductA { public: virtual void Operation1()=0; virtual void Operation2()=0; }; class ProductA1 : ProductA { public: virtual void Operation1() {cout<<"PD ProductA1 Operation1"<<endl; } virtual void Operation2() {cout<<"PD ProductA1 Operation2"<<endl; } }; class ProductA2 : ProductA { public: virtual void Operation1() {cout<<"DT ProductA2 Operation1"<<endl; } virtual void Operation2() {cout<<"DT ProductA2 Operation2"<<endl; } }; //------------------------------------------------------------- class ProductB { public: virtual void Operation3()=0; virtual void Operation4()=0; }; class ProductB1 : ProductB { public: void Operation3() { cout<<"PD ProductB1 Operation3"<<endl; } void Operation4() { cout<<"PD ProductB1 Operation4"<<endl; } }; class ProductB2 : ProductB { public: void Operation3() { cout<<"DT ProductB2 Operation3"<<endl; } void Operation4() { cout<<"DT ProductB2 Operation4"<<endl; } }; //--------------- abstrct factory --------------------------- class Factory { public: virtual ProductA* CreateA () =0; virtual ProductB* CreateB ()=0; }; class Factory1 : Factory { public: ProductA* CreateA () { return new ProductA1(); } ProductB* CreateB () { return new ProductB1(); } }; class Factory2 : Factory { public: ProductA* CreateA () { return new ProductA2(); } ProductB* CreateB () { return new ProductB2(); } }; //--------------------- client -------------------------------- int _tmain(int argc, _TCHAR* argv[]) { Factory* pf = new Factory1(); ProductA *pa = pf->CreateA(); pa->Operation1(); pa->Operation2(); ProductB *pb = pf->CreateB(); pb->Operation3(); pb->Operation4(); return 0; }

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  • Help with method logic in Java, hw

    - by Crystal
    I have a Loan class that in its printPayment method, it prints the amortization table of a loan for a hw assignment. We are also to implement a print first payment method, and a print last payment method. Since my calculation is done in the printPayment method, I didn't know how I could get the value in the first or last iteration of the loop and print that amount out. One way I can think of is to write a new method that might return that value, but I wasn't sure if there was a better way. Here is my code: public abstract class Loan { public void setClient(Person client) { this.client = client; } public Person getClient() { return client; } public void setLoanId() { loanId = nextId; nextId++; } public int getLoanId() { return loanId; } public void setInterestRate(double interestRate) { this.interestRate = interestRate; } public double getInterestRate() { return interestRate; } public void setLoanLength(int loanLength) { this.loanLength = loanLength; } public int getLoanLength() { return loanLength; } public void setLoanAmount(double loanAmount) { this.loanAmount = loanAmount; } public double getLoanAmount() { return loanAmount; } public void printPayments() { double monthlyInterest; double monthlyPrincipalPaid; double newPrincipal; int paymentNumber = 1; double monthlyInterestRate = interestRate / 1200; double monthlyPayment = loanAmount * (monthlyInterestRate) / (1 - Math.pow((1 + monthlyInterestRate),( -1 * loanLength))); System.out.println("Payment Number | Interest | Principal | Loan Balance"); // amortization table while (loanAmount >= 0) { monthlyInterest = loanAmount * monthlyInterestRate; monthlyPrincipalPaid = monthlyPayment - monthlyInterest; newPrincipal = loanAmount - monthlyPrincipalPaid; loanAmount = newPrincipal; System.out.printf("%d, %.2f, %.2f, %.2f", paymentNumber++, monthlyInterest, monthlyPrincipalPaid, loanAmount); } } /* //method to print first payment public double getFirstPayment() { } method to print last payment public double getLastPayment() { }*/ private Person client; private int loanId; private double interestRate; private int loanLength; private double loanAmount; private static int nextId = 1; } Thanks!

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  • c++ class member functions instatiated by traits

    - by Jive Dadson
    I am reluctant to say I can't figure this out, but I can't figure this out. I've googled and searched stackoverflow, and come up empty. The abstract, and possibly overly vague form of the question is, how can I use the traits-pattern to instantiate non-virtual member functions? The question came up while modernizing a set of multivariate function optimizers that I wrote more than 10 years ago. The optimizers all operate by selecting a straight-line path through the parameter space away from the current best point (the "update"), then finding a better point on that line (the "line search"), then testing for the "done" condition, and if not done, iterating. There are different methods for doing the update, the line-search, and conceivably for the done test, and other things. Mix and match. Different update formulae require different state-variable data. For example, the LMQN update requires a vector, and the BFGS update requires a matrix. If evaluating gradients is cheap, the line-search should do so. If not, it should use function evaluations only. Some methods require more accurate line-searches than others. Those are just some examples. The original version instantiates several of the combinations by means of virtual functions. Some traits are selected by setting mode bits that are tested at runtime. Yuck. It would be trivial to define the traits with #define's and the member functions with #ifdef's and macros. But that's so twenty years ago. It bugs me that I cannot figure out a whiz-bang modern way. If there were only one trait that varied, I could use the curiously recurring template pattern. But I see no way to extend that to arbitrary combinations of traits. I tried doing it using boost::enable_if, etc.. The specialized state info was easy. I managed to get the functions done, but only by resorting to non-friend external functions that have the this-pointer as a parameter. I never even figured out how to make the functions friends, much less member functions. The compiler (vc++ 2008) always complained that things didn't match. I would yell, "SFINAE, you moron!" but the moron is probably me. Perhaps tag-dispatch is the key. I haven't gotten very deeply into that. Surely it's possible, right? If so, what is best practice?

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  • Any way to allow classes implementing IEntity and downcast to have operator == comparisons?

    - by George Mauer
    Basically here's the issue. All entities in my system are identified by their type and their id. new Customer() { Id = 1} == new Customer() {Id = 1}; new Customer() { Id = 1} != new Customer() {Id = 2}; new Customer() { Id = 1} != new Product() {Id = 1}; Pretty standard scenario. Since all Entities have an Id I define an interface for all entities. public interface IEntity { int Id { get; set;} } And to simplify creation of entities I make public abstract class BaseEntity<T> : where T : IEntity { int Id { get; set;} public static bool operator ==(BaseEntity<T> e1, BaseEntity<T> e2) { if (object.ReferenceEquals(null, e1)) return false; return e1.Equals(e2); } public static bool operator !=(BaseEntity<T> e1, BaseEntity<T> e2) { return !(e1 == e2); } } where Customer and Product are something like public class Customer : BaseEntity<Customer>, IEntity {} public class Product : BaseEntity<Product>, IEntity {} I think this is hunky dory. I think all I have to do is override Equals in each entity (if I'm super clever, I can even override it only once in the BaseEntity) and everything with work. So now I'm expanding my test coverage and find that its not quite so simple! First of all , when downcasting to IEntity and using == the BaseEntity< override is not used. So what's the solution? Is there something else I can do? If not, this is seriously annoying. Upadate It would seem that there is something wrong with my tests - or rather with comparing on generics. Check this out [Test] public void when_created_manually_non_generic() { // PASSES! var e1 = new Terminal() {Id = 1}; var e2 = new Terminal() {Id = 1}; Assert.IsTrue(e1 == e2); } [Test] public void when_created_manually_generic() { // FAILS! GenericCompare(new Terminal() { Id = 1 }, new Terminal() { Id = 1 }); } private void GenericCompare<T>(T e1, T e2) where T : class, IEntity { Assert.IsTrue(e1 == e2); } Whats going on here? This is not as big a problem as I was afraid, but is still quite annoying and a completely unintuitive way for the language to behave. Update Update Ah I get it, the generic implicitly downcasts to IEntity for some reason. I stand by this being unintuitive and potentially problematic for my Domain's consumers as they need to remember that anything happening within a generic method or class needs to be compared with Equals()

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  • Representing xml through a single class

    - by Charles
    I am trying to abstract away the difficulties of configuring an application that we use. This application takes a xml configuration file and it can be a bit bothersome to manually edit this file, especially when we are trying to setup some automatic testing scenarios. I am finding that reading xml is nice, pretty easy, you get a network of element nodes that you can just go through and build your structures quite nicely. However I am slowly finding that the reverse is not quite so nice. I want to be able to build a xml configuration file through a single easy to use interface and because xml is composed of a system of nodes I am having a lot of struggle trying to maintain the 'easy' part. Does anyone know of any examples or samples that easily and intuitively build xml files without declaring a bunch of element type classes and expect the user to build the network themselves? For example if my desired xml output is like so <cook version="1.1"> <recipe name="chocolate chip cookie"> <ingredients> <ingredient name="flour" amount="2" units="cups"/> <ingredient name="eggs" amount="2" units="" /> <ingredient name="cooking chocolate" amount="5" units="cups" /> </ingredients> <directions> <direction name="step 1">Preheat oven</direction> <direction name="step 2">Mix flour, egg, and chocolate</direction> <direction name="step 2">bake</direction> </directions> </recipe> <recipe name="hot dog"> ... How would I go about designing a class to build that network of elements and make one easy to use interface for creating recipes? Right now I have a recipe object, an ingredient object, and a direction object. The user must make each one, set the attributes in the class and attach them to the root object which assembles the xml elements and outputs the formatted xml. Its not very pretty and I just know there has to be a better way. I am using python so bonus points for pythonic solutions

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  • Is it Bad Practice to use C++ only for the STL containers?

    - by gmatt
    First a little background ... In what follows, I use C,C++ and Java for coding (general) algorithms, not gui's and fancy program's with interfaces, but simple command line algorithms and libraries. I started out learning about programming in Java. I got pretty good with Java and I learned to use the Java containers a lot as they tend to reduce complexity of book keeping while guaranteeing great performance. I intermittently used C++, but I was definitely not as good with it as with Java and it felt cumbersome. I did not know C++ enough to work in it without having to look up every single function and so I quickly reverted back to sticking to Java as much as possible. I then made a sudden transition into cracking and hacking in assembly language, because I felt I was concentrated too much attention on a much too high level language and I needed more experience with how a CPU interacts with memory and whats really going on with the 1's and 0's. I have to admit this was one of the most educational and fun experiences I've had with computers to date. For obviously reasons, I could not use assembly language to code on a daily basis, it was mostly reserved for fun diversions. After learning more about the computer through this experience I then realized that C++ is so much closer to the "level of 1's and 0's" than Java was, but I still felt it to be incredibly obtuse, like a swiss army knife with far too many gizmos to do any one task with elegance. I decided to give plain vanilla C a try, and I quickly fell in love. It was a happy medium between simplicity and enough "micromanagent" to not abstract what is really going on. However, I did miss one thing about Java: the containers. In particular, a simple container (like the stl vector) that expands dynamically in size is incredibly useful, but quite a pain to have to implement in C every time. Hence my code currently looks like almost entirely C with containers from C++ thrown in, the only feature I use from C++. I'd like to know if its consider okay in practice to use just one feature of C++, and ignore the rest in favor of C type code?

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  • Is there a reason why a base class decorated with XmlInclude would still throw a type unknown exception when serialized?

    - by Tedford
    I will simplify the code to save space but what is presented does illustrate the core problem. I have a class which has a property that is a base type. There exist 3 dervived classes which could be assigned to that property. If I assign any of the derived classes to the container then the XmlSerializer throws dreaded "The type xxx was not expected. Use the XmlInclude or SoapInclude attribute to specify types that are not known statically." exception when attempting to seralize the container. However my base class is already decorated with that attribute so I figure there must be an additional "hidden" requirement. The really odd part is that the default WCF serializer has no issues with this class hierarchy. The Container class [DataContract] [XmlRoot(ElementName = "TRANSACTION", Namespace = Constants.Namespace)] public class PaymentSummaryRequest : CommandRequest { /// <summary> /// Gets or sets the summary. /// </summary> /// <value>The summary.</value> /// <remarks></remarks> [DataMember] public PaymentSummary Summary { get; set; } /// <summary> /// Initializes a new instance of the <see cref="PaymentSummaryRequest"/> class. /// </summary> public PaymentSummaryRequest() { Mechanism = CommandMechanism.PaymentSummary; } } The base class [DataContract] [XmlInclude(typeof(xxxPaymentSummary))] [XmlInclude(typeof(yyyPaymentSummary))] [XmlInclude(typeof(zzzPaymentSummary))] [KnownType(typeof(xxxPaymentSummary))] [KnownType(typeof(xxxPaymentSummary))] [KnownType(typeof(zzzPaymentSummary))] public abstract class PaymentSummary { } One of the derived classes [DataContract] public class xxxPaymentSummary : PaymentSummary { } The serialization code var serializer = new XmlSerializer(typeof(PaymentSummaryRequest)); serializer.Serialize(Console.Out,new PaymentSummaryRequest{Summary = new xxxPaymentSummary{}}); The Exception System.InvalidOperationException: There was an error generating the XML document. --- System.InvalidOperationException: The type xxxPaymentSummary was not expected. Use the XmlInclude or SoapInclude attribute to specify types that are not known statically. at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationWriterPaymentSummaryRequest.Write13_PaymentSummary(String n, String ns, PaymentSummary o, Boolean isNullable, Boolean needType) at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationWriterPaymentSummaryRequest.Write14_PaymentSummaryRequest(String n, String ns, PaymentSummaryRequest o, Boolean isNullable, Boolean needType) at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationWriterPaymentSummaryRequest.Write15_TRANSACTION(Object o) --- End of inner exception stack trace --- at System.Xml.Serialization.XmlSerializer.Serialize(XmlWriter xmlWriter, Object o, XmlSerializerNamespaces namespaces, String encodingStyle, String id) at System.Xml.Serialization.XmlSerializer.Serialize(TextWriter textWriter, Object o, XmlSerializerNamespaces namespaces) at UserQuery.RunUserAuthoredQuery() in c:\Users\Tedford\AppData\Local\Temp\uqacncyo.0.cs:line 47

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  • Java loading user-specified classes at runtime

    - by user349043
    I'm working on robot simulation in Java (a Swing application). I have an abstract class "Robot" from which different types of Robots are derived, e.g. public class StupidRobot extends Robot { int m_stupidness; int m_insanityLevel; ... } public class AngryRobot extends Robot { float m_aggression; ... } As you can see, each Robot subclass has a different set of parameters. What I would like to do is control the simulation setup in the initial UI. Choose the number and type of Robots, give it a name, fill in the parameters etc. This is one of those times where being such a dinosaur programmer, and new to Java, I wonder if there is some higher level stuff/thinking that could help me here. So here is what I've got: (1) User Interface Scrolling list of Robot types on the left. "Add " and "<< Remove" buttons in the middle. Default-named scrolling list of Robots on the right. "Set Parameters" button underneath. (So if you wanted an AngryRobot, you'd select AngryRobot on the left list, click "Add" and "AngryRobot1" would show up on the right.) When selecting a Robot on the right, click "Set Parameters..." button which would call yet another model dialog where you'd fill in the parameters. Different dialog called for each Robot type. (2) Data structures an implementation As an end-product I think a HashMap would be most convenient. The keys would be Robot types and the accompanying object would be all of the parameters. The initializer could just retrieve each item one and a time and instantiate. Here's what the data structures would look like: enum ROBOT_TYPE {STUPID, ANGRY, etc} public class RobotInitializer { public ROBOT_TYPE m_type; public string m_name; public int[] m_int_params; public float[] m_float_params; etc. The initializer's constructor would create the appropriate length parameter arrays based on the type: public RobotInitializer(ROBOT_TYPE type, int[] int_array, float[] float_array, etc){ switch (type){ case STUPID: m_int_params = new int[STUPID_INT_PARAM_LENGTH]; System.arraycopy(int_array,0,m_int_params,0,STUPID_INT_PARAM_LENGTH); etc. Once all the RobotInitializers are instantiated, they are added to the HashMap. Iterating through the HashMap, the simulation initializer takes items from the Hashmap and instantiates the appropriate Robots. Is this reasonable? If not, how can it be improved? Thanks

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  • MetadataType and client validation in ASP.NET MVC 2

    - by Kristoffer Ahl
    Inherited properties and MetadataType does not seem to work with client side validation in ASP.NET MVC 2. The validation of our MetadataTypes work as expected on the server but for some reason it does not generate the appropriate client scripts for it. Client side validation kicks in as expected for properties with the DataAnnotations attributes set on the PersonView so I know that client side validation is active and that it works. Does anyone know if or how it can be fixed? Here's what we have: public abstract class PersonView { public string FirstName { get; set; } public string LastName { get; set; } public string Email { get; set; } [Required] public string PhoneNumber { get; set; } public string AddressLine1 { get; set; } public string AddressLine2 { get; set; } public string AddressZipCode { get; set; } public string AddressCity { get; set; } public string AddressCountry { get; set; } } [MetadataType(typeof(CustomerViewMetaData))] public class CustomerView : PersonView {} [MetadataType(typeof(GuestViewMetaData))] public class GuestView : PersonView {} public class GuestViewMetaData { [Required(ErrorMessage = "The guests firstname is required")] public string FirstName { get; set; } [Required(ErrorMessage = "The guests lastname is required")] public string LastName { get; set; } } public class CustomerViewMetaData { [Required(ErrorMessage = "The customers firstname is required")] public string FirstName { get; set; } [Required(ErrorMessage = "The customers lastname is required")] public string LastName { get; set; } [Required(ErrorMessage = "The customers emails is required")] public string Email { get; set; } } As you can see, it's nothing fancy or strange in there... Can it be fixed? Is it a bug in ASP.NET MVC 2?

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  • angular-ui-router : breadcrumps ok but view ko

    - by anakin59490
    this is my app.router.js : agentRouter.config([ '$stateProvider', '$urlRouterProvider', function($stateProvider, $urlRouterProvider) { var root = { name: 'root', abstract: true, url: '', title: 'home', views: { 'header': { templateUrl: 'views/headers/header.app.html', controller: 'HeaderCtrl' }, 'body': { templateUrl: "views/root.html" }, 'footer': { templateUrl: 'views/footers/footer.app.html' } } }; var agent = { name: 'root.agent', url: '/agent', title: 'agent', views: { 'root.sidebar': { templateUrl: "views/main.sidebar.html" }, 'root.container': { templateUrl: "views/partials/agent/list.container.html" } } }; var detail = { name: 'root.agent.detail', url: '/detail/:id', title: 'agentDetail', // use for breadcrumb views: { 'root.sidebar': { templateUrl: "views/main.sidebar.html" }, 'root.container': { templateUrl: "views/partials/agent/list.chantier.html" } } }; /.../ $stateProvider.state(root); $stateProvider.state(agent); $stateProvider.state(detail); } ]); and this is my root.html : <!--Breadcrumb content--> <ul class="row breadcrumb"> <i class="glyphicon glyphicon-home" style=""></i> <li ng-repeat="state in $state.$current.path"> <a ng-href="#{{state.url.format($stateParams)}}"><span ng-bind="state.title"></span></a> <span ng-hide="$last" class=""></span> </li> </ul> <!--Sidebar content--> <div ui-view="root.sidebar">default root.sidebar</div> <!--Container content--> <div style="background-color: #f9f9f9" ui-view="root.container">default root.container</div> I can access to my "agent" page (a list of person) and my breadcrumb is right : home / agent but when i click on an item of the list i got always the same page but my breadcrumb is right : home / agent / agentDetail but in app.router.js if change detail like this : var detail = { name: 'root.detail', // référence initiale + detail (fils) url: '/agent/detail/:id', // réference utilisée dans les fichiers HTML, attention c'est la suite de l'url précédente!!! title: 'agentDetail', // référence utilisée pour le breadcump views: { 'root.sidebar': { templateUrl: "views/main.sidebar.html" }, 'root.container': { templateUrl: "views/partials/agent/list.chantier.html" } } }; i got the right page (list.chantier.xml) but the breadcrumb is false : home / agentDetail instead of home / agent / agentDetail I would like to got the right breadcrumb (home / agent / agentDetail) with the right page (list.chantier.html) when i click on an item of the agent list page (list.container.html) Thank you in advance for your help

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  • Robust way to save/load objects with dependencies?

    - by mrteacup
    I'm writing an Android game in Java and I need a robust way to save and load application state quickly. The question seems to apply to most OO languages. To understand what I need to save: I'm using a Strategy pattern to control my game entities. The idea is I have a very general Entity class which e.g. stores the location of a bullet/player/enemy and I then attach a Behaviour class that tells the entity how to act: class Entiy { float x; float y; Behavior b; } abstract class Behavior { void update(Entity e); {} // Move about at a constant speed class MoveBehavior extends Behavior { float speed; void update ... } // Chase after another entity class ChaseBehavior extends Behavior { Entity target; void update ... } // Perform two behaviours in sequence class CombineBehavior extends Behavior { Behaviour a, b; void update ... } Essentially, Entity objects are easy to save but Behaviour objects can have a semi-complex graph of dependencies between other Entity objects and other Behaviour objects. I also have cases where a Behaviour object is shared between entities. I'm willing to change my design to make saving/loading state easier, but the above design works really well for structuring the game. Anyway, the options I've considered are: Use Java serialization. This is meant to be really slow in Android (I'll profile it sometime). I'm worried about robustness when changes are made between versions however. Use something like JSON or XML. I'm not sure how I would cope with storing the dependencies between objects however. Would I have to give each object a unique ID and then use these IDs on loading to link the right objects together? I thought I could e.g. change the ChaseBehaviour to store a ID to an entity, instead of a reference, that would be used to look up the Entity before performing the behaviour. I'd rather avoid having to write lots of loading/saving code myself as I find it really easy to make mistakes (e.g. forgetting to save something, reading things out in the wrong order). Can anyone give me any tips on good formats to save to or class designs that make saving state easier?

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  • Which is the "best" data access framework/approach for C# and .NET?

    - by Frans
    (EDIT: I made it a community wiki as it is more suited to a collaborative format.) There are a plethora of ways to access SQL Server and other databases from .NET. All have their pros and cons and it will never be a simple question of which is "best" - the answer will always be "it depends". However, I am looking for a comparison at a high level of the different approaches and frameworks in the context of different levels of systems. For example, I would imagine that for a quick-and-dirty Web 2.0 application the answer would be very different from an in-house Enterprise-level CRUD application. I am aware that there are numerous questions on Stack Overflow dealing with subsets of this question, but I think it would be useful to try to build a summary comparison. I will endeavour to update the question with corrections and clarifications as we go. So far, this is my understanding at a high level - but I am sure it is wrong... I am primarily focusing on the Microsoft approaches to keep this focused. ADO.NET Entity Framework Database agnostic Good because it allows swapping backends in and out Bad because it can hit performance and database vendors are not too happy about it Seems to be MS's preferred route for the future Complicated to learn (though, see 267357) It is accessed through LINQ to Entities so provides ORM, thus allowing abstraction in your code LINQ to SQL Uncertain future (see Is LINQ to SQL truly dead?) Easy to learn (?) Only works with MS SQL Server See also Pros and cons of LINQ "Standard" ADO.NET No ORM No abstraction so you are back to "roll your own" and play with dynamically generated SQL Direct access, allows potentially better performance This ties in to the age-old debate of whether to focus on objects or relational data, to which the answer of course is "it depends on where the bulk of the work is" and since that is an unanswerable question hopefully we don't have to go in to that too much. IMHO, if your application is primarily manipulating large amounts of data, it does not make sense to abstract it too much into objects in the front-end code, you are better off using stored procedures and dynamic SQL to do as much of the work as possible on the back-end. Whereas, if you primarily have user interaction which causes database interaction at the level of tens or hundreds of rows then ORM makes complete sense. So, I guess my argument for good old-fashioned ADO.NET would be in the case where you manipulate and modify large datasets, in which case you will benefit from the direct access to the backend. Another case, of course, is where you have to access a legacy database that is already guarded by stored procedures. ASP.NET Data Source Controls Are these something altogether different or just a layer over standard ADO.NET? - Would you really use these if you had a DAL or if you implemented LINQ or Entities? NHibernate Seems to be a very powerful and powerful ORM? Open source Some other relevant links; NHibernate or LINQ to SQL Entity Framework vs LINQ to SQL

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