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• The problems with Avoiding Smurf Naming classes with namespaces

  - by Daniel Koverman

  I pulled the term smurf naming from here (number 21). To save anyone not familiar the trouble, Smurf naming is the act of prefixing a bunch of related classes, variables, etc with a common prefix so you end up with "a SmurfAccountView passes a SmurfAccountDTO to the SmurfAccountController", etc. The solution I've generally heard to this is to make a smurf namespace and drop the smurf prefixes. This has generally served me well, but I'm running into two problems. I'm working with a library with a Configuration class. It could have been called WartmongerConfiguration but it's in the Wartmonger namespace, so it's just called Configuration. I likewise have a Configuration class which could be called SmurfConfiguration, but it is in the Smurf namespace so that would be redundant. There are places in my code where Smurf.Configuration appears alongside Wartmonger.Configuration and typing out fully qualified names is clunky and makes the code less readable. It would be nicer to deal with a SmurfConfiguration and (if it was my code and not a library) WartmongerConfiguration. I have a class called Service in my Smurf namespace which could have been called SmurfService. Service is a facade on top of a complex Smurf library which runs Smurf jobs. SmurfService seems like a better name because Service without the Smurf prefix is so incredibly generic. I can accept that SmurfService was already a generic, useless name and taking away smurf merely made this more apparent. But it could have been named Runner, Launcher, etc and it would still "feel better" to me as SmurfLauncher because I don't know what a Launcher does, but I know what a SmurfLauncher does. You could argue that what a Smurf.Launcher does should be just as apparent as a Smurf.SmurfLauncher, but I could see `Smurf.Launcher being some kind of class related to setup rather than a class that launches smurfs. If there is an open and shut way to deal with either of these that would be great. If not, what are some common practices to mitigate their annoyance?

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• Moving my sprite in XNA using classes

  - by Tom

  Hey, im a newbie at this programming lark and its really frustrating me. I'm trying to move a snake in all directions while using classes. Ive created a vector2 for speed and ive attempted creating a method which moves the snake within the snake class. Now I'm confused and not sure what to do next. Appreciate any help. Thanks :D This is what i've done in terms of the method... public Vector2 direction() { Vector2 inputDirection = Vector2.Zero; if (Keyboard.GetState().IsKeyDown(Keys.Left)) inputDirection.X -= -1; if (Keyboard.GetState().IsKeyDown(Keys.Right)) inputDirection.X += 1; if (Keyboard.GetState().IsKeyDown(Keys.Up)) inputDirection.Y -= -1; if (Keyboard.GetState().IsKeyDown(Keys.Down)) inputDirection.Y += 1; return inputDirection * snakeSpeed; } Appreciate any help. Thanks :D EDIT: Well let me make everything clear. Im making a small basic game for an assignment. The game is similar to the old snake game on the old Nokia phones. I've created a snake class (even though I'm not sure whether this is needed because im only going to be having one moving sprite within the game). After I written the code above (in the snake class), the game ran with no errors but I couldn't actually move the image :( EDIT2: Thanks so much for everyones responses!!

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• Data classes: getters and setters or different method design

  - by Frog

  I've been trying to design an interface for a data class I'm writing. This class stores styles for characters, for example whether the character is bold, italic or underlined. But also the font-size and the font-family. So it has different types of member variables. The easiest way to implement this would be to add getters and setters for every member variable, but this just feels wrong to me. It feels way more logical (and more OOP) to call style.format(BOLD, true) instead of style.setBold(true). So to use logical methods insteads of getters/setters. But I am facing two problems while implementing these methods: I would need a big switch statement with all member variables, since you can't access a variable by the contents of a string in C++. Moreover, you can't overload by return type, which means you can't write one getter like style.getFormatting(BOLD) (I know there are some tricks to do this, but these don't allow for parameters, which I would obviously need). However, if I would implement getters and setters, there are also issues. I would have to duplicate quite some code because styles can also have a parent styles, which means the getters have to look not only at the member variables of this style, but also at the variables of the parent styles. Because I wasn't able to figure out how to do this, I decided to ask a question a couple of weeks ago. See Object Oriented Programming: getters/setters or logical names. But in that question I didn't stress it would be just a data object and that I'm not making a text rendering engine, which was the reason one of the people that answered suggested I ask another question while making that clear (because his solution, the decorator pattern, isn't suitable for my problem). So please note that I'm not creating my own text rendering engine, I just use these classes to store data. Because I still haven't been able to find a solution to this problem I'd like to ask this question again: how would you design a styles class like this? And why would you do that? Thanks on forehand!

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• Extract all related class type aliasing and enum into one file or not

  - by Chen OT

  I have many models in my project, and some other classes just need the class declaration and pointer type aliasing. It does not need to know the class definition, so I don't want to include the model header file. I extract all the model's declaration into one file to let every classes reference one file. model_forward.h class Cat; typedef std::shared_ptr<Cat> CatPointerType; typedef std::shared_ptr<const Cat> CatConstPointerType; class Dog; typedef std::shared_ptr<Dog> DogPointerType; typedef std::shared_ptr<const Dog> DogConstPointerType; class Fish; typedef std::shared_ptr<Fish> FishPointerType; typedef std::shared_ptr<const Fish> FishConstPointerType; enum CatType{RED_CAT, YELLOW_CAT, GREEN_CAT, PURPLE_CAT} enum DogType{HATE_CAT_DOG, HUSKY, GOLDEN_RETRIEVER} enum FishType{SHARK, OCTOPUS, SALMON} Is it acceptable practice? Should I make every unit, which needs a class declaration, depends on one file? Does it cause high coupling? Or I should put these pointer type aliasing and enum definition inside the class back? cat.h class Cat { typedef std::shared_ptr<Cat> PointerType; typedef std::shared_ptr<const Cat> ConstPointerType; enum Type{RED_CAT, YELLOW_CAT, GREEN_CAT, PURPLE_CAT} ... }; dog.h class Dog { typedef std::shared_ptr<Dog> PointerType; typedef std::shared_ptr<const Dog> ConstPointerType; enum Type{HATE_CAT_DOG, HUSKY, GOLDEN_RETRIEVER} ... } fish.h class Fish { ... }; Any suggestion will be helpful.

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• Breaking up classes and methods into smaller units

  - by micahhoover

  During code reviews a couple devs have recommended I break up my methods into smaller methods. Their justification was (1) increased readability and (2) the back trace that comes back from production showing the method name is more specific to the line of code that failed. There may have also been some colorful words about functional programming. Additionally I think I may have failed an interview a while back because I didn't give an acceptable answer about when to break things up. My inclination is that when I see a bunch of methods in a class or across a bunch of files, it isn't clear to me how they flow together, and how many times each one gets called. I don't really have a good feel for the linearity of it as quickly just by eye-balling it. The other thing is a lot of people seem to place a premium of organization over content (e.g. 'Look at how organized my sock drawer is!' Me: 'Overall, I think I can get to my socks faster if you count the time it took to organize them'). Our business requirements are not very stable. I'm afraid that if the classes/methods are very granular it will take longer to refactor to requirement changes. I'm not sure how much of a factor this should be. Anyway, computer science is part art / part science, but I'm not sure how much this applies to this issue.

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• 7 drived classes with one common base class

  - by user144905

  i have written the following code, //main.cpp #include<iostream> #include<string> #include"human.h" #include"computer.h" #include"referee.h" #include"RandomComputer.h" #include"Avalanche.h" #include"Bureaucrat.h" #include"Toolbox.h" #include"Crescendo.h" #include"PaperDoll.h" #include"FistfullODollors.h" using namespace std; int main() { Avalanche pla1; Avalanche pla2; referee f; pla1.disp(); for (int i=0;i<5;i++) { cout<<pla2.mov[i]; } return 0; } in this program all included classes except referee.h and human.h are drived from computer.h. each drived calls has a char array variable which is initialized when a member of a drived class is declared. the problem is that when i declare tow diffrent drived class memebers lets say Avalache and ToolBox. upon printing the char array for one of them using for loop it prints nothing. However if i declare only one of them in main.cpp the it works properly. and the file for computer.h is as such: #ifndef COMPUTER_H #define COMPUTER_H class computer { public: int nump; char mov[]; void disp(); }; #endif ToolBox.h is like this: #ifndef TOOLBOX_H #define TOOLBOX_H #include"computer.h" class Toolbox: public computer { public: Toolbox(); }; #endif finally Avalanche.h is as following: #ifndef AVALANCHE_H #define AVALANCHE_H #include"computer.h" class Avalanche: public computer { public: Avalanche(); }; #endif

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• How to model an address type in DDD?

  - by Songo

  I have an User entity that has a Set of Address where Address is a value object: class User{ ... private Set<Address> addresses; ... public setAddresses(Set<Address> addresses){ //set all addresses as a batch } ... } A User can have a home address and a work address, so I should have something that acts as a look up in the database: tbl_address_type ------------------------------------------------ | address_type_id | address_type | ------------------------------------------------ | 1 | work | ------------------------------------------------ | 2 | home | ------------------------------------------------ and correspondingly tbl_address ------------------------------------------------------------------------------------- | address_id | address_description |address_type_id| user_id | ------------------------------------------------------------------------------------- | 1 | 123 main street | 1 | 100 | ------------------------------------------------------------------------------------- | 2 | 456 another street | 1 | 100 | ------------------------------------------------------------------------------------- | 3 | 789 long street | 2 | 200 | ------------------------------------------------------------------------------------- | 4 | 023 short street | 2 | 200 | ------------------------------------------------------------------------------------- Should the address type be modeled as an Entity or Value type? and Why? Is it OK for the Address Value object to hold a reference to the Entity AdressType (in case it was modeled as an entity)? Is this something feasible using Hibernate/NHibernate? If a user can change his home address, should I expose a User.updateHomeAddress(Address homeAddress) function on the User entity itself? How can I enforce that the client passes a Home address and not a work address in this case? (a sample implementation is most welcomed) If I want to get the User's home address via User.getHomeAddress() function, must I load the whole addresses array then loop it and check each for its type till I found the correct type then return it? Is there a more efficient way than this?

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• Help with design structure choice: Using classes or library of functions

  - by roverred

  So I have GUI Class that will call another class called ImageProcessor that contains a bunch functions that will perform image processing algorithms like edgeDetection, gaussianblur, contourfinding, contour map generations, etc. The GUI passes an image to ImageProcessor, which performs one of those algorithm on it and it returns the image back to the GUI to display. So essentially ImageProcessor is a library of independent image processing functions right now. It is called in the GUI like so Image image = ImageProcessor.EdgeDetection(oldImage); Some of the algorithms procedures require many functions, and some can be done in a single function or even one line. All these functions for the algorithms jam packed into ImageProcessor can be pretty messy, and ImageProcessor doesn't sound it should be a library. So I was thinking about making every algorithm be a class with a shared interface say IAlgorithm. Then I pass the IAlgorithm interface from the GUI to the ImageProcessor. public interface IAlgorithm{ public Image Process(); } public class ImageProcessor{ public Image Process(IAlgorithm TheAlgorithm){ return IAlgorithm.Process(); } } Calling in the GUI like so Image image = ImageProcessor.Process(new EdgeDetection(oldImage)); I think it makes sense in an object point of view, but the problem is I'll end up with some classes that are just one function. What do you think is a better design, or are they both crap and you have a much better idea? Thanks!

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• C++ HW - defining classes - objects that have objects of other class problem in header file (out of

  - by kitfuntastik

  This is my first time with much of this code. With this instancepool.h file below I get errors saying I can't use vector (line 14) or have instance& as a return type (line 20). It seems it can't use the instance objects despite the fact that I have included them. #ifndef _INSTANCEPOOL_H #define _INSTANCEPOOL_H #include "instance.h" #include <iostream> #include <string> #include <vector> #include <stdlib.h> using namespace std; class InstancePool { private: unsigned instances;//total number of instance objects vector<instance> ipp;//the collection of instance objects, held in a vector public: InstancePool();//Default constructor. Creates an InstancePool object that contains no Instance objects InstancePool(const InstancePool& original);//Copy constructor. After copying, changes to original should not affect the copy that was created. ~InstancePool();//Destructor unsigned getNumberOfInstances() const;//Returns the number of Instance objects the the InstancePool contains. const instance& operator[](unsigned index) const; InstancePool& operator=(const InstancePool& right);//Overloading the assignment operator for InstancePool. friend istream& operator>>(istream& in, InstancePool& ip);//Overloading of the >> operator. friend ostream& operator<<(ostream& out, const InstancePool& ip);//Overloading of the << operator. }; #endif Here is the instance.h : #ifndef _INSTANCE_H #define _INSTANCE_H ///////////////////////////////#include "instancepool.h" #include <iostream> #include <string> #include <stdlib.h> using namespace std; class Instance { private: string filenamee; bool categoryy; unsigned featuress; unsigned* featureIDD; unsigned* frequencyy; string* featuree; public: Instance (unsigned features = 0);//default constructor unsigned getNumberOfFeatures() const; //Returns the number of the keywords that the calling Instance object can store. Instance(const Instance& original);//Copy constructor. After copying, changes to the original should not affect the copy that was created. ~Instance() { delete []featureIDD; delete []frequencyy; delete []featuree;}//Destructor. void setCategory(bool category){categoryy = category;}//Sets the category of the message. Spam messages are represented with true and and legit messages with false.//easy bool getCategory() const;//Returns the category of the message. void setFileName(const string& filename){filenamee = filename;}//Stores the name of the file (i.e. “spam/spamsga1.txt”, like in 1st assignment) in which the message was initially stored.//const string& trick? string getFileName() const;//Returns the name of the file in which the message was initially stored. void setFeature(unsigned i, const string& feature, unsigned featureID,unsigned frequency) {//i for array positions featuree[i] = feature; featureIDD[i] = featureID; frequencyy[i] = frequency; } string getFeature(unsigned i) const;//Returns the keyword which is located in the ith position.//const string unsigned getFeatureID(unsigned i) const;//Returns the code of the keyword which is located in the ith position. unsigned getFrequency(unsigned i) const;//Returns the frequency Instance& operator=(const Instance& right);//Overloading of the assignment operator for Instance. friend ostream& operator<<(ostream& out, const Instance& inst);//Overloading of the << operator for Instance. friend istream& operator>>(istream& in, Instance& inst);//Overloading of the >> operator for Instance. }; #endif Also, if it is helpful here is instance.cpp: // Here we implement the functions of the class apart from the inline ones #include "instance.h" #include <iostream> #include <string> #include <stdlib.h> using namespace std; Instance::Instance(unsigned features) { //Constructor that can be used as the default constructor. featuress = features; if (features == 0) return; featuree = new string[featuress]; // Dynamic memory allocation. featureIDD = new unsigned[featuress]; frequencyy = new unsigned[featuress]; return; } unsigned Instance::getNumberOfFeatures() const {//Returns the number of the keywords that the calling Instance object can store. return featuress;} Instance::Instance(const Instance& original) {//Copy constructor. filenamee = original.filenamee; categoryy = original.categoryy; featuress = original.featuress; featuree = new string[featuress]; for(unsigned i = 0; i < featuress; i++) { featuree[i] = original.featuree[i]; } featureIDD = new unsigned[featuress]; for(unsigned i = 0; i < featuress; i++) { featureIDD[i] = original.featureIDD[i]; } frequencyy = new unsigned[featuress]; for(unsigned i = 0; i < featuress; i++) { frequencyy[i] = original.frequencyy[i];} } bool Instance::getCategory() const { //Returns the category of the message. return categoryy;} string Instance::getFileName() const { //Returns the name of the file in which the message was initially stored. return filenamee;} string Instance::getFeature(unsigned i) const { //Returns the keyword which is located in the ith position.//const string return featuree[i];} unsigned Instance::getFeatureID(unsigned i) const { //Returns the code of the keyword which is located in the ith position. return featureIDD[i];} unsigned Instance::getFrequency(unsigned i) const { //Returns the frequency return frequencyy[i];} Instance& Instance::operator=(const Instance& right) { //Overloading of the assignment operator for Instance. if(this == &right) return *this; delete []featureIDD; delete []frequencyy; delete []featuree; filenamee = right.filenamee; categoryy = right.categoryy; featuress = right.featuress; featureIDD = new unsigned[featuress]; frequencyy = new unsigned[featuress]; featuree = new string[featuress]; for(unsigned i = 0; i < featuress; i++) { featureIDD[i] = right.featureIDD[i]; } for(unsigned i = 0; i < featuress; i++) { frequencyy[i] = right.frequencyy[i]; } for(unsigned i = 0; i < featuress; i++) { featuree[i] = right.featuree[i]; } return *this; } ostream& operator<<(ostream& out, const Instance& inst) {//Overloading of the << operator for Instance. out << endl << "<message file=" << '"' << inst.filenamee << '"' << " category="; if (inst.categoryy == 0) out << '"' << "legit" << '"'; else out << '"' << "spam" << '"'; out << " features=" << '"' << inst.featuress << '"' << ">" <<endl; for (int i = 0; i < inst.featuress; i++) { out << "<feature id=" << '"' << inst.featureIDD[i] << '"' << " freq=" << '"' << inst.frequencyy[i] << '"' << "> " << inst.featuree[i] << " </feature>"<< endl; } out << "</message>" << endl; return out; } istream& operator>>(istream& in, Instance& inst) { //Overloading of the >> operator for Instance. string word; string numbers = ""; string filenamee2 = ""; bool categoryy2 = 0; unsigned featuress2; string featuree2; unsigned featureIDD2; unsigned frequencyy2; unsigned i; unsigned y; while(in >> word) { if (word == "<message") {//if at beginning of message in >> word;//grab filename word for (y=6; word[y]!='"'; y++) {//pull out filename from between quotes filenamee2 += word[y];} in >> word;//grab category word if (word[10] == 's') categoryy2 = 1; in >> word;//grab features word for (y=10; word[y]!='"'; y++) { numbers += word[y];} featuress2 = atoi(numbers.c_str());//convert string of numbers to integer Instance tempp2(featuress2);//make a temporary Instance object to hold values read in tempp2.setFileName(filenamee2);//set temp object to filename read in tempp2.setCategory(categoryy2); for (i=0; i<featuress2; i++) {//loop reading in feature reports for message in >> word >> word >> word;//skip two words numbers = "";//reset numbers string for (int y=4; word[y]!='"'; y++) {//grab feature ID numbers += word[y];} featureIDD2 = atoi(numbers.c_str()); in >> word;// numbers = ""; for (int y=6; word[y]!='"'; y++) {//grab frequency numbers += word[y];} frequencyy2 = atoi(numbers.c_str()); in >> word;//grab actual feature string featuree2 = word; tempp2.setFeature(i, featuree2, featureIDD2, frequencyy2); }//all done reading in and setting features in >> word;//read in last part of message : </message> inst = tempp2;//set inst (reference) to tempp2 (tempp2 will be destroyed at end of function call) return in; } } } and instancepool.cpp: // Here we implement the functions of the class apart from the inline ones #include "instancepool.h" #include "instance.h" #include <iostream> #include <string> #include <vector> #include <stdlib.h> using namespace std; InstancePool::InstancePool()//Default constructor. Creates an InstancePool object that contains no Instance objects { instances = 0; ipp.clear(); } InstancePool::~InstancePool() { ipp.clear();} InstancePool::InstancePool(const InstancePool& original) {//Copy constructor. instances = original.instances; for (int i = 0; i<instances; i++) { ipp.push_back(original.ipp[i]); } } unsigned InstancePool::getNumberOfInstances() const {//Returns the number of Instance objects the the InstancePool contains. return instances;} const Instance& InstancePool::operator[](unsigned index) const {//Overloading of the [] operator for InstancePool. return ipp[index];} InstancePool& InstancePool::operator=(const InstancePool& right) {//Overloading the assignment operator for InstancePool. if(this == &right) return *this; ipp.clear(); instances = right.instances; for(unsigned i = 0; i < instances; i++) { ipp.push_back(right.ipp[i]); } return *this; } istream& operator>>(istream& in, InstancePool& ip) {//Overloading of the >> operator. ip.ipp.clear(); string word; string numbers; int total;//int to hold total number of messages in collection while(in >> word) { if (word == "<messagecollection"){ in >> word;//reads in total number of all messages for (int y=10; word[y]!='"'; y++){ numbers = ""; numbers += word[y]; } total = atoi(numbers.c_str()); for (int x = 0; x<total; x++) {//do loop for each message in collection in >> ip.ipp[x];//use instance friend function and [] operator to fill in values and create Instance objects and read them intot he vector } } } } ostream& operator<<(ostream& out, const InstancePool& ip) {//Overloading of the << operator. out << "<messagecollection messages=" << '"' << '>' << ip.instances << '"'<< endl << endl; for (int z=0; z<ip.instances; z++) { out << ip[z];} out << endl<<"</messagecollection>\n"; } This code is currently not writing to files correctly either at least, I'm sure it has many problems. I hope my posting of so much is not too much, and any help would be very much appreciated. Thanks!

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• Inheritance Mapping Strategies with Entity Framework Code First CTP5: Part 2 – Table per Type (TPT)

  - by mortezam

  In the previous blog post you saw that there are three different approaches to representing an inheritance hierarchy and I explained Table per Hierarchy (TPH) as the default mapping strategy in EF Code First. We argued that the disadvantages of TPH may be too serious for our design since it results in denormalized schemas that can become a major burden in the long run. In today’s blog post we are going to learn about Table per Type (TPT) as another inheritance mapping strategy and we'll see that TPT doesn’t expose us to this problem. Table per Type (TPT)Table per Type is about representing inheritance relationships as relational foreign key associations. Every class/subclass that declares persistent properties—including abstract classes—has its own table. The table for subclasses contains columns only for each noninherited property (each property declared by the subclass itself) along with a primary key that is also a foreign key of the base class table. This approach is shown in the following figure: For example, if an instance of the CreditCard subclass is made persistent, the values of properties declared by the BillingDetail base class are persisted to a new row of the BillingDetails table. Only the values of properties declared by the subclass (i.e. CreditCard) are persisted to a new row of the CreditCards table. The two rows are linked together by their shared primary key value. Later, the subclass instance may be retrieved from the database by joining the subclass table with the base class table. TPT Advantages The primary advantage of this strategy is that the SQL schema is normalized. In addition, schema evolution is straightforward (modifying the base class or adding a new subclass is just a matter of modify/add one table). Integrity constraint definition are also straightforward (note how CardType in CreditCards table is now a non-nullable column). Another much more important advantage is the ability to handle polymorphic associations (a polymorphic association is an association to a base class, hence to all classes in the hierarchy with dynamic resolution of the concrete class at runtime). A polymorphic association to a particular subclass may be represented as a foreign key referencing the table of that particular subclass. Implement TPT in EF Code First We can create a TPT mapping simply by placing Table attribute on the subclasses to specify the mapped table name (Table attribute is a new data annotation and has been added to System.ComponentModel.DataAnnotations namespace in CTP5): public abstract class BillingDetail {     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } } [Table("BankAccounts")] public class BankAccount : BillingDetail {     public string BankName { get; set; }     public string Swift { get; set; } } [Table("CreditCards")] public class CreditCard : BillingDetail {     public int CardType { get; set; }     public string ExpiryMonth { get; set; }     public string ExpiryYear { get; set; } } public class InheritanceMappingContext : DbContext {     public DbSet<BillingDetail> BillingDetails { get; set; } } If you prefer fluent API, then you can create a TPT mapping by using ToTable() method: protected override void OnModelCreating(ModelBuilder modelBuilder) {     modelBuilder.Entity<BankAccount>().ToTable("BankAccounts");     modelBuilder.Entity<CreditCard>().ToTable("CreditCards"); } Generated SQL For QueriesLet’s take an example of a simple non-polymorphic query that returns a list of all the BankAccounts: var query = from b in context.BillingDetails.OfType<BankAccount>() select b; Executing this query (by invoking ToList() method) results in the following SQL statements being sent to the database (on the bottom, you can also see the result of executing the generated query in SQL Server Management Studio): Now, let’s take an example of a very simple polymorphic query that requests all the BillingDetails which includes both BankAccount and CreditCard types: projects some properties out of the base class BillingDetail, without querying for anything from any of the subclasses: var query = from b in context.BillingDetails             select new { b.BillingDetailId, b.Number, b.Owner }; -- var query = from b in context.BillingDetails select b; This LINQ query seems even more simple than the previous one but the resulting SQL query is not as simple as you might expect: -- As you can see, EF Code First relies on an INNER JOIN to detect the existence (or absence) of rows in the subclass tables CreditCards and BankAccounts so it can determine the concrete subclass for a particular row of the BillingDetails table. Also the SQL CASE statements that you see in the beginning of the query is just to ensure columns that are irrelevant for a particular row have NULL values in the returning flattened table. (e.g. BankName for a row that represents a CreditCard type) TPT ConsiderationsEven though this mapping strategy is deceptively simple, the experience shows that performance can be unacceptable for complex class hierarchies because queries always require a join across many tables. In addition, this mapping strategy is more difficult to implement by hand— even ad-hoc reporting is more complex. This is an important consideration if you plan to use handwritten SQL in your application (For ad hoc reporting, database views provide a way to offset the complexity of the TPT strategy. A view may be used to transform the table-per-type model into the much simpler table-per-hierarchy model.) SummaryIn this post we learned about Table per Type as the second inheritance mapping in our series. So far, the strategies we’ve discussed require extra consideration with regard to the SQL schema (e.g. in TPT, foreign keys are needed). This situation changes with the Table per Concrete Type (TPC) that we will discuss in the next post. References ADO.NET team blog Java Persistence with Hibernate book a { text-decoration: none; } a:visited { color: Blue; } .title { padding-bottom: 5px; font-family: Segoe UI; font-size: 11pt; font-weight: bold; padding-top: 15px; } .code, .typeName { font-family: consolas; } .typeName { color: #2b91af; } .padTop5 { padding-top: 5px; } .padTop10 { padding-top: 10px; } p.MsoNormal { margin-top: 0in; margin-right: 0in; margin-bottom: 10.0pt; margin-left: 0in; line-height: 115%; font-size: 11.0pt; font-family: "Calibri" , "sans-serif"; }

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• How to determine the data type of a CvMat

  - by Chris

  When using the CvMat type, the type of data is crucial to keeping your program running. For example, depending on whether your data is type float or unsigned char, you would choose one of these two commands: cvmGet(mat, row, col); cvGetReal2D(mat, row, col); Is there a universal approach to this? If the wrong data type matrix is passed to these calls, they crash at runtime. This is becoming an issue, since a function I have defined is getting passed several different types of matrices. How do you determine the data type of a matrix so you can always access its data? I tried using the "type()" function as such. CvMat* tmp_ptr = cvCreateMat(t_height,t_width,CV_8U); std::cout << "type = " << tmp_ptr->type() << std::endl; This does not compile, saying "term does not evaluate to a function taking 0 arguments". If I remove the brackets after the word type, I get a type of 1111638032 EDIT minimal application that reproduces this... int main( int argc, char** argv ) { CvMat *tmp2 = cvCreateMat(10,10, CV_32FC1); std::cout << "tmp2 type = " << tmp2->type << " and CV_32FC1 = " << CV_32FC1 << " and " << (tmp2->type == CV_32FC1) << std::endl; } Output: tmp2 type = 1111638021 and CV_32FC1 = 5 and 0

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• Type errors when using same name

  - by lykimq

  I have 3 files: 1) cpf0.ml type string = char list type url = string type var = string type name = string type symbol = | Symbol_name of name 2) problem.ml: type symbol = | Ident of string 3) test.ml open Problem;; open Cpf0;; let symbol b = function | Symbol_name n -> Ident n When I combine test.ml: ocamlc -c test.ml. I received an error: This expression has type Cpf0.name = char list but an expression was expected of type string Could you please help me to correct it? Thank you very much EDIT: Thank you for your answer. I want to explain more about these 3 files: Because I am working with extraction in Coq to Ocaml type: cpf0.ml is generated from cpf.v : Require Import String. Definition string := string. Definition name := string. Inductive symbol := | Symbol_name : name -> symbol. The code extraction.v: Set Extraction Optimize. Extraction Language Ocaml. Require ExtrOcamlBasic ExtrOcamlString. Extraction Blacklist cpf list. where ExtrOcamlString I opened: open Cpf0;; in problem.ml, and I got a new problem because in problem.ml they have another definition for type string This expression has type Cpf0.string = char list but an expression was expected of type Util.StrSet.elt = string Here is a definition in util.ml defined type string: module Str = struct type t = string end;; module StrOrd = Ord.Make (Str);; module StrSet = Set.Make (StrOrd);; module StrMap = Map.Make (StrOrd);; let set_add_chk x s = if StrSet.mem x s then failwith (x ^ " already declared") else StrSet.add x s;; I was trying to change t = string to t = char list, but if I do that I have to change a lot of function it depend on (for example: set_add_chk above). Could you please give me a good idea? how I would do in this case.

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• SQL SERVER – LCK_M_XXX – Wait Type – Day 15 of 28

  - by pinaldave

  Locking is a mechanism used by the SQL Server Database Engine to synchronize access by multiple users to the same piece of data, at the same time. In simpler words, it maintains the integrity of data by protecting (or preventing) access to the database object. From Book On-Line: LCK_M_BU Occurs when a task is waiting to acquire a Bulk Update (BU) lock. LCK_M_IS Occurs when a task is waiting to acquire an Intent Shared (IS) lock. LCK_M_IU Occurs when a task is waiting to acquire an Intent Update (IU) lock. LCK_M_IX Occurs when a task is waiting to acquire an Intent Exclusive (IX) lock. LCK_M_S Occurs when a task is waiting to acquire a Shared lock. LCK_M_SCH_M Occurs when a task is waiting to acquire a Schema Modify lock. LCK_M_SCH_S Occurs when a task is waiting to acquire a Schema Share lock. LCK_M_SIU Occurs when a task is waiting to acquire a Shared With Intent Update lock. LCK_M_SIX Occurs when a task is waiting to acquire a Shared With Intent Exclusive lock. LCK_M_U Occurs when a task is waiting to acquire an Update lock. LCK_M_UIX Occurs when a task is waiting to acquire an Update With Intent Exclusive lock. LCK_M_X Occurs when a task is waiting to acquire an Exclusive lock. LCK_M_XXX Explanation: I think the explanation of this wait type is the simplest. When any task is waiting to acquire lock on any resource, this particular wait type occurs. The common reason for the task to be waiting to put lock on the resource is that the resource is already locked and some other operations may be going on within it. This wait also indicates that resources are not available or are occupied at the moment due to some reasons. There is a good chance that the waiting queries start to time out if this wait type is very high. Client application may degrade the performance as well. You can use various methods to find blocking queries: EXEC sp_who2 SQL SERVER – Quickest Way to Identify Blocking Query and Resolution – Dirty Solution DMV – sys.dm_tran_locks DMV – sys.dm_os_waiting_tasks Reducing LCK_M_XXX wait: Check the Explicit Transactions. If transactions are very long, this wait type can start building up because of other waiting transactions. Keep the transactions small. Serialization Isolation can build up this wait type. If that is an acceptable isolation for your business, this wait type may be natural. The default isolation of SQL Server is ‘Read Committed’. One of my clients has changed their isolation to “Read Uncommitted”. I strongly discourage the use of this because this will probably lead to having lots of dirty data in the database. Identify blocking queries mentioned using various methods described above, and then optimize them. Partition can be one of the options to consider because this will allow transactions to execute concurrently on different partitions. If there are runaway queries, use timeout. (Please discuss this solution with your database architect first as timeout can work against you). Check if there is no memory and IO-related issue using the following counters: Checking Memory Related Perfmon Counters SQLServer: Memory Manager\Memory Grants Pending (Consistent higher value than 0-2) SQLServer: Memory Manager\Memory Grants Outstanding (Consistent higher value, Benchmark) SQLServer: Buffer Manager\Buffer Hit Cache Ratio (Higher is better, greater than 90% for usually smooth running system) SQLServer: Buffer Manager\Page Life Expectancy (Consistent lower value than 300 seconds) Memory: Available Mbytes (Information only) Memory: Page Faults/sec (Benchmark only) Memory: Pages/sec (Benchmark only) Checking Disk Related Perfmon Counters Average Disk sec/Read (Consistent higher value than 4-8 millisecond is not good) Average Disk sec/Write (Consistent higher value than 4-8 millisecond is not good) Average Disk Read/Write Queue Length (Consistent higher value than benchmark is not good) Read all the post in the Wait Types and Queue series. Note: The information presented here is from my experience and there is no way that I claim it to be accurate. I suggest reading Book OnLine for further clarification. All the discussion of Wait Stats in this blog is generic and varies from system to system. It is recommended that you test this on a development server before implementing it to a production server. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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• Is it appropriate for a class to only be a collection of information with no logic?

  - by qegal

  Say I have a class Person that has instance variables age, weight, and height, and another class Fruit that has instance variables sugarContent and texture. The Person class has no methods save setters and getters, while the Fruit class has both setters and getters and logic methods like calculateSweetness. Is the Fruit class the type of class that is better practice than the Person class. What I mean by this is that the Person class seems like it doesn't have much purpose; it exists solely to organize data, while the Fruit class organizes data and actually contains methods for logic.

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• Keyboard "type ahead" in CRUD web apps?

  - by user61852

  In some data entry contexts, I've seen data typists, type really fast and know so well the app they use, and have a mechanic quality in their work so that they can "type ahead", ie continue typing and "tab-bing" and "enter-ing" faster than the display updates, so that in many occasions they are typing in the data for the next form before it draws itself. Then when this next entry form appears, their keystrokes fill the text boxes and they continue typing, selecting etc. In contexts like this, this speed is desirable, since this persons are really productive. I think this "type ahead of time" is only possible in desktop apps, but I may be wrong. My question is whether this way of handling the keyboard buffer (which in desktop apps require no extra programming) is achievable in web apps, or is this impossible because of the way web apps work, handle sessions, etc (network latency and the overhead of generating new web pages ) ?

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• SQL Server and the XML Data Type : Data Manipulation

  The introduction of the xml data type, with its own set of methods for processing xml data, made it possible for SQL Server developers to create columns and variables of the type xml. Deanna Dicken examines the modify() method, which provides for data manipulation of the XML data stored in the xml data type via XML DML statements. Too many SQL Servers to keep up with?Download a free trial of SQL Response to monitor your SQL Servers in just one intuitive interface."The monitoringin SQL Response is excellent." Mike Towery.

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• CSS3 - "connecting" 2 classes animation [closed]

  - by Nave Tseva

  I have this CSS +HTML code: <!DOCTYPE HTML> <html> <head> <meta http-equiv="content-type" content="text/html; charset=UTF-8" /> <title>What</title> <style type="text/css"> #page { width: 900px; padding: 0px; margin: 0 auto; direction: rtl; position: relative; } #box1 { position: relative; width: 500px; border: 1px solid black; box-shadow: -3px 8px 34px #808080; border-radius: 20px; box-shadow: -8px 5px 5px #888888; right: 300px; top: 250px; height: 150px; -webkit-transition: all 1s; font-size: large; color: Black; padding: 10px; background: #D0D0D0; opacity: 0; } @-webkit-keyframes myFirst { 0% { right: 300px; top: 150px; background: #D0D0D0; opacity: 0; } 100% { background: #909090; ; right: 300px; top: 200px; opacity: 1; } } #littlebox1 { top: 200px; position: absolute; display: inline-block; } .littlebox1-sentence { font-size: large; padding-bottom: 15px; padding-top: 15px; padding-left: 25px; padding-right: 10px; background: #D0D0D0; border-radius: 10px; -webkit-transition: background .25s ease-in-out; } #littlebox1:hover ~ #box1 { -webkit-transition: all 0s; background: #909090;; right: 300px; top: 200px; -webkit-animation: myFirst 1s; -webkit-animation-fill-mode: initial; opacity: 1; } .littlebox1-sentence:hover { background: #909090; } .littlebox1-sentence:hover + .triangle { border-right: 50px solid #909090; } .triangle { position: relative; width: 0; height: 0; border-right: 50px solid #D0D0D0; border-top: 24px solid transparent; border-bottom: 24px solid transparent; right: 160px; -webkit-transition: border-right .25s ease-in-out; } .triangle:hover { border-right:50px solid #909090; } </style> <script src="//ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script> <script> $(function() { $('.littlebox1-sentence').hover(function() { $(this).css('background', '#909090'); $('.triangle').css('border-right', '50px solid #909090'); }); </script> <script> $(function() { $('.triangle').hover(function() { $(this).css('border-right', '50px solid #909090'); $('.littlebox1-sentence').css('background', '#909090'); }); </script> </head> <body dir="rtl"> <div id="page"> <div id="littlebox1" class="littlebox1-sentence">put your mouse here</div><div id="littlebox1" class="triangle"> </div> <div id="box1"> </div> </div> </body> </html> Live example you will find here: http://jsfiddle.net/FLe4g/12/ The problem here that something here wrong in the second jquery code. I want that every time that I put the mouse on the box, or on the triangke they both will change ther color together. when I put the mouse on the box it works fine, but when I put the mouse on the triangle it don't work. Any suggestions how to fix this code?

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• input type="email"

  - by Charles

  I have a form where I ask for email addresses. Usually I'd use <input type="email" ...> but I want to allow a user to type foo rather than [email protected] in the (likely) case that they are using an @mycompany.com email address. Is there a way to get around the validation (if format matches this regex, accept; otherwise, validate normally), or should I just use <input type="text" ...> and ignore the semantics and so forth?

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• How to mock ISerializable classes with Moq?

  - by asmois

  Hi there, I'm completly new to Moq and now trying to create a mock for System.Assembly class. I'm using this code: var mockAssembly = new Mock<Assembly>(); mockAssembly.Setup( x => x.GetTypes() ).Returns( new Type[] { typeof( Type1 ), typeof( Type2 ) } ); But when I run tests I get next exception: System.ArgumentException : The type System.Reflection.Assembly implements ISerializable, but failed to provide a deserialization constructor Stack Trace: at Castle.DynamicProxy.Generators.BaseProxyGenerator.VerifyIfBaseImplementsGet­ObjectData(Type baseType) at Castle.DynamicProxy.Generators.ClassProxyGenerator.GenerateCode(Type[] interfaces, ProxyGenerationOptions options) at Castle.DynamicProxy.DefaultProxyBuilder.CreateClassProxy(Type classToProxy, Type[] additionalInterfacesToProxy, ProxyGenerationOptions options) at Castle.DynamicProxy.ProxyGenerator.CreateClassProxy(Type classToProxy, Type[] additionalInterfacesToProxy, ProxyGenerationOptions options, Object[] constructorArguments, IInterceptor[] interceptors) at Moq.Proxy.CastleProxyFactory.CreateProxy[T](ICallInterceptor interceptor, Type[] interfaces, Object[] arguments) at Moq.Mock`1.<InitializeInstance>b__0() at Moq.PexProtector.Invoke(Action action) at Moq.Mock`1.InitializeInstance() at Moq.Mock`1.OnGetObject() at Moq.Mock`1.get_Object() Could you reccomend me the right way to mock ISerializable classes (like System.Assembly) with Moq. Thanks in advance!

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• C#: Dynamically instantiate different classes in the same statement?

  - by C. Griffin

  Here is a simplified version of what I'm trying to do: Without having multiple if..else clauses and switch blocks, can I mimic the behavior of Javascript's eval() shudder to instantiate a class in C#? // Determine report orientation -- Portrait or Landscape // There are 2 differently styled reports (beyond paper orientation) string reportType = "Portrait"; GenericReport report; report = new eval(reportType + "Report()"); // Resolves to PortraitReport() The need stems from the fact that I have 6 types of Crystal Reports (that do the same thing, but look drastically different) for 50 states. There are 3 styles each, rather than entertain the notion of a giant switch block with nested if..else statements determining which of 900 reports to use, I was hoping for an eval-like solution.

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• C# - Which is more efficient and thread safe? static or instant classes?

  - by Soni Ali

  Consider the following two scenarios: //Data Contract public class MyValue { } Scenario 1: Using a static helper class. public class Broker { private string[] _userRoles; public Broker(string[] userRoles) { this._userRoles = userRoles; } public MyValue[] GetValues() { return BrokerHelper.GetValues(this._userRoles); } } static class BrokerHelper { static Dictionary<string, MyValue> _values = new Dictionary<string, MyValue>(); public static MyValue[] GetValues(string[] rolesAllowed) { return FilterForRoles(_values, rolesAllowed); } } Scenario 2: Using an instance class. public class Broker { private BrokerService _service; public Broker(params string[] userRoles) { this._service = new BrokerService(userRoles); } public MyValue[] GetValues() { return _service.GetValues(); } } class BrokerService { private Dictionary<string, MyValue> _values; private string[] _userRoles; public BrokerService(string[] userRoles) { this._userRoles = userRoles; this._values = new Dictionary<string, MyValue>(); } public MyValue[] GetValues() { return FilterForRoles(_values, _userRoles); } } Which of the [Broker] scenarios will scale best if used in a web environment with about 100 different roles and over a thousand users. NOTE: Feel free to sugest any alternative approach.

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• How many times can classes be nested within a class?

  - by Kushal Paudyal

  I came across this questions on one of the online Java Tests. The options were 4,5,8 and any number of times. I have only used one inner class, but have never tried multiple ones. I was wondering if anyone knows the answer.

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• How to make and check a request with content-type as 'application/json'?

  - by kranthi

  hi all, In my asp.net page I have a webmethod which will return data in json.I would like to run this method only when the http request content-type is 'application/json'.I do not understand how do I make a request with content-type as 'application/json' and how to check if the request content-type is 'application/json'? Please help.. Thanks.

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• How to use a data type (table) defined in another database in SQL2k8?

  - by Victor Rodrigues

  I have a Table Type defined in a database. It is used as a table-valued parameter in a stored procedure. I would like to call this procedure from another database, and in order to pass the parameter, I need to reference this defined type. But when I do DECLARE @table dbOtherDatabase.dbo.TypeName , it tells me that The type name 'dbOtherDatabase.dbo.TypeName' contains more than the maximum number of prefixes. The maximum is 1. How could I reference this table type?

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• I'm new to OOP/PHP. What's the practicality of visibility and extensibility in classes?

  - by marcdev

  I'm obviously brand new to these concepts. I just don't understand why you would limit access to properties or methods. It seems that you would just write the code according to intended results. Why would you create a private method instead of simply not calling that method? Is it for iterative object creation (if I'm stating that correctly), a multiple developer situation (don't mess up other people's work), or just so you don't mess up your own work accidentally?

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