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• In Java it seems Public constructors are always a bad coding practice

  - by Adam Gent

  This maybe a controversial question and may not be suited for this forum (so I will not be insulted if you choose to close this question). It seems given the current capabilities of Java there is no reason to make constructors public ... ever. Friendly, private, protected are OK but public no. It seems that its almost always a better idea to provide a public static method for creating objects. Every Java Bean serialization technology (JAXB, Jackson, Spring etc...) can call a protected or private no-arg constructor. My questions are: I have never seen this practice decreed or written down anywhere? Maybe Bloch mentions it but I don't own is book. Is there a use case other than perhaps not being super DRY that I missed? EDIT: I explain why static methods are better. .1. For one you get better type inference. For example See Guava's http://code.google.com/p/guava-libraries/wiki/CollectionUtilitiesExplained .2. As a designer of the class you can later change what is returned with a static method. .3. Dealing with constructor inheritance is painful especially if you have to pre-calculate something.

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• Managing inverse relationships without CoreData

  - by Nathaniel Martin

  This is a question for Objective-J/Cappuccino, but I added the cocoa tag since the frameworks are so similar. One of the downsides of Cappuccino is that CoreData hasn't been ported over yet, so you have to make all your model objects manually. In CoreData, your inverse relationships get managed automatically for you... if you add an object to a to-many relationship in another object, you can traverse the graph in both directions. Without CoreData, is there any clean way to setup those inverse relationships automatically? For a more concrete example, let's take the typical Department and Employees example. To use rails terminology, a Department object has-many Employees, and an Employee belongs-to a Department. So our Department model has an NSMutableSet (or CPMutableSet ) "employees" that contains a set of Employees, and our Employee model has a variable "department" that points back to the Department model that owns it. Is there an easy way to make it so that, when I add a new Employee model into the set, the inverse relationship (employee.department) automatically gets set? Or the reverse: If I set the department model of an employee, then it automatically gets added to that department's employee set? Right know I'm making an object, "ValidatedModel" that all my models subclass, which adds a few methods that setup the inverse relationships, using KVO. But I'm afraid that I'm doing a lot of pointless work, and that there's already an easier way to do this. Can someone put my concerns to rest?

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• Trying to create XPath from this HTML snippet

  - by doneright

  I have played for a while writing XPath but am unable to come up with exactly what I want. I'm trying to write XPath for link(click1 and click2 in code snippet below) based on known text(myidentity in code snippet below). Can someone take a look into and suggest possible solution? HTML code snippet: <div class="abc"> <a onclick="mycontroller.goto('xx','yy'); return false;" href="#"> <img src="images/controls/inheritance.gif"/> </a> myidentity <span> <a onclick="mycontroller.goto('xx','yy'); return false;" href="#">click1</a> <a onclick="mycontroller.goto('xx','yy'); return false;" href="#">click2</a> </span> </div>

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• WCF code generation for large/complex schema (HR-XML/OAGIS) - is there an alternative?

  - by Sasha Borodin

  Hello, and thank you for reading. I am implementing a WCF Service based on a predefined specification (HR-XML 3.0). As such, I am starting with the schema, and working my way back to code. There are a number of large Schema documents (which import yet more Schema documents) related to my implementation, provided by this specification. I am able to generate code using xsd.exe, by supplying the "main" and "supporting" xsd files as arguments. But there are several issues, and I am wondering if this is the right approach. there are litterally hundreds of classes - the code file is half a meg in size duplicate classes (ex. Type, Type1 - which both represent the same type) there are classes declared as inheriting from a base class, but that base class is not generated/defined I understand that there are limitations to the types of Schema supported by svcutil.exe/xsd.exe when targeting the DataContractSerializer and even XmlSerializer. My question is two-fold: Are code generation "issues" fairly common when dealing with larger, modular xsd files? Has anyone had success with generating data contracts from OAGIS or HR-XML schema? Given the above issues, are there better approaches to this task, avoiding generating code and working with concrete objects? Does it make better sence to read and compose a SOAP message directly, while still taking advantage of the rest of the WCF framework? I understand that I am loosing the convenience of working with .NET objects, and the framekwork-provided (de)serialization; given these losses, would it still be advantageous to base my Service on WCF? Is there some "middle ground" between working with .NET types and pure XML? Thank you very much! -Sasha Borodin DFWHC.org

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• Using StructureMap to create classes by a name?

  - by Bevan

  How can I use StructureMap to resolve to an appropriate implementation of an interface based on a name stored in an attribute? In my project, I have many different kinds of widgets, each descending from IWidget, and each decorated with an attribute specifying the kind of associated element. To illustrate: [Configuration("header")] public class HeaderWidget : IWidget { } [Configuration("linegraph")] public class LineGraphWidget : IWidget { } When processing my (XML) configuration file, I want to obtain an instance of the appropriate concrete class based on the name of the element I'm processing. public IWidget CreateWidget(XElement definition) { var kind = definition.Name.LocalName; var widget = // What goes here? widget.Configure(definition); return widget; } Each definition should result in a different widget being created - I don't need or want the instances to be shared. In the past I've written plenty of code to do this kind of thing manually, including writing a custom "roll-your-own" IoC container for one project. However, one of my goals with this project is to become proficient with StructureMap instead of reinventing the wheel. I think I've already managed to set up automatic scanning of assemblies so that StructureMap knows about all my IWidget implementations: public class WidgetRegistration : Registry { public WidgetRegistration() { Scan( scanner => { scanner.AssembliesFromApplicationBaseDirectory(); scanner.AddAllTypesOf<IWidget>(); }); } } However, this isn't registering the names of my widgets with StructureMap. What do I need to add to make my scenario work? (While I am trying to use StructureMap in this project, an answer showing me how to solve this problem with a different DI/IoC tool would still be valuable.)

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• C++: Calling class functions within a switch

  - by user1446002

  i've been trying to study for my finals by practicing classes and inheritance, this is what I've come up with so far for inheritance and such however I'm unsure how to fix the error occuring below. #include<iostream> #include<iomanip> #include<cmath> #include<string.h> using namespace std; //BASE CLASS DEFINITION class hero { protected: string name; string mainAttr; int xp; double hp; double mana; double armour; int range; double attkDmg; bool attkType; public: void dumpData(); void getName(); void getMainAttr(); void getAttkData(); void setAttkData(string); void setBasics(string, string, double, double, double); void levelUp(); }; //CLASS FUNCTIONS void hero::dumpData() { cout << "Name: " << name << endl; cout << "Main Attribute: " << mainAttr << endl; cout << "XP: " << xp << endl; cout << "HP: " << hp << endl; cout << "Mana: " << mana << endl; cout << "Armour: " << armour << endl; cout << "Attack Range: " << range << endl; cout << "Attack Damage: " << attkDmg << endl; cout << "Attack Type: " << attkType << endl << endl; } void hero::getName() { cout << "Name: " << name << endl; } void hero::getMainAttr() { cout << "Main Attribute: " << mainAttr << endl; } void hero::getAttkData() { cout << "Attack Range: " << range << endl; cout << "Attack Damage: " << attkDmg << endl; cout << "Attack Type: " << attkType << endl; } void hero::setAttkData(string attr) { int choice = 0; if (attr == "Strength") { choice = 1; } if (attr == "Agility") { choice = 2; } if (attr == "Intelligence") { choice = 3; } switch (choice) { case 1: range = 128; attkDmg = 80.0; attkType = 0; break; case 2: range = 350; attkDmg = 60.0; attkType = 0; break; case 3: range = 600; attkDmg = 35.0; attkType = 1; break; default: break; } } void hero::setBasics(string heroName, string attribute, double health, double mp, double armourVal) { name = heroName; mainAttr = attribute; hp = health; mana = mp; armour = armourVal; } void hero::levelUp() { xp = 0; hp = hp + (hp * 0.1); mana = mana + (mana * 0.1); armour = armour + ((armour*0.1) + 1); attkDmg = attkDmg + (attkDmg * 0.05); } //INHERITED CLASS DEFINITION class neutHero : protected hero { protected: string drops; int xpGain; public: int giveXP(int); void dropItems(); }; //INHERITED CLASS FUNCTIONS int neutHero::giveXP(int exp) { xp += exp; } void neutHero::dropItems() { cout << name << " has dropped the following items: " << endl; cout << drops << endl; } /* END OF OO! */ //FUNCTION PROTOTYPES void dispMenu(); int main() { int exit=0, choice=0, mainAttrChoice=0, heroCreated=0; double health, mp, armourVal; string heroName, attribute; do { dispMenu(); cin >> choice; switch (choice) { case 1: system("cls"); cout << "Please enter your hero name: "; cin >> heroName; cout << "\nPlease enter your primary attribute\n"; cout << "1. Strength\n" << "2. Agility\n" << "3. Intelligence\n"; cin >> mainAttrChoice; switch (mainAttrChoice) { case 1: attribute = "Strength"; health = 750; mp = 150; armourVal = 2; break; case 2: attribute = "Agility"; health = 550; mp = 200; armourVal = 6; break; case 3: attribute = "Intelligence"; health = 450; mp = 450; armourVal = 1; break; default: cout << "Choice invalid, please try again."; exit = 1; break; hero player; player.setBasics(heroName, attribute, health, mp, armourVal); player.setAttkData(attribute); heroCreated=1; system("cls"); cout << "Your hero has been created!\n\n"; player.dumpData(); system("pause"); break; } case 2: system("cls"); if (heroCreated == 1) { cout << "Your hero has been detailed below.\n\n"; **player.dumpData(); //ERROR OCCURS HERE !** system("pause"); } else { cout << "You have not created a hero please exit this prompt " "and press 1 on the menu to create a hero."; } break; case 3: system("cls"); cout << "Still Under Development"; system("pause"); break; case 4: system("cls"); exit = 1; break; default: cout << "Your command has not been recognised, please try again.\n"; system("pause"); break; } } while (exit != 1); system("pause"); return 0; } void dispMenu() { system("cls"); cout << "1. Create New Hero\n" "2. View Current Hero\n" "3. Fight Stuff\n" "4. Exit\n\n" "Enter your choice: "; } However upon compilation I get the following errors: 220 `player' undeclared (first use this function) Unsure exactly how to fix it as I've only recently started using OO approach. The error has a comment next to it above and is in case 2 in the main. Cheers guys.

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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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• C/C++ Control Structure Limitations?

  - by STingRaySC

  I have heard of a limitation in VC++ (not sure which version) on the number of nested if statements (somewhere in the ballpark of 300). The code was of the form: if (a) ... else if (b) ... else if (c) ... ... I was surprised to find out there is a limit to this sort of thing, and that the limit is so small. I'm not looking for comments about coding practice and why to avoid this sort of thing altogether. Here's a list of things that I'd imagine could have some limitation: Number of functions in a scope (global, class, or namespace). Number of expressions in a single statement (e.g., compound conditionals). Number of cases in a switch. Number of parameters to a function. Number of classes in a single hierarchy (either inheritance or containment). What other control structures/language features have limits such as this? Do the language standards say anything about these limits (perhaps minimum requirements for an implementation)? Has anyone run into a particular language limitation like this with a particular compiler/implementation? EDIT: Please note that the above form of if statements is indeed "nested." It is equivalent to: if (a) { //... } else { if (b) { //... } else { if (c) { //... } else { //... } } }

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• Free utility which runs in Linux to create a UML class diagram from Java source files

  - by DeletedAccount

  I prefer to jot down UML-diagrams on paper and then implement them using Java. It would be nice to have a utility which could create UML-diagrams for me which I may share on-line and include in the digital documentation. In other words: I want to create UML diagrams from Java source code. The utility must be able to: Run in Linux. Handle Generics, i.e show List<Foo correctly in parameters and return type. Show class inheritance and interface implementations. It's nice if the utility is able to: Run in Windows and Mac OS X. Display enums in some nice manner. Generate output in a diagram format which I may modify using some other utility. Run from the command line. Restrict the UML generation to a set of packages which I may specify. Handle classes/interfaces which are not part of my source code. It could include the first class/interface which is external in the UML diagram. Perhaps in another color to indicate it being a library/framework created by someone else. Focuses on this task and doesn't try to solve the whole issue of documentation.

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• Mercurial: applying changes one by one to resolve merging issues

  - by Webinator

  I recently tried to merge a series of changeset and encountered a huge number of merging issues. Hence I'd like to to try to apply each changeset, in order, one by one, in order to make the merging issues easier to manage. I'll give an example with 4 problematic changesets (514,515,516 and 517) [in my real case, I've got a bit more than that] o changeset: 517 | o changeset: 516 | o changeset: 515 | o changeset: 514 | | | @ changeset: 513 | | | o changeset: 512 | | | o | | | o | | | o |/ | | o changeset 508 Note that I've got clones of my repos before pulling the problematic changesets. When I pull the 4 changesets and try a merge, things are too complicated to resolve. So I wanted to pull only changeset 514, then merge. Then once I solve the merging issue, pull only changeset 515 and apply it, etc. (I know the numbering shall change, this is not my problem here). How am I supposed to do that, preferably without using any extension? (because I'd like to understand Mercurial and what I'm doing better). Is the way to go generate a patch between 508 and 514 and apply that patch? (if so, how would I generate that patch) Answers including concrete command-line example(s) most welcome :)

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• How do I iterate over a collection that is in an object passed as parameter in a jasper report?

  - by spderosso

  Hi, I have an object A that has as an instance variable a collection of object Bs. Example: public class A{ String name; List<B> myList; ... public List<B> getMyList(){ return myList; } ... } I want this object to be the only source of information the jasper report gets, since all the information the report need is in A. I am currently doing something like: A myObjectA = new A(...); InputStream reportFile = MyPage.this.getClass().getResourceAsStream("test.jrxml"); HashMap<String, Object> parameters = new HashMap<String, Object>(); parameters.put("objectA", myObjectA); ... JasperReport report = JasperCompileManager.compileReport(reportFile); JasperPrint print = JasperFillManager.fillReport(report, parameters, new JRBeanCollectionDataSource(myObjectA.getMyList())); return JasperExportManager.exportReportToPdf(print); thereby passing "two" parameters, the objectA as a concrete parameter and the collection of object Bs that is in A as a bean data source. How do I iterate over the Bs in A by passing only A? Thanks!

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• Use interface between model and view in ASP.NET MVC

  - by Icerman

  Hi, I am using asp.net MVC 2 to develop a site. IUser is used to be the interface between model and view for better separation of concern. However, things turn to a little messy here. In the controller that handles user sign on: I have the following: IUserBll userBll = new UserBll(); IUser newUser = new User(); newUser.Username = answers[0].ToString(); newUser.Email = answers[1].ToString(); userBll.AddUser(newUser); The User class is defined in web project as a concrete class implementing IUser. There is a similar class in DAL implementing the same interface and used to persist data. However, when the userBll.AddUser is called, the newUser of type User can't be casted to the DAL User class even though both Users class implementing the interface (InvalidCastException). Using conversion operators maybe an option, but it will make the dependency between DAL and web which is against the initial goal of using interface. Any suggestions?

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• How to deserialize implementation classes in OSGi

  - by Daniel Schneller

  In an eRCP OSGi based application the user can push a button and go to a lock screen similar to that of Windows or Mac OS X. When this happens, the current state of the application is serialized to a file and control is handed over to the lock screen. In this mobile application memory is very tight, so we need to get rid of the original view/controller when the lock screen comes up. This works fine and we end up with a binary serialized file. Once the user logs back in, the file is read in again and the original state of the application restored. This works fine as well, except when the controller that was serialized contained a reference to an object which comes from a different bundle. In my concrete case the original controller (from bundle A) can call a web service and gets a result back. Nothing fancy, just some Strings and Numbers in a simple value holder class. However the controller only sees this as a Result interface; the actual runtime object (ResultImpl) is defined and created in a different bundle (bundle B, the webservice client implementation) and returned via a service call. When the deserialization now tries to thaw the controller from the file, it throws a ClassNotFound exception, complaining about not being able to deserialize the result object, because deserialization is called from bundle A, which cannot see the ResultImpl class from bundle B. Any ideas on how to work around that? The only thing I could come up with is to clone all the individual values into another object, defined in the controller's bundle, but this seems like quite a hassle.

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• how do use Ninject with class libraries I am developing?

  - by Greg

  Hi, If I am working on a class library how do I make use of Ninject here? Ie from the internal class library point of view and also from the client code? For example: should the class library have it's own IOC set up, or should it always assume the client code will supply? if no (ie it's upto the client to have the IOC in place) then where is the mapping data stored here'. Is this mapping of the class library's functionality to be places in the client? have a reusable library that is available, that uses interfaces with classes that use the getInstance concept to create concrete classes for you to use, then in this case would that make sense on the client side to use the IOC container to create instances of these classes? Or is that really applying a double layer of abstraction? Q2 Or in the cases where I'm building the reusable library myself and want the client to use an IOC container, then in my reusable library would I then dispense with any overhead of having factories or "getInstance" methods to instantiate the classes in the client? (i.e. as the IOC container would do this no?)

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• OOP, Interface Design and Encapsulation

  - by Mau

  C# project, but it could be applied to any OO languages. 3 interfaces interacting: public interface IPublicData {} public /* internal */ interface IInternalDataProducer { string GetData(); } public interface IPublicWorker { IPublicData DoWork(); IInternalDataProducer GetInternalProducer(); } public class Engine { Engine(IPublicWorker worker) {} IPublicData Run() { DoSomethingWith(worker.GetInternalProducer().GetData()); return worker.DoWork(); } } Clearly Engine is parametric in the actual worker that does the job. A further source of parametrization is how we produce the 'internal data' via IInternalDataProducer. This implementation requires IInternalDataProducer to be public because it's part of the declaration of the public interface IPublicWorker. However, I'd like it to be internal since it's only used by the engine. A solution is make the IPublicWorker produce the internal data itself, but that's not very elegant since there's only a couple of ways of producing it (while there are many more worker implementations), therefore it's nice to delegate to a couple of separate concrete classes. Moreover, the IInternalDataProducer is used in more places inside the engine, so it's good for the engine to pass around the actual object. I'm looking for elegant ideas/patterns. Cheers :-)

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• how does one _model_ data from relational databases in clojure ?

  - by sandeep

  I have asked this question on twitter as well the #clojure IRC channel, yet got no responses. There have been several articles about Clojure-for-Ruby-programmers, Clojure-for-lisp-programmers.. but what is the missing part is Clojure for ActiveRecord programmers . There have been articles about interacting with MongoDB, Redis, etc. - but these are key value stores at the end of the day. However, coming from a Rails background, we are used to thinking about databases in terms of inheritance - has_many, polymorphic, belongs_to, etc. The few articles about Clojure/Compojure + MySQL (ffclassic) - delve right into sql. Of course, it might be that an ORM induces impedence mismatch, but the fact remains that after thinking like ActiveRecord, it is very difficult to think any other way. I believe that relational DBs, lend themselves very well to the object-oriented paradigm because of them being , essentially, Sets. Stuff like activerecord is very well suited for modelling this data. For e.g. a blog - simply put class Post < ActiveRecord::Base has_many :comments end class Comment < ActiveRecord::Base belongs_to :post end How does one model this in Clojure - which is so strictly anti-OO ? Perhaps the question would have been better if it referred to all functional programming languages, but I am more interested from a Clojure standpoint (and Clojure examples)

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• Namespace constraint with generic class decleration

  - by SomeGuy

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

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• Circular dependency with generics

  - by devoured elysium

  I have defined the following interface: public interface IStateSpace<State, Action> where State : IState where Action : IAction<State, Action> // <-- this is the line that bothers me { void SetValueAt(State state, Action action); Action GetValueAt(State state); } Basically, an IStateSpace interface should be something like a chess board, and in each position of the chess board you have a set of possible movements to do. Those movements here are called IActions. I have defined this interface this way so I can accommodate for different implementations: I can then define concrete classes that implement 2D matrix, 3D matrix, graphs, etc. public interface IAction<State, Action> { IStateSpace<State, Action> StateSpace { get; } } An IAction, would be to move up(this is, if in (2, 2) move to (2, 1)), move down, etc. Now, I'll want that each action has access to a StateSpace so it can do some checking logic. Is this implementation correct? Or is this a bad case of a circular dependence? If yes, how to accomplish "the same" in a different way? Thanks

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• Find all CSS rules that apply to an element

  - by Carl Byström

  Many tools/APIs provide ways of selecting elements of specific classes or IDs. There's also possible to inspect the raw stylesheets loaded by the browser. However, for browsers to render an element, they'll compile all CSS rules (possibly from different stylesheet files) and apply it to the element. This is what you see with Firebug or the WebKit Inspector - the full CSS inheritance tree for an element. How can I reproduce this feature in pure JavaScript without requiring additional browser plugins? Perhaps an example can provide some clarification for what I'm looking for: <style type="text/css"> p { color :red; } #description { font-size: 20px; } </style> <p id="description">Lorem ipsum</p> Here the p#description element have two CSS rules applied: a red color and a font size of 20 px. I would like to find the source from where these computed CSS rules originate from (color comes the p rule and so on).

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• Vertically Merge Multiple Tables in MySQL by Joint Primary Key

  - by world

  Hello, I'll attempt to make my question as clear as possible. I'm fairly unexperienced with SQL, only know the really basic queries. In order to have a better idea I'd been reading the MySQL manual for the past few days, but I couldn't really find a concrete solution and my needs are quite specific. I've got 3 MySQL MyISAM tables: table1, table2 and table3. Each table has an ID column (ID, ID2, ID3 respectively), and different data columns. For example table1 has [ID, Name, Birthday, Status, ...] columns, table2 has [ID2, Country, Zip, ...], table3 has [ID3, Source, Phone, ...] you get the idea. The ID, ID2, ID3 columns are common to all three tables... if there's an ID value in table1 it will also appear in table2 and table3. The number of rows in these tables is identical, about 10m rows in each table. What I'd like to do is create a new table that contains (most of) the columns of all three tables and merge them into it. The dates, for instance, must be converted because right now they're in VARCHAR YYYYMMDD format. Reading the MySQL manual I figured STR_TO_DATE() would do the job, but I don't know how to write the query itself in the first place so I have no idea how to integrate the date conversion. So basically, after I create the new table (which I do know how to do), how can I merge the three tables into it, integrating into the query the date conversion?

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• c++-to-python swig caused memory leak! Related to Py_BuildValue and SWIG_NewPointerObj

  - by usfree74

  Hey gurus, I have the following Swig code that caused memory leak. PyObject* FindBestMatch(const Bar& fp) { Foo* ptr(new Foo()); float match; // call a function to fill the foo pointer return Py_BuildValue( "(fO)", match, SWIG_NewPointerObj(ptr, SWIGTYPE_p_Foo, 0 /* own */)); } I figured that ptr is not freed properly. So I did the following: PyObject* FindBestMatch(const Bar& fp) { Foo* ptr(new Foo()); float match; // call a function to fill the foo pointer *PyObject *o = SWIG_NewPointerObj(ptr, SWIGTYPE_p_Foo, 1 /* own */);* <------- 1 means pass the ownership to python PyObject *result = Py_BuildValue("(fO)", match, o); Py_XDECREF(o); return result; } But I am not very sure whether this will cause memory corruption. Here, Py_XDECREF(o) will decrease the ref count, which can free memory used by object "o". But o is part of the return value "result". Freeing "o" can cause data corrupt, I guess? I tried my change. It works fine and the caller (python code) does see the expected data. But this could be because nobody else overwrites to that memory area. So what's the right way to deal with memory management of the above code? I search the swig docs, but don't see very concrete description. Please help! Thanks, xin

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• How to create a platform ontop of CSLA? <-- if in case it make sense

  - by Peejay

  Hi all! here is the senario, i'm developing an application using csla 3.8 / c#.net, the application will have different modules. its like an ERP, it will have accounting, daily time record, recruitment etc as modules. Now the requirement is to check for common entities per module and build a "platform" (<- the boss calls it that way) from it. for example, DTR will have an entity "employee", Recruitment will have "Applicant" so one common entity that you can derive from both that can be put in the platform is "Person". "Person" will contain typical info like name, address, contact info etc. I know it sounds like OOP 101. the thing is, i dont know how i am to go about it. how i wish it was just a simple inheritance but the requirement is like to create an API of some sort to be used by the modules using CSLA. in csla you create smart objects right, inheriting from the base classes of csla like businessListbase, readonlylistbase etc. right? what if for example i created a businessbase Applicant class, it will have properties like salary demand, availability date etc. now for the personal info i will need the "Person" from the "platform" and implement it to the applicant class. so in summary i have several questions: how to create such platform? if such platform is possible, how will it be implemented on each module's entities? (im already inheriting from base clases of csla) if incase 1 and 2 are possible, does it have advantages on development and maintenace of the app? the reason why i'm asking #3 is because the way i see it, even if i am able to create a platform for that, i will be needing to define properties of the platform entity on my module entities so to have validation and all. im sorry if i'm typing nonesense i'm really confused. hope someone could enlighten me. thank you all!

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• Can't add to NSMutableArray from SecondaryView

  - by Antonio

  Hi guys, I've searched and read and still haven't found a concrete answer. Brief: I have an application where I declare an NSMutableArray in my AppDelegate to synthesize when the application loads. (code below). I have a SecondaryViewController call this function, and I have it output a string to let me know what the array size is. Every time I run it, it executes but it does not add any objects to the array. How do I fix this? AppDelegate.h file #import <UIKit/UIKit.h> @class arrayTestViewController; @interface arrayTestAppDelegate : NSObject <UIApplicationDelegate> { UIWindow *window; arrayTestViewController *viewController; NSMutableArray *myArray3; } @property (nonatomic, retain) NSMutableArray *myArray3; @property (nonatomic, retain) IBOutlet UIWindow *window; @property (nonatomic, retain) IBOutlet arrayTestViewController *viewController; -(void)addToArray3; @end AppDelegate.m file #import "arrayTestAppDelegate.h" #import "arrayTestViewController.h" @implementation arrayTestAppDelegate @synthesize window; @synthesize viewController; @synthesize myArray3; #pragma mark - #pragma mark Application lifecycle - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { myArray3 = [[NSMutableArray alloc] init]; // Override point for customization after application launch. // Add the view controller's view to the window and display. [window addSubview:viewController.view]; [window makeKeyAndVisible]; return YES; } -(void)addToArray3{ NSLog(@"Array Count: %d", [myArray3 count]); [myArray3 addObject:@"Test"]; NSLog(@"Array triggered from SecondViewController"); NSLog(@"Array Count: %d", [myArray3 count]); } SecondViewController.m file #import "SecondViewController.h" #import "arrayTestAppDelegate.h" @implementation SecondViewController -(IBAction)addToArray{ arrayTestAppDelegate *object = [[arrayTestAppDelegate alloc] init]; [object addToArray3]; }

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• What exactly is a reentrant function?

  - by eSKay

  Most of the times, the definition of reentrance is quoted from Wikipedia: A computer program or routine is described as reentrant if it can be safely called again before its previous invocation has been completed (i.e it can be safely executed concurrently). To be reentrant, a computer program or routine: Must hold no static (or global) non-constant data. Must not return the address to static (or global) non-constant data. Must work only on the data provided to it by the caller. Must not rely on locks to singleton resources. Must not modify its own code (unless executing in its own unique thread storage) Must not call non-reentrant computer programs or routines. How is safely defined? If a program can be safely executed concurrently, does it always mean that it is reentrant? What exactly is the common thread between the six points mentioned that I should keep in mind while checking my code for reentrant capabilities? Also, Are all recursive functions reentrant? Are all thread-safe functions reentrant? Are all recursive and thread-safe functions reentrant? While writing this question, one thing comes to mind: Are the terms like reentrance and thread safety absolute at all i.e. do they have fixed concrete definations? For, if they are not, this question is not very meaningful. Thanks!

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• c++ Design pattern for CoW, inherited classes, and variable shared data?

  - by krunk

  I've designed a copy-on-write base class. The class holds the default set of data needed by all children in a shared data model/CoW model. The derived classes also have data that only pertains to them, but should be CoW between other instances of that derived class. I'm looking for a clean way to implement this. If I had a base class FooInterface with shared data FooDataPrivate and a derived object FooDerived. I could create a FooDerivedDataPrivate. The underlying data structure would not effect the exposed getters/setters API, so it's not about how a user interfaces with the objects. I'm just wondering if this is a typical MO for such cases or if there's a better/cleaner way? What peeks my interest, is I see the potential of inheritance between the the private data classes. E.g. FooDerivedDataPrivate : public FooDataPrivate, but I'm not seeing a way to take advantage of that polymorphism in my derived classes. class FooDataPrivate { public: Ref ref; // atomic reference counting object int a; int b; int c; }; class FooInterface { public: // constructors and such // .... // methods are implemented to be copy on write. void setA(int val); void setB(int val); void setC(int val); // copy constructors, destructors, etc. all CoW friendly private: FooDataPrivate *data; }; class FooDerived : public FooInterface { public: FooDerived() : FooInterface() {} private: // need more shared data for FooDerived // this is the ???, how is this best done cleanly? };

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