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  • Explain "Leader/Follower" Pattern

    - by Alex B
    I can't seem to find a good explanation of "Leader/Follower" pattern. All explanations either simply refer to it in the context of some problem, or are completely meaningless. Can anyone explain to the the mechanics of how this pattern works, and why and how it improves performance over more traditional asynchronous IO models? Examples and links to diagrams are appreciated too.

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  • Saving an IP adddress to DB

    - by Mark
    I want to save a user's IP address to my database just in case any legal issues come up and we need to track down who performed what action. Since I highly doubt I will ever actually need to use this data (well, maybe for counting unique hits or something) do you think I can just dump the REMOTE_ADDR into a field? If so, what should the length of that field be? 39 chars should fit an IPv6 address, no? I don't know if I'll ever get any of those, but just in case...

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  • How do i free objects in C#

    - by assassin
    Hi, Can anyone please tell me how I can free objects in C#? For example, I have an object: Object obj1 = new Object(); //Some code using obj1 //Here I would like to free obj1, after it is no longer required and also more importantly its scope is the full run time of the program. Thanks for all your help

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  • Make a Method of the Business Layer secure. best practice / best pattern

    - by gsharp
    We are using ASP.NET with a lot of AJAX "Page Method" calls. The WebServices defined in the Page invokes methods from our BusinessLayer. To prevent hackers to call the Page Methods, we want to implement some security in the BusinessLayer. We are struggling with two different issues. First one: public List<Employees> GetAllEmployees() { // do stuff } This Method should be called by Authorized Users with the Role "HR". Second one: public Order GetMyOrder(int orderId) { // do sutff } This Method should only be called by the owner of the Order. I know it's easy to implement the security for each method like: public List<Employees> GetAllEmployees() { // check if the user is in Role HR } or public Order GetMyOrder(int orderId) { // check if the order.Owner = user } What I'm looking for is some pattern/best practice to implement this kind of security in a generic way (without coding the the if then else every time) I hope you get what i mean :-)

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  • How to bring the parent element with floated child elements to the center of the document?

    - by Starx
    I have organized a menu. Its HTML is as follows: <ul class="topmenu"> <li><a href="sample.html">Text 1</a></li> <li><a href="sample.html">Text 2</a></li> <li><a href="sample.html">Text 3</a></li> <li><a href="sample.html">Text 4</a></li> <ul> This is a horizontal menu, so I have floated the list items to left to appear them in a horizontal line. I could have used display:inline to appear them in a single line, but since IE does not support it and I don't know any other way to do so, I used float:left;. It's css is: .topmenu { list-style:none; margin:0; padding:0; } .topmenu li { float:left; } This brings the menu in a perfect horizontal line, but the entire list is floated to the left. I want to bring the .topmenu to appear in the center of the document and keep the listitem inside it floated towards the left. I found that this is achievable by defining width property of the .topmenu, but I dont want to fix its width as the list-items are dynamically generated and thus could increase and decrease. Any one know of any solution?

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  • Does introducing foreign keys to MySQL reduce performance

    - by Tam
    I'm building Ruby on Rails 2.3.5 app. By default, Ruby on Rails doesn't provide foreign key contraints so I have to do it manually. I was wondering if introducing foreign keys reduces query performance on the database side enough to make it not worth doing. Performance in this case is my first priority as I can check for data consistency with code. What is your recommendation in general? do you recommend using foreign keys? and how do you suggest I should measure this?

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  • Make Java parent class not part of the interface

    - by Bart van Heukelom
    (This is a hypothetical question for discussion, I have no actual problem). Say that I'm making an implementation of SortedSet by extending LinkedHashMap: class LinkedHashSortedMapThing extends LinkedHashMap implements SortedSet { ... } Now programmers who use this class may do LinkedHashMap x = new LinkedHashSortedMapThing(); But what if I consider the extending of LinkedHashMap an implementation detail, and do not want it to be a part of the class' contract? If people use the line above, I can no longer freely change this detail without worrying about breaking existing code. Is there any way to prevent this sort of thing, other than favouring composition over inheritance (which is not always possible due to private/protected members)?

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  • Conceptually, how does replay work in a game?

    - by SnOrfus
    I was kind of curious as to how replay might be implemented in a game. Initially, I thought that there would be just a command list of every player/ai action that was taken in the game, and it then 're-plays' the game and lets the engine render as usual. However, I have looked at replays in FPS/RTS games, and upon careful inspection even things like the particles and graphical/audible glitches are consistent (and those glitches are generally *in*consistent). So How does this happen. In fixed camera angle games I though it might just write every frame of the whole scene to a stream that gets stored and then just replays the stream back, but that doesn't seem like enough for games that allow you to pause and move the camera around. You'd have to store the locations of everything in the scene at all points in time (No?). So for things like particles, that's a lot of data to push which seems like a significant draw on the game's performance whilst playing.

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  • PHP Object Oriented Web Application

    - by Sev
    I have a class called "Layout" for the layout of the page, another class called "User" for the user. Every page I create, I instantiate a new Layout. When a user logs in, there is a new User instantiated. How do I get an instance of the layout class to know about the instantiated user? I could also save the entire instance of the User in a session variable. I assume that's a bad idea though. What are the best practices for this?

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  • What's the most common scenario for Cocoa app setup during first launch?

    - by Eimantas
    I am creating an app and I would like a user to set some obligatory preferences during first app launch. What is the most common scenario to achieve this? Should I set some user defaults to see if the app has been setup? Also - if I determine that the app is being launched for the first time - how should I display "Setup" window? If I load it from the separte xib file - how will I deffer the display of main app window?

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  • Make a Method of the Business Layer secure. best practice / best pattern [.net/c#]

    - by gsharp
    Hi We are using ASP.NET with a lot of AJAX "Page Method" calls. The WebServices defined in the Page invokes methods from our BusinessLayer. To prevent hackers to call the Page Methods, we want to implement some security in the BusinessLayer. We are struggling with two different issues. First one: public List<Employees> GetAllEmployees() { // do stuff } This Method should be called by Authorized Users with the Role "HR". Second one: public Order GetMyOrder(int orderId) { // do sutff } This Method should only be called by the owner of the Order. I know it's easy to implement the security for each method like: public List<Employees> GetAllEmployees() { // check if the user is in Role HR } or public Order GetMyOrder(int orderId) { // check if the order.Owner = user } What I'm looking for is some pattern/best practice to implement this kind of security in a generic way (without coding the the if then else every time) I hope you get what i mean :-) Thanks for you help.

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  • Tree-like queues

    - by Rehno Lindeque
    I'm implementing a interpreter-like project for which I need a strange little scheduling queue. Since I'd like to try and avoid wheel-reinvention I was hoping someone could give me references to a similar structure or existing work. I know I can simply instantiate multiple queues as I go along, I'm just looking for some perspective by other people who might have better ideas than me ;) I envision that it might work something like this: The structure is a tree with a single root. You get a kind of "insert_iterator" to the root and then push elements onto it (e.g. a and b in the example below). However, at any point you can also split the iterator into multiple iterators, effectively creating branches. The branches cannot merge into a single queue again, but you can start popping elements from the front of the queue (again, using a kind of "visitor_iterator") until empty branches can be discarded (at your discretion). x -> y -> z a -> b -> { g -> h -> i -> j } f -> b Any ideas? Seems like a relatively simple structure to implement myself using a pool of circular buffers but I'm following the "think first, code later" strategy :) Thanks

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  • Script to sell php script?

    - by DR.GEWA
    Hi ppl. I am to finish my social network web-script which should be sold license based. I wonder such thing. There is a lot of shopping carts there. Is there a one, which is specialized on selling scripts and supportings them? Or should I part by part put a forum, make an order system, wiki, and so on?

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  • SQL Server (2008) Creating link tables with unique rows

    - by peteski22
    Hi guys, I'm having trouble getting in touch with SQL Server Managemen Studio 2008! I want to create a link-table that will link an Event to many Audiences (EventAudience). An example of the data that could be contained: EventId | AudienceId 4 1 5 1 4 2 However, I don't want this: EventId | AudienceId 4 1 4 1 I've been looking at relationships and constraints.. but no joy so far! As a sneaky second part to the question, I would like to set up the Audience table such that if a row is deleted from Audience, it will clear down the EventAudience link table in a cascading manner. As always, ANY help/advice appreciated! Thanks Pete

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  • Looking for Programming Language that allows you to change true and false.

    - by Maushu
    For my curiosity sake I'm looking for a dynamic object oriented language that allows you to change true to false and vice versa. Something like this: true = false, false = true; This should also affect any conditional statements, therefore 42 == 42 should return False. Basically, with this premise, nothing in the language would be safe from the programmer. Is there any language like this?

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  • App store for the PC?

    - by Chris
    So I've spent a lot of time making an iPhone game and have recently realized that I don't have to limit myself to just Apple - I know there are app stores for Palm and Android, but does anybody know of a good "app store" for the plain old PC? I would like to have one where individual developers can publish an app and not have to worry about all the billing and piracy issues!

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  • Can I change class types in a setter with an object-oriented language?

    - by user214626
    Hello, Here is the problem statement : Calling a setter on the object should result in the object to change to an object of a different class, which language can support this ? Ex. I have a class called "Man" (Parent Class), and two children namely "Toddler" and "Old Man", they are its children because they override a behaviour in Man called as walk.( i.e Toddler sometimes walks using both his hands and legs kneeled down and the Old man uses a stick to support himself). The Man class has a attribute called age, I have a setter on Man,say it is called setAge(int ageValue). I have 3 objects, 2 toddlers, 1 old-Man. (The system is up and running,i guess when we say objects it is obvious) .I will make this call, toddler.setAge(80), I expect the toddler to change to an object of type Old Man. Is this possible.Please suggest. Thanks,

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  • Open closed prinicple, problem

    - by Marcus
    Hi, I'm trying to apply OCP to a code snippet I have that in it's current state is really smelly, but I feel I'm not getting all the way to the end. Current code: public abstract class SomeObject {} public class SpecificObject1 : SomeObject {} public class SpecificObject2 : SomeObject {} // Smelly code public class Model { public void Store(SomeObject someObject) { if (someObject is SpecificObject1) {} else if (someObject is SpecificObject2) {} } } That is really ugly, my new approach looks like this: // No so smelly code public class Model { public void Store(SomeObject someObject) { throw new Expception("Not allowed!"); } public void Store(SpecificObject1 someObject) {} public void Store(SpecificObject2 someObject) {} } When a new SomeObject type comes along I must implement how that specific object is stored, this will break OCP cause I need to alter the Model-class. To move the store logic to SomeObject also feels wrong cause then I will violate SRP (?), becuase in this case the SomeObject is almost like a DTO, it's resposibility it not how to know to store itself. If a new implementation to SomeObject comes along who's store implementation is missing I will get a runtime error due to exception in Store method in Model class, it also feels like a code smell. This is because calling code will in the form of IEnumerable<SomeObject> sequence; I will not know the specific types of the sequence objects. I can't seem to grasp the OCP-concept. Anyone has any concrete examples or links that is a bit more than just some Car/Fruit example?

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