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  • Override java methods without affecting parent behaviour

    - by Timmmm
    suppose I have this classes (sorry it's kind of hard to think of a simple example here; I don't want any "why would you want to do that?" answers!): class Squarer { public void setValue(int v) { mV = v; } public int getValue() { return mV; } private int mV; public void square() { setValue(getValue() * getValue()); } } class OnlyOddInputsSquarer extends Squarer { @Override public void setValue(int v) { if (v % 2 == 0) { print("Sorry, this class only lets you square odd numbers!") return; } super.setValue(v); } } auto s = new OnlyOddInputsSquarer(); s.setValue(3); s.square(); This won't work. When Squarer.square() calls setValue(), it will go to OnlyOddInputsSquarer.setValue() which will reject all its values (since all squares are even). Is there any way I can override setValue() so that all the functions in Squarer still use the method defined there? PS: Sorry, java doesn't have an auto keyword you haven't heard about! Wishful thinking on my part.

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  • Which is the correct design pattern for my PHP application?

    - by user1487141
    I've been struggling to find good way to implement my system which essentially matches the season and episode number of a show from a string, you can see the current working code here: https://github.com/huddy/tvfilename I'm currently rewriting this library and want a nicer way to implement how the the match happens, currently essentially the way it works is: There's a folder with classes in it (called handlers), every handler is a class that implements an interface to ensure a method called match(); exists, this match method uses the regex stored in a property of that handler class (of which there are many) to try and match a season and episode. The class loads all of these handlers by instantiating each one into a array stored in a property, when I want to try and match some strings the method iterates over these objects calling match(); and the first one that returns true is then returned in a result set with the season and episode it matched. I don't really like this way of doing it, it's kind of hacky to me, and I'm hoping a design pattern can help, my ultimate goal is to do this using best practices and I wondered which one I should use? The other problems that exist are: More than one handler could match a string, so they have to be in an order to prevent the more greedy ones matching first, not sure if this is solvable as some of the regex patterns have to be greedy, but possibly a score system, something that shows a percentage of how likely the match is correct, i'd have no idea how to actually implement this though. I'm not if instantiating all those handlers is a good way of doing it, speed is important, but using best practices and sticking to design patterns to create good, extensible and maintainable code is my ultimate priority. It's worth noting the handler classes sometimes do other things than just regex matching, they sometimes prep the string to be matched by removing common words etc. Cheers for any help Billy

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  • Javascript Instance Variable Syntax (AJAX page refresh)

    - by Rosarch
    I'm having difficulty with Javascript instance variables. I'm trying to make an easy way to refresh the chat page, looking for new messages. The AJAX call supplies a mid, or the lowest message id to be returned. This allows the call to only ask for the most recent messages, instead of all of them. MessageRefresher.prototype._latest_mid; function MessageRefresher(latest_mid) { this._latest_mid = latest_mid; // it thinks `this` refers to the MessageRefresher object } MessageRefresher.prototype.refresh = function () { refreshMessages(this._latest_mid); // it thinks `this` refers to the window this._latest_mid++; } function refreshMessages(latest_mid) { $.getJSON('API/read_messages', { room_id: $.getUrlVar('key'), mid: latest_mid }, function (messages) { for (var i = 0; i < messages[0].length; i++) { var newChild = sprintf("<li>%s: %s</li>", messages[1][i], messages[0][i]); $("#messages").append(newChild); } }); var messageRefresher = new MessageRefresher(0); setInterval(messageRefresher.refresh, 1000); This results in all the messages being printed out, over and over again. I know it has other bugs, but the main issue I'm trying to work out right now is the use of the instance variable. Or is there another way I should be going about doing this?

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  • Would this constructor be acceptable practice?

    - by Robb
    Let's assume I have a c++ class that have properly implemented a copy constructor and an overloaded = operator. By properly implemented I mean they are working and perform a deep copy: Class1::Class1(const Class1 &class1) { // Perform copy } Class1& Class1::operator=(const Class1 *class1) { // perform copy return *this; } Now lets say I have this constructor as well: Class1::Class1(Class1 *class1) { *this = *class1; } My question is would the above constructor be acceptable practice? This is code that i've inherited and maintaining.

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  • how to learn a library/framework structure?

    - by fayer
    a lot of people are contributing to open source libraries/frameworks. i wonder how these people learn the structure so that they can contribute? lets take doctrine and symfony as an example. is there a blueprint over these frameworks to give the developers an insight of the structure? or do they just download it and study the code? how does it work? please you contributors, share your learning strategies! thanks

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  • How to "wrap" implementation in C#

    - by igor
    Hello, I have these classes in C# (.NET Framework 3.5) described below: public class Base { public int State {get; set;} public virtual int Method1(){} public virtual string Method2(){} ... public virtual void Method10(){} } public class B: Base { // some implementation } public class Proxy: Base { private B _b; public class Proxy(B b) { _b = b; } public override int Method1() { if (State == Running) return _b.Method1(); else return base.Method1(); } public override string Method2() { if (State == Running) return _b.Method2(); else return base.Method2(); } public override void Method10() { if (State == Running) _b.Method10(); else base.Method10(); } } I want to get something this: public Base GetStateDependentImplementation() { if (State == Running) // may be some other rule return _b; else return base; // compile error } and my Proxy's implementation will be: public class Proxy: Base { ... public override int Method1() { return GetStateDependentImplementation().Method1(); } public override string Method2() { return GetStateDependentImplementation().Method2(); } ... } Of course, I can do this (aggregation of base implementation): public RepeaterOfBase: Base // no any overrides, just inheritance { } public class Proxy: Base { private B _b; private RepeaterOfBase _Base; public class Proxy(B b, RepeaterOfBase aBase) { _b = b; _base = aBase; } } ... public Base GetStateDependentImplementation() { if (State == Running) return _b; else return _Base; } ... But instance of Base class is very huge and I have to avoid to have other additional copy in memory. So I have to simplify my code have to "wrap" implementation have to avoid a code duplication have to avoid aggregation of any additional instance of Base class (duplication) Is it possible to reach these goals?

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  • frameworks for coding a php library?

    - by ajsie
    there are plenty of frameworks for coding MVC web applications. this time im going to code a library (think of Doctrine or Solr) with a bunch of class files. u just include a bootstrap or a class file and you are ready to use my classes. i have never tried to code a library before and intend to code one for learning purpose so that i can use various design patterns i have learned. are there any great frameworks for this, how i should organize the different class files, where i can put configuration files and so on? tutorials or other information would be great too. thanks

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  • How do you determine how coarse or fine-grained a 'responsibility' should be when using the single r

    - by Mark Rogers
    In the SRP, a 'responsibility' is usually described as 'a reason to change', so that each class (or object?) should have only one reason someone should have to go in there and change it. But if you take this to the extreme fine-grain you could say that an object adding two numbers together is a responsibility and a possible reason to change. Therefore the object should contain no other logic, because it would produce another reason for change. I'm curious if there is anyone out there that has any strategies for 'scoping', the single-responsibility principle that's slightly less objective?

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  • How can i split up a component using cfinclude and still use inheritance?

    - by rip747
    Note: this is just a simplized example of what i'm trying to do to get the idea across. The problem I'm having is that I want to use cfinclude inside cfcomponent so that i can group like methods into separate files for more manageability. The problem I'm running into is when i try to extend another component that also uses cfinclude to manage it's method as demostrated below. Note that ComponentA extends ComponentB: ComponentA ========== <cfcomponent output="false" extends="componentb"> <cfinclude template="componenta/methods.cfm"> </cfcomponent> componenta/methods.cfm ====================== <cffunction name="a"><cfreturn "componenta-a"></cffunction> <cffunction name="b"><cfreturn "componenta-b"></cffunction> <cffunction name="c"><cfreturn "componenta-c"></cffunction> <cffunction name="d"><cfreturn super.a()></cffunction> ComponentB ========== <cfcomponent output="false"> <cfinclude template="componentb/methods.cfm"> </cfcomponent> componentb/methods.cfm ====================== <cffunction name="a"><cfreturn "componentb-a"></cffunction> <cffunction name="b"><cfreturn "componentb-b"></cffunction> <cffunction name="c"><cfreturn "componentb-c"></cffunction> The issue is that when i try to initialize ComponentA I get an the error: "Routines cannot be declared more than once. The routine a has been declared twice in different templates." The whole reason for this is because when you use cfinclude it's evaluated at RUN TIME instead of COMPILE TIME. Short of moving the methods into the components themselves and eliminating the use of cfinclude, how can i get around this or does someone have a better idea splitting up large components?

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  • Session State Anti-Pattern

    - by Curiosity
    I know the SOLID principles and other design patterns fairly well and have been programming for some time now - seeing many a bit of code throughout the years. Having said that, I'm having trouble coming up with a name to give the pattern, or lack thereof, to bits of code I've been dealing with at a current engagement. The application is an ASP.NET C# WebForms application, backed by a SQL Server/Mainframe backend (more mainframe than backend) and it's riddled with Session State properties being accessed/mutated from multiple pages/classes. Accessing/mutating global variables/application state was usually shunned upon while I was in school. Apparently the creators of this magnificent application didn't think it was such a bad idea. Question: Is there a name for such a pattern/anti-pattern that relies so heavily on Session State? I'd like to call the pig by its name ...

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  • which situation abstract class i should use

    - by Bharanikumar
    Hi , Am not worked on extream level of oops in my projects , So i have little doubts , In which situation should i use abstract method or classes , Basically i know about abstract class definition and flow, I got details from this URL Doubt is which situation should i use abstract class and methods ,

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  • can I put my sqlite connection and cursor in a function?

    - by steini
    I was thinking I'd try to make my sqlite db connection a function instead of copy/pasting the ~6 lines needed to connect and execute a query all over the place. I'd like to make it versatile so I can use the same function for create/select/insert/etc... Below is what I have tried. The 'INSERT' and 'CREATE TABLE' queries are working, but if I do a 'SELECT' query, how can I work with the values it fetches outside of the function? Usually I'd like to print the values it fetches and also do other things with them. When I do it like below I get an error Traceback (most recent call last): File "C:\Users\steini\Desktop\py\database\test3.py", line 15, in <module> for row in connection('testdb45.db', "select * from users"): ProgrammingError: Cannot operate on a closed database. So I guess the connection needs to be open so I can get the values from the cursor, but I need to close it so the file isn't always locked. Here's my testing code: import sqlite3 def connection (db, arg): conn = sqlite3.connect(db) conn.execute('pragma foreign_keys = on') cur = conn.cursor() cur.execute(arg) conn.commit() conn.close() return cur connection('testdb.db', "create table users ('user', 'email')") connection('testdb.db', "insert into users ('user', 'email') values ('joey', 'foo@bar')") for row in connection('testdb45.db', "select * from users"): print row How can I make this work?

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  • Best way to track the stages of a form across different controllers - $_GET or routing

    - by chrisj
    Hi, I am in a bit of a dilemma about how best to handle the following situation. I have a long registration process on a site, where there are around 10 form sections to fill in. Some of these forms relate specifically to the user and their own personal data, while most of them relate to the user's pets - my current set up handles user specific forms in a User_Controller (e.g via methods like user/profile, user/household etc), and similarly the pet related forms are handled in a Pet_Controller (e.g pet/health). Whether or not all of these methods should be combined into a single Registration_Controller, I'm not sure - I'm open to any advice on that. Anyway, my main issue is that I want to generate a progress bar which shows how far along in the registration process each user is. As the urls in each form section can potentially be mapping to different controllers, I'm trying to find a clean way to extract which stage a person is at in the overall process. I could just use the query string to pass a stage parameter with each request, e.g user/profile?stage=1. Another way to do it potentially is to use routing - e.g the urls for each section of the form could be set up to be registration/stage/1, registration/stage/2 - then i could just map these urls to the appropriate controller/method behind the scenes. If this makes any sense at all, does anyone have any advice for me?

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  • When do you use metaclasses?

    - by johannix
    Just started looking into metaclasses and while they seem powerful, I can think of other ways to accomplish the same type of thing. I was wondering when metaclasses have been found to be the right answer and why.

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  • Is it OK to write a constructor which does nothing?

    - by Roman
    To use methods of a class I need to instantiate a class. At the moment the class has not constructor (so I want to write it). But than I have realized that the constructor should do nothing (I do need to specify values of fields). In this context I have a question if it is OK to write constructor which does nothing. For example: public Point() { }

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  • How should I organize my C# classes? [closed]

    - by oscar.fimbres
    I'm creating an email generator system. I'm creating some clases and I'm trying to make things right. By the time, I have created 5 classes. Look at the class diagram: I'm going to explain you each one. Person. It's not a big deal. Just have two constructors: Person(fname, lname1, lname2) and Person(token, fname, lname1, lname2). Note that email property stays without value. StringGenerator. This is a static class and it has only a public function: Generate. The function receives a Person class and it will return a list of patterns for the email. MySql. It contains all the necessary to connect to a database. Database. This class inherits from MySql class. It has particular functions for the database. This gets all the registries from a table (function GetPeople) and return a List. Each person from the list contains all data except Email. Also it can add records (List but this must contains an available email). An available email is when an email doesn't have another person. For that reason, I have a method named ExistsEmail. Container. This is the class which is causing me some problems. It's like a temporary container. It supposed to have a people list from GetPeople (in Database class) and for each person it adds, it must generate a list of possible names (StringGenerator.Generate), then it selects one of the list and it must check out if exists in the database or in the same container. As I told above this is temporal, it may none of the possible emails is available. So the user can modify or enter a custom email available and update the list in this container. When all the email's people are available, it sends a list to add in the database, It must have a Flush method, to insert all the people in the database. I'm trying to design correct class. I need a little help to improve or edite the classes, because I want to separate the logic and visual, and learn of you. I hope you've been able to understand me. Any question or doubt, please let me know. Anyway, I attached the solution here to better understand it: http://www.megaupload.com/?d=D94FH8GZ

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  • OO C++ - Virtual Methods

    - by Phorce
    Just a really quick question here. I'm using virtual functions to read in from a text file. Now, it's virtual because in one aspect I want the values to be normalised, and, in the other respect I don't want them to be normalised. I have tried to do this: bool readwav(string theFile, 'native'); So in theory, if the 'native' is used, this method should be called, however, if 'double' is called then a different version of the method is called. Same for if the value is empty, it should just perform the native option. First question, why doesn't the declaration above work? Also, is this the best route to go down? Or, would it be better to have just one class method that switches between the options. Thanks :)

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  • How do I organize C# classes that inherit from one another, but also have properties that inherit from one another?

    - by Chris
    I have an application that has a concept of a Venue, a place where events happen. A Venue is owned by a Company and has many VenueParts. So, it looks like this: public abstract class Venue { public int Id { get; set; } public string Name { get; set; } public virtual Company Company { get; set; } public virtual ICollection<VenuePart> VenueParts { get; set; } } A Venue can be a GolfCourseVenue, which is a Venue that has a Slope and a specific kind of VenuePart called a HoleVenuePart: public class GolfCourseVenue { public string Slope { get; set; } public virtual ICollection<HoleVenuePart> Holes { get; set; } } In the future, there may also be other kinds of Venues that all inherit from Venue. They might add their own fields, and will always have VenueParts of their own specific type. My declarations above seem wrong, because now I have a GolfCourseVenue with two collections, when really it should just have the one. I can't override it, because the type is different, right? When I run reports, I would like to refer to the classes generically, where I just spit out Venues and VenueParts. But, when I render forms and such, I would like to be specific. I have a lot of relationships like this and am wondering what I am doing wrong. For example, I have an Order that has OrderItems, but also specific kinds of Orders that have specific kinds of OrderItems.

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  • Graphic editor opensource project example on c++ underlying composite pattern

    - by G-71
    Can you tell me when I can see a some opensource project (only project on C++ language), which is simple graphic editor, ?ontaining following primitive (for example): an ellipse, a rectangle, a line. And desirable, that to be able to group this primitive in one primitive (for example, Word Grouping - Group). Composite pattern use is desirable in this project. I want to see how to organize classes, but more serious for me is to see how organize grouping operation. I searched for it on codeproject.com codeproject.com, codeplex.com, but not found this. I have already some source http://pastebin.com/xe4JF5PW But in my opinion, this code is dirty and ugly. Therefore, I want to see some opensource project for example. Thanks!

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