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  • what pattern to use for multi-argument method?

    - by Omid S
    I have a method with the following signature: foo (Sample sample, Aliquot aliquot) "foo" needs to alter a Sample object, either the first argument or from the second argument it can extract its Sample. For example: foo (Sample sample, Aliquot aliquot) { Sample out = null; if (sample != null) out = sample else out = aliquot.getSample() return out; } But that is so un-elegant, other than reading the API a developer does not know the reference of the first argument overrides the Sample of the second argument. Now, I could change "foo" to foo (SomeMagicalObject bar) where SomeMagicalObject is a tuple for Sample and Aliquot and holds some logic ... etc. But I am wondering, are there some patterns for this question?

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  • Php PEAR, Database Abstraction & Factory Methods

    - by pws5068
    I'm interested in learning more about design practices in PHP for Database Abstraction & Factory methods. For background, my site is a special-interest social networking community currently in beta mode. Currently, I've started moving my old code for object retrieval to factory methods. However, I do feel like I'm limiting myself by keeping a lot of SQL table names and structure separated in each function/method. Questions: 1.) Is there a reason to use PEAR (or similar) if I dont anticipate switching databases? 2.) Can PEAR interface with the MySqli prepared statements I currently use? 3.) Will it help me separate table names from each method? (If no, what other design patterns might I want to research?) 4.) Will it slow down my site once I have a significantly large member base?

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  • Which design pattern should I be using?

    - by Gabriel
    Here's briefly what I'm trying to do. The user supplies me with a link to a photo from one of several photo-sharing websites (such as Flickr, Zooomr, et. al). I then do some processing on the photo using their respective APIs. Right now, I'm only implementing one service, but I will most likely add more in the near future. I don't want to have a bunch of if/else or switch statements to define the logic for the different websites (but maybe that's necessary?) I'd rather just call GetImage(url) and have it get me the image from whatever service the url's domain is from. I'm confused how the GetImage function and classes should be designed. Maybe I need the strategy pattern? I'm still reading and trying to understand the various design patterns and how I could make one fit in this case. I'm doing this in C#, but this question is language-agnostic.

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  • abstract method signature, inheritance, and "Do" naming convention

    - by T. Webster
    I'm learning about design patterns and in examples of code I've seen a convention where the abstract class declares a method, for example: public abstract class ServiceBase { ... public virtual object GetSomething(); and then protected abstract object DoGetSomething(); My question is on why these two methods exist, since they appear to serve the same purpose. Is this so that the base class GetSomething() method logic cannot be overridden by inherited classes? But then again, the method is marked virtual, so it can be overridden anyway. What is the usefulness here in requiring derived class implementers to implement the abstract method when the virtual method can be called anyway?

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  • What is the difference between MVC model 1 and model 2?

    - by Alex Ciminian
    I've recently discovered that MVC is supposed to have two different flavors, model one and model two. I'm supposed to give a presentation on MVC1 and I was instructed that "it's not the web based version, that is refered to as MVC2". As the presentations are about design patterns in general, I doubt that this separation is related to Java (I found some info on Sun's site, but it seemed far off) or ASP. I have a pretty good understanding of what MVC is and I've used several (web) frameworks that enforce it, but this terminology is new to me. How is the web-based version different from other MVC (I'm guessing GUI) implementations? Does it have something to do with the stateless nature of HTTP? Thanks, Alex

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  • Typical tasks/problems to demonstrate differences between programming languages

    - by Space_C0wb0y
    Somewhere some guy said (I honestly do not know where I got this from), that one should learn one programming language per year. I can see where that might be a good idea, because you learn new patterns and ways to look at the same problems by solving them in different languages. Typically, when learning a new language, I look at how certain problems are supposed to be solved in that language. My question now is, what, in you experience, are good, simple, and clearly defined tasks that demostrate the differences between programming languages. The Idea here is to have a set of tasks, that, when I solve all of them in the language I am learning, gives me a good overview of how things are supposed to be done in that language. I do not know if that is even possible, but it sure would be a useful thing to have. A typical example one often sees especially in tutorials for functional languages is the implementation of quicksort.

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  • Database Abstraction & Factory Methods

    - by pws5068
    I'm interested in learning more about design practices in PHP for Database Abstraction & Factory methods. For background, my site is a common-interest social networking community currently in beta mode. Currently, I've started moving my old code for object retrieval to factory methods. However, I do feel like I'm limiting myself by keeping a lot of SQL table names and structure separated in each function/method. Questions: Is there a reason to use PEAR (or similar) if I dont anticipate switching databases? Can PEAR interface with the MySqli prepared statements I currently use? Will it help me separate table names from each method? (If no, what other design patterns might I want to research?) Will it slow down my site once I have a significantly large member base?

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  • Is it possible, with simple F# pattern matching transformations, to ignore unmatched values without

    - by Phobis
    So, I previously asked this question: http://stackoverflow.com/questions/2820234/can-someone-help-me-compare-using-f-over-c-in-this-specific-example-ip-address I was looking at the posted code and I was wondering if this code could be written without it producing a warning: let [|a;b;c;d|] = s.Split [|'.'|] IP(parseOrParts a, parseOrParts b, parseOrParts c, parseOrParts d) Is it possible to do something for the match _ pattern ot ignore? Without adding in something like Active Patterns? i want to keep the code as simple as possible... can I do this without drastically changing this code? NOTE: Warning is as follows Warning Incomplete pattern matches on this expression. For example, the value '[|_; _; _; _; _|]' may indicate a case not covered by the pattern(s).

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  • Decorator Pattern - Multiple wrappers or quantity property?

    - by Jiminizer
    I'm making use of the decorator pattern for one of the first times, as part of a Uni project. As far as I can see, the pattern seems to be meant more for adding functionality in a modular manner, however we've been taught it with uses such as a coffee or pizza maker, where the object has modular components that are added - changing properties rather than behaviour. I'm trying to make the most of both uses, however I've come up with a question. In the example in the book we're using (Head First Design Patterns), the pattern is used in a coffee shop creating different coffees. So, for example, milk, froth, sugar, sprinkles are all decorators. How would you implement a system that used the same decorator multiple times (for example, a coffee with two sugars)? Would you rewrap the coffee, or give sugar a quantity property? Or (as i'm starting to suspect) would this never be an issue as the pattern isn't designed to be used this way?

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  • ready to use design pattern APIs for PHP?

    - by ajsie
    i know that in Java you can use their built-in APIs for design pattern. eg. if you want to use the observer pattern, you just have to extend your Subject class with the Observable class. is this possible for PHP? are there any libraries for the design patterns ready to use. in this way you don't have to reinvent the wheel and you also let many developers follow a standard. does Zend library have these API:s?

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  • Question regarding two dimensional array

    - by Sherwood Hu
    I have some problems using two dimensional array in the code and need some help. static const int PATTERNS[20][4]; static void init_PATTERN() { // problem #1 int (&patterns)[20][4] = const_cast<int[20][4]>(PATTERNS); ... } extern void UsePattern(int a, const int** patterns, int patterns_size); // problem #2 UsePattern(10, PATTERNS, sizeof(PATTERNS)/sizeof(PATTERNS[0])); in the first statement, I need to cast the const off the two dimensional array PATTERNS. The reason for this is that the init function is called only once, and in the remaining code, PATTERNS is strictly read-only. In the second statement, I need to pass PATTERNS array to the int** argument. Direct passing resulted a compile error. Thanks!

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  • How to solve the "Growing If Statement" problem?

    - by Achilles
    I've been doing some reading about design patterns and wanted some perspective. Consider the following: Dim objGruntWorker as IGruntWorker if SomeCriteria then objGruntWorker = new GoFor() else if SomeOtherCriteria then objGruntWorker = new Newb() else if SomeCriteriaAndTheKitchenSink then objGruntWorker = new CubeRat() end if objGruntWorker.GetBreakfast() system.threading.thread.sleep(GetMilliSecondsFromHours(4)) objGruntWorker.GetLunch() The above code grows each time a new Criteria arises. I've seen code like this all over the place and in ignorance wrote some of it myself. How should this be solved? Does this kind of anti-pattern have a more "formal" name? Thanks for your help!

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  • How big teams work with database

    - by Michael Riva
    Lets say I have a team, 20 developers. And we are making a project on .net. In team every one can easy create their tables according to their modules working on it. And we think to use an ORM, can you tell me how can and which ORM tools for good to working with team. Is there any proven way? I m asking becouse I never work with a team, so I dont know the best practices. So you guys what kind of pattern you use?. I realy wonder. The team members can write their unit tests and supply necessary design patterns. What kind of approach I need to create to manage team? What kind of ORM tools that we have to use?

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  • Design pattern to encapsulate common funtionality among UI controls

    - by Dan
    I'm brainstorming some ideas around a pattern to use for the following scenario. I have some 3rd party controls that I want to add common functionality to. Functionality is added by handling several of the the events and doing certain things when the events fire along with adding some private variables to hold some state info between events. I want to reuse the code and functionality so this is what I'd typically do. Create a class for this functionality and pass in the instance of the control that I want to add the functionality to in the constructor. Then I can add event handlers to the control in the instance of the class. Can anyone think of alternative patterns to use in order to create this kind of reusable functionality.

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  • Where can I learn advanced Haskell?

    - by FredOverflow
    In a comment to one of my answers, SO user sdcwc essentially pointed out that the following code: comb 0 = [[]] comb n = let rest = comb (n-1) in map ('0':) rest ++ map ('1':) rest could be replaced by: comb n = replicateM n "01" which had me completely stunned. Now I am looking for a tutorial, book or PDF that teaches these advanced concepts. I am not looking for a "what's a monad" tutorial aimed at beginners or online references explaining the type of replicateM. I want to learn how to think in monads and use them effectively, monadic "patterns" if you will.

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  • High level programming logic, design, pattern

    - by Muhammad Shahzad
    I have been doing programming from last 7 years, getting better and better, but still i think that am lacking something. I have been doing work in JOOMLA, MAGENTO, WP, Custom PHP, Opencart, laravel, codeignitor. Sometimes i need to design logic for a huge database application, in the applications we need nesting loops and queries, although i follow OOPS standards, ORM etc, still i feel i need more robust coding designs. I need to know how can i improve these things, so that code remain neat, efficient and faster. Also how big webapps like facebook twitter tests there code speed? How high level programmers choose design patterns. If you can help me find something useful with examples?

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  • What lessons have you learned about using a wiki as a development tool?

    - by Vivek Kodira
    I'd asked a question a while back about ways to encourage my team to collaborate. The tool we use is a wiki. Since this is the first time we are using the wiki (formally and as a team), we are learning by committing mistakes. One of the lessons has been that a wiki isn't suitable for tracking activities. It is better to use a tool built for-the-job (will elaborate if necessary). Are there other such anti-patterns? What development tasks would you NOT recommend using a wiki for (even though it may seem suitable at first glance)? Edit: Making this a community-wiki since it is probably unlikely that there will be 'one' right answer.

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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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  • How to program a connection pool?

    - by the_drow
    Is there a known algorithm for implementing a connection pool? If not what are the known algorithms and what are their trade-offs? What design patterns are common when designing and programming a connection pool? Are there any code examples implement a connection pool using boost.asio? Is it a good idea to use a connection pool for presisting connections (not http)? How is threading related to connection pooling? When do you need a new thread?

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  • I have to generate PL/SQL using Java. Most of the procedures are common. Only a few keeps changing.

    - by blog
    I have to generate PL-SQL code, with some common code(invariable) and a variable code. I don't want to use any external tools. Some ways that I can think: Can I go and maintain the common code in a template and with markers, where my java code will generate code in the markers and generate a new file. Maintain the common code in static constant String and then generate the whole code in StringBuffer and at last write to file. But, I am not at all satisfied with both the ideas. Can you please suggest any better ways of doing this or the use of any design patterns or anything? Thanks in Advance.

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  • Design pattern for data entry forms with LINQ2SQL

    - by petebob796
    I am about to start a new winforms data entry application, it already has the database designed which I am comfortable with. I was going to use LINQ2SQL to access the tables to keep things type safe but am now wondering about design patterns, something I am just getting into. Since LINQ is giving me objects to use should I still create classes in between to hold the validation code and helper methods or should these just go in with the UI? It just seems I will end up with classes sat in between with little code which will cause the UI classes to have code just getting and setting values in the intermediate class and returning from validation to flag errors... Any good reading on this? Should I consider the entity framework (or similar) instead?

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  • Scala's tuple unwrapping nuance

    - by Paul Milovanov
    I've noticed the following behavior in scala when trying to unwrap tuples into vals: scala> val (A, B, C) = (1, 2, 3) <console>:5: error: not found: value A val (A, B, C) = (1, 2, 3) ^ <console>:5: error: not found: value B val (A, B, C) = (1, 2, 3) ^ <console>:5: error: not found: value C val (A, B, C) = (1, 2, 3) ^ scala> val (u, v, w) = (1, 2, 3) u: Int = 1 v: Int = 2 w: Int = 3 Is that because scala's pattern matching mechanism automatically presumes that all identifiers starting with capitals within patterns are constants, or is that due to some other reason? Thanks!

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  • Why and How to avoid Event Handler memory leaks ?

    - by gillyb
    Hey There, I just came to realize, by reading some questions and answers on StackOverflow, that adding event handlers using += in C# (or i guess, other .net languages) can cause common memory leaks... I have used event handlers like this in the past many times, and never realized that they can cause, or have caused, memory leaks in my applications. How does this work (meaning, why does this actually cause a memory leak) ? How can I fix this problem ? Is using -= to the same event handler enough ? Are there common design patterns or best practices for handling situations like this ? Example : How am I supposed to handle an application that has many different threads, using many different event handlers to raise several events on the UI ? Are there any good and simple ways to monitor this efficiently in an already built big application ? Thanks in advance!

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  • Writing Great Software

    - by 01010011
    Hi, I'm currently reading Head First's Object Oriented Analysis and Design. The book states that to write great software (i.e. software that is well-designed, well-coded, easy to maintain, reuse, and extend) you need to do three things: Firstly, make sure the software does everything the customer wants it to do Once step 1 is completed, apply Object Oriented principles and techniques to eliminate any duplicate code that might have slipped in Once steps 1 and 2 are complete, then apply design patterns to make sure the software is maintainable and reusable for years to come. My question is, do you follow these steps when developing great software? If not, what steps do you usually follow inorder to ensure it's well designed, well-coded, easy to maintain, reuse and extend?

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  • Does this pattern have a name?

    - by LK7jb
    Disclaimer: I'm trying to learn proper OO programming/design, so I'm pretty new to this stuff. I guess this is a general design patterns question, but I'll base my example on a game engine or something that renders objects to the display. Consider the following: How can this sort of separation between physical objects (e.g., cubes, spheres, etc.) and the rendering mechanism be achieved in an extensible manner? This design is not set in stone, and perhaps I've got something wrong from the start. I'm just curious as to how a problem like this is solved in real world code.

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