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  • How can I implement CRUD operations in a base class for an entity framework app?

    - by hminaya
    I'm working a simple EF/MVC app and I'm trying to implement some Repositories to handle my entities. I've set up a BaseObject Class and a IBaseRepository Interface to handle the most basic operations so I don't have to repeat myself each time: public abstract class BaseObject<T> { public XA.Model.Entities.XAEntities db; public BaseObject() { db = new Entities.XAEntities(); } public BaseObject(Entities.XAEntities cont) { db = cont; } public void Delete(T entity) { db.DeleteObject(entity); db.SaveChanges(); } public void Update(T entity) { db.AcceptAllChanges(); db.SaveChanges(); } } public interface IBaseRepository<T> { void Add(T entity); T GetById(int id); IQueryable<T> GetAll(); } But then I find myself having to implement 3 basic methods in every Repository ( Add, GetById & GetAll): public class AgencyRepository : Framework.BaseObject<Agency>, Framework.IBaseRepository<Agency> { public void Add(Agency entity) { db.Companies.AddObject(entity); db.SaveChanges(); } public Agency GetById(int id) { return db.Companies.OfType<Agency>().FirstOrDefault(x => x.Id == id); } public IQueryable<Agency> GetAll() { var agn = from a in db.Companies.OfType<Agency>() select a; return agn; } } How can I get these into my BaseObject Class so I won't run in conflict with DRY.

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  • DRYing out implementation of ICloneable in several classes

    - by Sarah Vessels
    I have several different classes that I want to be cloneable: GenericRow, GenericRows, ParticularRow, and ParticularRows. There is the following class hierarchy: GenericRow is the parent of ParticularRow, and GenericRows is the parent of ParticularRows. Each class implements ICloneable because I want to be able to create deep copies of instances of each. I find myself writing the exact same code for Clone() in each class: object ICloneable.Clone() { object clone; using (var stream = new MemoryStream()) { var formatter = new BinaryFormatter(); // Serialize this object formatter.Serialize(stream, this); stream.Position = 0; // Deserialize to another object clone = formatter.Deserialize(stream); } return clone; } I then provide a convenience wrapper method, for example in GenericRows: public GenericRows Clone() { return (GenericRows)((ICloneable)this).Clone(); } I am fine with the convenience wrapper methods looking about the same in each class because it's very little code and it does differ from class to class by return type, cast, etc. However, ICloneable.Clone() is identical in all four classes. Can I abstract this somehow so it is only defined in one place? My concern was that if I made some utility class/object extension method, it would not correctly make a deep copy of the particular instance I want copied. Is this a good idea anyway?

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  • Fluent NHibernate Repository with subclasses

    - by reallyJim
    Having some difficulty understanding the best way to implement subclasses with a generic repository using Fluent NHibernate. I have a base class and two subclasses, say: public abstract class Person { public virtual int PersonId { get; set; } public virtual string FirstName { get; set; } public virtual string LastName { get; set; } } public class Student : Person { public virtual decimal GPA { get; set; } } public class Teacher : Person { public virtual decimal Salary { get; set; } } My Mappings are as follows: public class PersonMap : ClassMap { public PersonMap() { Table("Persons"); Id(x => x.PersonId).GeneratedBy.Identity(); Map(x => x.FirstName); Map(x => x.LastName); } } public class StudentMap : SubclassMap<Student> { public StudentMap() { Table("Students"); KeyColumn("PersonId"); Map(x => x.GPA); } } public class TeacherMap : SubclassMap<Teacher> { public TeacherMap() { Table("Teachers"); KeyColumn("PersonId"); Map(x => x.Salary); } } I use a generic repository to save/retreive/update the entities, and it works great--provided I'm working with Repository--where I already know that I'm working with students or working with teachers. The problem I run into is this: What happens when I have an ID, and need to determine the TYPE of person? If a user comes to my site as PersonId = 23, how do I go about figuring out which type of person it is?

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  • How to Inserting message into View that depends on session value. ASP.NET MVC. Best practice

    - by Andrew Florko
    User have to populate multistep questionnaire web-forms and step messages depend on the option chosen by user at the very beginning. Messages are stored in web.config file. I use asp.net mvc project, strong typed views and keep business logic separated from controller in static class. I don't want to make business logic dependency on web.config. Well, I have to insert message into view that depends on session value. There are at least 2 options how to implement this: View model has property that is populated in controller/businessLogic and rendered in view like <%: Model.HelpMessage1 %>. I have to pass web.config values from controller to businessLogic that makes business logic methods signature too complex. I don't want to make configuration source abstract (in order to let business logic read configuration values from its methods directly) also. Create static helper class that is called from view like <%: ViewHelper.HelpMessage1(Model.Option1) %>. But in this case logic what to show seems to be separated into two classes: business logic & viewHelper. What will you suggest? Thank you in advance!

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  • What OOP pattern to use when only adding new methods, not data?

    - by Jonathon Reinhart
    Hello eveyone... In my app, I have deal with several different "parameters", which derive from IParameter interface, and also ParamBase abstract base class. I currently have two different parameter types, call them FooParameter and BarParameter, which both derive from ParamBase. Obviously, I can treat them both as IParameters when I need to deal with them generically, or detect their specific type when I need to handle their specific functionality. My question lies in specific FooParameters. I currently have a few specific ones with their own classes which derive from FooParameter, we'll call them FP12, FP13, FP14, etc. These all have certain characteristics, which make me treat them differently in the UI. (Most have names associated with the individual bits, or ranges of bits). Note that these specific, derived FP's have no additional data associated with them, only properties (which refer to the same data in different ways) or methods. Now, I'd like to keep all of these parameters in a Dictionary<String, IParameter> for easy generic access. The problem is, if I want to refer to a specific one with the special GUI functions, I can't write: FP12 fp12 = (FP12)paramList["FP12"] because you can't downcast to a derived type (rightfully so). But in my case, I didn't add any data, so the cast would theoretically work. What type of programming model should I be using instead? Thanks!

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  • How do I integrate GUI elements from different classes at runtime?

    - by thefourthdoctor
    I'm trying to "future-proof" an application that I'm writing by splitting out those elements that are likely to change over time. In my application I need to be able to adapt to changes in the output format (e.g. today I output to a CSV file, in the future I may need to output directly to a SQL Server database, or to a web service, etc.). I'm handling this by defining an abstract class ("OutputProvider") that I will subclass for each individual case. The one aspect of this that has me stumped is how to provide a configuration GUI that is specific to each concrete class. I have a settings dialog with a tab for output configuration. On that tab I intend to provide a drop-down to select the provider and a JPanel beneath it to hold the contents of the provider-specific GUI. How do I get the right GUI in that panel at runtime and have it behave correctly with respect to events? Also, a bonus would be if there was a way to do this such that in order to add support for new providers I could simply provide a new jar or class file to be dropped in a specific folder and the application could pick that up at startup. I'm using NetBeans and Swing.

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  • JPA 2.0 Provider Hibernate

    - by Rooh
    I have very strange problem we are using jpa 2.0 with hibernate annotations based Database generated through JPA DDL is true and MySQL as Database; i will provide some reference classes and then my porblem. @MappedSuperclass public abstract class Common implements serializable{ @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "id", updatable = false) private Long id; @ManyToOne @JoinColumn private Address address; //with all getter and setters //as well equal and hashCode } @Entity public class Parent extends Common{ private String name; @OneToMany(cascade = {CascadeType.MERGE,CascadeType.PERSIST}, mappedBy = "parent") private List<Child> child; //setters and rest of class } @Entity public class Child extends Common{ //some properties with getter/setters } @Entity public class Address implements Serializable{ @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "id", updatable = false) private Long id; private String street; //rest of class with get/setter } as in code you can see that parents and child classes extends Common class so both have address property and id , the problem occurs when change the address refference in parent class it reflect same change in all child objects in list and if change address refference in child class then on merge it will change address refference of parent as well i am not able to figure out is it is problem of jpa or hibernate

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  • Building a control-flow graph from an AST with a visitor pattern using Java

    - by omegatai
    Hi guys, I'm trying to figure out how to implement my LEParserCfgVisitor class as to build a control-flow graph from an Abstract-Syntax-Tree already generated with JavaCC. I know there are tools that already exist, but I'm trying to do it in preparation for my Compilers final. I know I need to have a data structure that keeps the graph in memory, and I want to be able to keep attributes like IN, OUT, GEN, KILL in each node as to be able to do a control-flow analysis later on. My main problem is that I haven't figured out how to connect the different blocks together, as to have the right edge between each blocks depending on their nature: branch, loops, etc. In other words, I haven't found an explicit algorithm that could help me build my visitor. Here is my empty Visitor. You can see it works on basic langage expressions, like if, while and basic operations (+,-,x,^,...) public class LEParserCfgVisitor implements LEParserVisitor { public Object visit(SimpleNode node, Object data) { return data; } public Object visit(ASTProgram node, Object data) { data = node.childrenAccept(this, data); return data; } public Object visit(ASTBlock node, Object data) { } public Object visit(ASTStmt node, Object data) { } public Object visit(ASTAssignStmt node, Object data) { } public Object visit(ASTIOStmt node, Object data) { } public Object visit(ASTIfStmt node, Object data) { } public Object visit(ASTWhileStmt node, Object data) { } public Object visit(ASTExpr node, Object data) { } public Object visit(ASTAddExpr node, Object data) { } public Object visit(ASTFactExpr node, Object data) { } public Object visit(ASTMultExpr node, Object data) { } public Object visit(ASTPowerExpr node, Object data) { } public Object visit(ASTUnaryExpr node, Object data) { } public Object visit(ASTBasicExpr node, Object data) { } public Object visit(ASTFctExpr node, Object data) { } public Object visit(ASTRealValue node, Object data) { } public Object visit(ASTIntValue node, Object data) { } public Object visit(ASTIdentifier node, Object data) { } } Can anyone give me a hand? Thanks!

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  • How to specialize a type parameterized argument to multiple different types for in Scala?

    - by jmount
    I need a back-check (please). In an article ( http://www.win-vector.com/blog/2010/06/automatic-differentiation-with-scala/ ) I just wrote I stated that it is my belief in Scala that you can not specify a function that takes an argument that is itself a function with an unbound type parameter. What I mean is you can write: def g(f:Array[Double]=>Double,Array[Double]):Double but you can not write something like: def g(f[Y]:Array[Y]=>Double,Array[Double]):Double because Y is not known. The intended use is that inside g() I will specialize fY to multiple different types at different times. You can write: def g[Y](f:Array[Y]=>Double,Array[Double]):Double but then f() is of a single type per call to g() (which is exactly what we do not want). However, you can get all of the equivalent functionality by using a trait extension instead insisting on passing around a function. What I advocated in my article was: 1) Creating a trait that imitates the structure of Scala's Function1 trait. Something like: abstract trait VectorFN { def apply[Y](x:Array[Y]):Y } 2) declaring def g(f:VectorFN,Double):Double (using the trait is the type). This works (people here on StackOverflow helped me find it, and I am happy with it)- but am I mis-representing Scala by missing an even better solution?

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  • How to model has_many with polymorphism?

    - by Daniel Abrahamsson
    I've run into a situation that I am not quite sure how to model. Suppose I have a User class, and a user has many services. However, these services are quite different, for example a MailService and a BackupService, so single table inheritance won't do. Instead, I am thinking of using polymorphic associations together with an abstract base class: class User < ActiveRecord::Base has_many :services end class Service < ActiveRecord::Base validates_presence_of :user_id, :implementation_id, :implementation_type belongs_to :user belongs_to :implementation, :polymorphic = true delegate :common_service_method, :name, :to => :implementation end #Base class for service implementations class ServiceImplementation < ActiveRecord::Base validates_presence_of :user_id, :on => :create has_one :service, :as => :implementation has_one :user, :through => :service after_create :create_service_record #Tell Rails this class does not use a table. def self.abstract_class? true end #Default name implementation. def name self.class.name end protected #Sets up a service object def create_service_record service = Service.new(:user_id => user_id) service.implementation = self service.save! end end class MailService < ServiceImplementation #validations, etc... def common_service_method puts "MailService implementation of common service method" end end #Example usage MailService.create(..., :user_id => user.id) BackupService.create(...., :user_id => user.id) user.services.each do |s| puts "#{user.name} is using #{s.name}" end #Daniel is using MailService, Daniel is using BackupService So, is this the best solution? Or even a good one? How have you solved this kind of problem?

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  • EF Many-to-many dbset.Include in DAL on GenericRepository

    - by Bryant
    I can't get the QueryObjectGraph to add INCLUDE child tables if my life depended on it...what am I missing? Stuck for third day on something that should be simple :-/ DAL: public abstract class RepositoryBase<T> where T : class { private MyLPL2Context dataContext; private readonly IDbSet<T> dbset; protected RepositoryBase(IDatabaseFactory databaseFactory) { DatabaseFactory = databaseFactory; dbset = DataContext.Set<T>(); DataContext.Configuration.LazyLoadingEnabled = true; } protected IDatabaseFactory DatabaseFactory { get; private set; } protected MyLPL2Context DataContext { get { return dataContext ?? (dataContext = DatabaseFactory.Get()); } } public IQueryable<T> QueryObjectGraph(Expression<Func<T, bool>> filter, params string[] children) { foreach (var child in children) { dbset.Include(child); } return dbset.Where(filter); } ... DAL repositories public interface IBreed_TranslatedSqlRepository : ISqlRepository<Breed_Translated> { } public class Breed_TranslatedSqlRepository : RepositoryBase<Breed_Translated>, IBreed_TranslatedSqlRepository { public Breed_TranslatedSqlRepository(IDatabaseFactory databaseFactory) : base(databaseFactory) {} } BLL Repo: public IQueryable<Breed_Translated> QueryObjectGraph(Expression<Func<Breed_Translated, bool>> filter, params string[] children) { return _r.QueryObjectGraph(filter, children); } Controller: var breeds1 = _breedTranslatedRepository .QueryObjectGraph(b => b.Culture == culture, new string[] { "AnimalType_Breed" }) .ToList(); I can't get to Breed.AnimalType_Breed.AnimalTypeId ..I can drill as far as Breed.AnimalType_Breed then the intelisense expects an expression? Cues if any, DB Tables: bold is many-to-many Breed, Breed_Translated, AnimalType_Breed, AnimalType, ...

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  • adding an uncertain number of fields using javascript

    - by user306472
    I'm new to javascript and a novice programmer, so this might be a really easy question to answer. I would like to loop over the values of x number of fields and add them up to display the sum in a final field. I can perform this function if I explicitly call each field, but I want to abstract this so I can deal with a flexible number of fields. Here's example code I've come up with (that's not working for me). Where am I going wrong? <html> <head> <script type="text/javascript"> function startAdd(){ interval = setInterval("addfields()",1); } function addfields(){ a = document.addition.total.value; b = getElementByTagName("sum").value; for (i=0; i<=b.length; i++){ a+=i; } return a; } function stopAdd(){ clearInterval(interval); } </script> </head> <body> <form name="addition"> <input type="text" name="sum" onFocus="startAdd();" onBlur="stopAdd;"> + <input type="text" name="sum" onFocus="startAdd();" onBlur="stopAdd;"> = <input type="text" name ="total"> </form> </body> </html>

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  • Strongly Typed DataSet column requires custom type to implement IXmlSerializable?

    - by Phil
    I have a strongly typed Dataset with a single table with three columns. These columns all contain custom types. DataColumn1 is of type Parent DataColumn2 is of type Child1 DataColumn3 is of type Child2 Here is what these classes look like: [Serializable] [XmlInclude(typeof(Child1)), XmlInclude(typeof(Child2))] public abstract class Parent { public int p1; } [Serializable] public class Child1 :Parent { public int c1; } [Serializable] public class Child2 : Parent { public int c1; } now, if I add a row with DataColumn1 being null, and DataColumns 2 and 3 populated and try to serialize it, it works: DataSet1 ds = new DataSet1(); ds.DataTable1.AddDataTable1Row(null, new Child1(), new Child2()); StringBuilder sb = new StringBuilder(); using (StringWriter writer = new StringWriter(sb)) { ds.WriteXml(writer);//Works! } However, if I try to add a value to DataColumn1, it fails: DataSet1 ds = new DataSet1(); ds.DataTable1.AddDataTable1Row(new Child1(), new Child1(), new Child2()); StringBuilder sb = new StringBuilder(); using (StringWriter writer = new StringWriter(sb)) { ds.WriteXml(writer);//Fails! } Here is the Exception: "Type 'WindowsFormsApplication4.Child1, WindowsFormsApplication4, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' does not implement IXmlSerializable interface therefore can not proceed with serialization." I have also tried using the XmlSerializer to serialize the dataset, but I get the same exception. Does anyone know of a way to get around this where I don't have to implement IXmlSerializable on all the Child classes? Alternatively, is there a way to implement IXmlSerializable keeping all default behavior the same (ie not having any class specific code in the ReadXml and WriteXml methods)

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  • linear combinations in python/numpy

    - by nmaxwell
    greetings, I'm not sure if this is a dumb question or not. Lets say I have 3 numpy arrays, A1,A2,A3, and 3 floats, c1,c2,c3 and I'd like to evaluate B = A1*c1+ A2*c2+ A3*c3 will numpy compute this as for example, E1 = A1*c1 E2 = A2*c2 E3 = A3*c3 D1 = E1+E2 B = D1+E3 or is it more clever than that? In c++ I had a neat way to abstract this kind of operation. I defined series of general 'LC' template functions, LC for linear combination like: template<class T,class D> void LC( T & R, T & L0,D C0, T & L1,D C1, T & L2,D C2) { R = L0*C0 +L1*C1 +L2*C2; } and then specialized this for various types, so for instance, for an array the code looked like for (int i=0; i<L0.length; i++) R.array[i] = L0.array[i]*C0 + L1.array[i]*C1 + L2.array[i]*C2; thus avoiding having to create new intermediate arrays. This may look messy but it worked really well. I could do something similar in python, but I'm not sure if its nescesary. Thanks in advance for any insight. -nick

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  • using STI and ActiveRecordBase<> with full FindAll

    - by oillio
    Is it possible to use generic support with single table inheritance, and still be able to FindAll of the base class? As a bonus question, will I be able to use ActiveRecordLinqBase< as well? I do love those queries. More detail: Say I have the following classes defined: public interface ICompany { int ID { get; set; } string Name { get; set; } } [ActiveRecord("companies", DiscriminatorColumn="type", DiscriminatorType="String", DiscriminatorValue="NA")] public abstract class Company<T> : ActiveRecordBase<T>, ICompany { [PrimaryKey] private int Id { get; set; } [Property] public String Name { get; set; } } [ActiveRecord(DiscriminatorValue="firm")] public class Firm : Company<Firm> { [Property] public string Description { get; set; } } [ActiveRecord(DiscriminatorValue="client")] public class Client : Company<Client> { [Property] public int ChargeRate { get; set; } } This works fine for most cases. I can do things like: var x = Client.FindAll(); But sometimes I want all of the companies. If I was not using generics I could do: var x = (Company[]) FindAll(Company); Client a = (Client)x[0]; Firm b = (Firm)x[1]; Is there a way to write a FindAll that returns an array of ICompany's that can then be typecast into their respective types? Something like: var x = (ICompany[]) FindAll(Company<ICompany>); Client a = (Client)x[0]; Or maybe I am going about implementing the generic support all wrong?

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  • NHibernate unintential 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_ 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 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 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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  • Javascript CS-PRNG - 64-bit random

    - by Jack
    Hi, I need to generate a cryptographically secure 64-bit unsigned random integer in Javascript. The first problem is that Javascript only allows 64-bit signed integers, so 9223372036854775808 is the biggest supported integer without going into floating point use I think? To fix this I can use a big number library, no problem. My Method: var randNum = SHA256( randBigInt(128, 0) ) % 2^64; Where SHA256() is a secure hash function and randBigInt() is defined below as a non-crypto PRNG, im giving it a 128bit seed so brute force shouldn't be a problem. randBigInt(n,s) //return an n-bit random BigInt (n>=1). If s=1, then the most significant of those n bits is set to 1. Is this a secure method to generate a cryptographically secure 64-bit random int? And importantly does taking the 2^64 mod guarantee 100% I have a 64-bit number? An abstract example, say this number is prime (it isn't i know), I will use it in the Galois Field [2^p], where p must be 64bits so that every possible 1-63bit number is a field element. In this query, my random int must be larger than any 63-bit number. And Im not sure im correct in taking the 2^64 mod of a 256bit hash output. Thanks (hope that makes sense)

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  • Applying the Decorator Pattern to Forms

    - by devoured elysium
    I am trying to apply the Decorator Design Pattern to the following situation: I have 3 different kind of forms: Green, Yellow, Red. Now, each of those forms can have different set of attributes. They can have a minimize box disabled, a maximized box disabled and they can be always on top. I tried to model this the following way: Form <---------------------------------------FormDecorator /\ /\ |---------|-----------| |----------------------|-----------------| GreenForm YellowForm RedForm MinimizeButtonDisabled MaximizedButtonDisabled AlwaysOnTop Here is my GreenForm code: public class GreenForm : Form { public GreenForm() { this.BackColor = Color.GreenYellow; } public override sealed Color BackColor { get { return base.BackColor; } set { base.BackColor = value; } } } FormDecorator: public abstract class FormDecorator : Form { private Form _decoratorForm; protected FormDecorator(Form decoratorForm) { this._decoratorForm = decoratorForm; } } and finally NoMaximizeDecorator: public class NoMaximizeDecorator : FormDecorator { public NoMaximizeDecorator(Form decoratorForm) : base(decoratorForm) { this.MaximizeBox = false; } } So here is the running code: static void Main() { Application.EnableVisualStyles(); Application.SetCompatibleTextRenderingDefault(false); Application.Run(CreateForm()); } static Form CreateForm() { Form form = new GreenForm(); form = new NoMaximizeDecorator(form); form = new NoMinimizeDecorator(form); return form; } The problem is that I get a form that isn't green and that still allows me to maximize it. It is only taking in consideration the NoMinimizeDecorator form. I do comprehend why this happens but I'm having trouble understanding how to make this work with this Pattern. I know probably there are better ways of achieving what I want. I made this example as an attempt to apply the Decorator Pattern to something. Maybe this wasn't the best pattern I could have used(if one, at all) to this kind of scenario. Is there any other pattern more suitable than the Decorator to accomplish this? Am I doing something wrong when trying to implement the Decorator Pattern? Thanks

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  • Most "thorough" distribution of points around a circle

    - by hippietrail
    This question is intended to both abstract and focus one approach to my problem expressed at "Find the most colourful image in a collection of images". Imagine we have a set of circles, each has a number of points around its circumference. We want to find a metric that gives a higher rating to a circle with points distributed evenly around the circle. Circles with some points scattered through the full 360° are better but circles with far greater numbers of points in one area compared to a smaller number in another area are less good. The number of points is not limited. Two or more points may coincide. Coincidental points are still relevant. A circle with one point at 0° and one point at 180° is better than a circle with 100 points at 0° and 1000 points at 180°. A circle with one point every degree around the circle is very good. A circle with a point every half degree around the circle is better. In my other (colour based question) it was suggested that standard deviation would be useful but with caveat. Is this a good suggestion and does it cope with the closeness of 359° to 1°?

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  • dll's loaded through reflection

    - by Seattle Leonard
    Ok, I got a strange one here and I want to know if any of you have ever run accross anything like it. So I've got this web app that loads up a bunch of dll's through reflection. Basically it looks for Types that are derived from certain abstract types and adds them to the list of things it can make. Here's the weird part. While developing there is never a problem. When installing it, there is never a problem to start with. Then, at a seemingly random time, the application breaks while trying to find all the types. I've had 2 sites sitting side by side and one worked while the other did not, and they were configured exactly(and I mean exactly) the same. IISRESET's never helped, but this did: I simply moved all the dll's out of the bin directory then moved them back. That's right I just moved them out of the bin directory then put them right back where they came from and everything worked fine. Any ideas?

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  • iPhone: Calling dealloc on parentViewController causes an exception

    - by arielcamus
    Hi, I'm dealing with viewDidUnload and dealloc methods and I've founded a problem when calling [super dealloc]; in parent view controller. I have a lot of view controllers with custom code which I have putted outside on a parent view controller. So, when defining my view controllers I set a reference to the super class: @interface LoginViewController : AbstractViewController Then, at the dealloc method I call the AbstractViewController dealloc method: //(Login View Controller code) - (void)dealloc { [user release]; [passwd release]; [super dealloc]; } [super dealloc] execute the following code: //(Abstract View Controller code) - (void)dealloc { [dbUtils release]; [loadingView release]; [super dealloc]; } If I simulate a memory warning on iPhone Simulator, the following exception is thrown: 2010-03-03 11:27:45.805 MyApp[71563:40b] Received simulated memory warning. 2010-03-03 11:27:45.808 MyApp[71563:40b] *** -[LoginViewController isViewLoaded]: message sent to deallocated instance 0x13b51b0 kill quit However, if I comment the [super dealloc] line in AbstractViewController the exception is not thrown and my app still running. Thank you for your help once again!

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  • Serializing Configurations for a Dependency Injection / Inversion of Control

    - by Joshua Starner
    I've been researching Dependency Injection and Inversion of Control practices lately in an effort to improve the architecture of our application framework and I can't seem to find a good answer to this question. It's very likely that I have my terminology confused, mixed up, or that I'm just naive to the concept right now, so any links or clarification would be appreciated. Many examples of DI and IoC containers don't illustrate how the container will connect things together when you have a "library" of possible "plugins", or how to "serialize" a given configuration. (From what I've read about MEF, having multiple declarations of [Export] for the same type will not work if your object only requires 1 [Import]). Maybe that's a different pattern or I'm blinded by my current way of thinking. Here's some code for an example reference: public abstract class Engine { } public class FastEngine : Engine { } public class MediumEngine : Engine { } public class SlowEngine : Engine { } public class Car { public Car(Engine e) { engine = e; } private Engine engine; } This post talks about "Fine-grained context" where 2 instances of the same object need different implementations of the "Engine" class: http://stackoverflow.com/questions/2176833/ioc-resolve-vs-constructor-injection Is there a good framework that helps you configure or serialize a configuration to achieve something like this without hard coding it or hand-rolling the code to do this? public class Application { public void Go() { Car c1 = new Car(new FastEngine()); Car c2 = new Car(new SlowEngine()); } } Sample XML: <XML> <Cars> <Car name="c1" engine="FastEngine" /> <Car name="c2" engine="SlowEngine" /> </Cars> </XML>

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  • How to encapsulate a third party complex object structure?

    - by tangens
    Motivation Currently I'm using the java parser japa to create an abstract syntax tree (AST) of a java file. With this AST I'm doing some code generation (e.g.: if there's an annotation on a method, create some other source files, ...) Problem When my code generation becomes more complex, I've to dive deeper into the structure of the AST (e.g. I have to use visitors to extract some type information of method parameters). But I'm not sure if I want to stay with japa or if I will change the parser library later. Because my code generator uses freemarker (which isn't good at automatic refactoring) I want the interface that it uses to access the AST information to be stable, even if I decide to change the java parser. Question What's the best way to encapsulate complex datastructures of third party libraries? I could create my own datatypes and copy the parts of the AST that I need into these. I could create lots of specialized access methods that work with the AST and create exactly the infos I need (e.g. the fully qualified return type of a method as one string, or the first template parameter of a class). I could create wrapper classes for the japa datastructures I currently need and embed the japa types inside, so that I can delegate requests to the japa types and transform the resulting japa types to my wrapper classes again. Which solution should I take? Are there other (better) solutions to this problem?

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  • What is wrong with locking non-static fields? What is the correct way to lock a particular instance?

    - by smartcaveman
    Why is it considered bad practice to lock non-static fields? And, if I am not locking non-static fields, then how do I lock an instance method without locking the method on all other instances of the same or derived class? I wrote an example to make my question more clear. public abstract class BaseClass { private readonly object NonStaticLockObject = new object(); private static readonly object StaticLockObject = new object(); protected void DoThreadSafeAction<T>(Action<T> action) where T: BaseClass { var derived = this as T; if(derived == null) { throw new Exception(); } lock(NonStaticLockObject) { action(derived); } } } public class DerivedClass :BaseClass { private readonly Queue<object> _queue; public void Enqueue(object obj) { DoThreadSafeAction<DerivedClass>(x=>x._queue.Enqueue(obj)); } } If I make the lock on the StaticLockObject, then the DoThreadSafeAction method will be locked for all instances of all classes that derive from BaseClass and that is not what I want. I want to make sure that no other threads can call a method on a particular instance of an object while it is locked.

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  • Auto increment with a Unit Of Work

    - by Derick
    Context I'm building a persistence layer to abstract different types of databases that I'll be needing. On the relational part I have mySQL, Oracle and PostgreSQL. Let's take the following simplified MySQL tables: CREATE TABLE Contact ( ID varchar(15), NAME varchar(30) ); CREATE TABLE Address ( ID varchar(15), CONTACT_ID varchar(15), NAME varchar(50) ); I use code to generate system specific alpha numeric unique ID's fitting 15 chars in this case. Thus, if I insert a Contact record with it's Addresses I have my generated Contact.ID and Address.CONTACT_IDs before committing. I've created a Unit of Work (amongst others) as per Martin Fowler's patterns to add transaction support. I'm using a key based Identity Map in the UoW to track the changed records in memory. It works like a charm for the scenario above, all pretty standard stuff so far. The question scenario comes in when I have a database that is not under my control and the ID fields are auto-increment (or in Oracle sequences). In this case I do not have the db generated Contact.ID beforehand, so when I create my Address I do not have a value for Address.CONTACT_ID. The transaction has not been started on the DB session since all is kept in the Identity Map in memory. Question: What is a good approach to address this? (Avoiding unnecessary db round trips) Some ideas: Retrieve the last ID: I can do a call to the database to retrieve the last Id like: SELECT Auto_increment FROM information_schema.tables WHERE table_name='Contact'; But this is MySQL specific and probably something similar can be done for the other databases. If do this then would need to do the 1st insert, get the ID and then update the children (Address.CONTACT_IDs) – all in the current transaction context.

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