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  • is this a design pattern?

    - by Michel
    Hi all, i have to build some financial data report, and for making the calculation, there are a lot of 'if then' situations: if it's a large client, subtract 10%, if it's postal code equals '10101', add 10%, if the day is on a saturday, make a difficult calculation etc. so i once read about this kind of example, and what they did was (hope i remember well) create a class with some base info and make it possible to add all kinds of calculationobjects to it. So to put what i remembered in pseudo code Basecalc bc = new baseCalc(); //put the info in the bc so other objects can do their if bc.Add(new Largecustomercalc()); bc.Add(new PostalcodeCalc()); bc.add(new WeekdayCalc()); the the bc would run the Calc() methods of all of the added Calc objects. As i type this i think all the Calc objects must be able to see the Basecalc properties to correctly perform their calculation logic. So all the if's are in the different Calc objects and not ALL in the Basecalc. does this make sense? I was wondering if this is some kind of design pattern?

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  • What is MVC and what are the advantages of it?

    - by Teifion
    I found What are mvp and mvc and what is the difference but it didn't really answer this question. I've recently started using MVC because it's part of the framework that myself and my work-partner are going to use. We chose it because it looked easy and separated process from display, are there advantages besides this that we don't know about and could be missing out on? Pros Display and Processing are seperated Cons None so far

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  • Continuous integration with multiple branch development

    - by ryanprayogo
    In the project that I'm working on, we are using SVN with 'Stable Trunk' strategy. What that means is that for each bug that is found, QA opens a bug ticket and assigns it to a developer. Then, a developer fixes that bug and checks it in a branch (off trunk, let's call this the bug branch) and that branch will only contain fixes for that particular bug ticket When we decided to do a release, for each bug fixes that we want to release to the customer, a developer will merge all the fixes from several bug branch to trunk and proceed with the normal QA cycle. The problem is that we use trunk as the codebase for our CI job (Hudson, specifically), and therefore, for all commits to the bug branch, it will miss the daily build until it gets merged to trunk when we decided to release the new version of the software. Obviously, that defeats the purpose of having CI. What is the proper way to fix this issue?

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  • Haskell function composition (.) and function application ($) idioms: correct use.

    - by Robert Massaioli
    I have been reading Real World Haskell and I am nearing the end but a matter of style has been niggling at me to do with the (.) and ($) operators. When you write a function that is a composition of other functions you write it like: f = g . h But when you apply something to the end of those functions I write it like this: k = a $ b $ c $ value But the book would write it like this: k = a . b . c $ value Now to me they look functionally equivalent, they do the exact same thing in my eyes. However, the more I look, the more I see people writing their functions in the manner that the book does: compose with (.) first and then only at the end use ($) to append a value to evaluate the lot (nobody does it with many dollar compositions). Is there a reason for using the books way that is much better than using all ($) symbols? Or is there some best practice here that I am not getting? Or is it superfluous and I shouldn't be worrying about it at all? Thanks.

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  • Implementing Tagging System with PHP and mySQL. Caching help!!!

    - by Hamid Sarfraz
    With reference to this post: http://stackoverflow.com/questions/2122546/how-to-implement-tag-counting I have implemented the suggested 3 table tagging system completely. To count the number of Articles per tag, i am using another column named tagArticleCount in the tag definition table. (other columns are tagId, tagText, tagUrl, tagArticleCount). If i implement realtime editing of this table, so that whenever user adds another tag to article or deletes an existing tag, the tag_definition_table is updated to update the counter of the added/removed tag. This will cost an extra query each time any modification is made. (at the same time, related link entry for tag and article is deleted from tagLinkTable). An alternative to this is not allowing any real time editing to the counter, instead use CRONs to update counter of each tag after a specified time period. Here comes the problem that i want to discuss. This can be seen as caching the article count in database. Can you please help me find a way to present the articles in a list when a tag is explored and when the article counter for that tag is not up to date. For example: 1. Counter shows 50 articles, but there are infact 55 entries in the tag link table (that links tags and articles). 2. Counter shows 50 articles, but there are infact 45 extries in the tag link table. How to handle these 2 scenerios given in example. I am going to use APC to keep cache of these counters. Consider it too in your solution. Also discuss performance in the realtime / CRONNED counter updates.

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  • Is concatenating with an empty string to do a string conversion really that bad?

    - by polygenelubricants
    Let's say I have two char variables, and later on I want to concatenate them into a string. This is how I would do it: char c1, c2; // ... String s = "" + c1 + c2; I've seen people who say that the "" + "trick" is "ugly", etc, and that you should use String.valueOf or Character.toString instead. I prefer this construct because: I prefer using language feature instead of API call if possible In general, isn't the language usually more stable than the API? If language feature only hides API call, then even stronger reason to prefer it! More abstract! Hiding is good! I like that the c1 and c2 are visually on the same level String.valueOf(c1) + c2 suggests something is special about c1 It's shorter. Is there really a good argument why String.valueOf or Character.toString is preferrable to "" +? Trivia: in java.lang.AssertionError, the following line appears 7 times, each with a different type: this("" + detailMessage);

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  • Creating an interface and swappable implementations in python

    - by Blankman
    Hi, Would it be possible to create a class interface in python and various implementations of the interface. Example: I want to create a class for pop3 access (and all methods etc.). If I go with a commercial component, I want to wrap it to adhere to a contract. In the future, if I want to use another component or code my own, I want to be able to swap things out and not have things very tightly coupled. Possible? I'm new to python.

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  • What's quicker and better to determine if an array key exists in PHP?

    - by alex
    Consider these 2 examples $key = 'jim'; // example 1 if (isset($array[$key])) { doWhatIWant(); } // example 2 if (array_key_exists($key, $array)) { doWhatIWant(); } I'm interested in knowing if either of these are better. I've always used the first, but have seen a lot of people use the second example on this site. So, which is better? Faster? Clearer intent? Update Thanks for the quality answers. I now understand the difference between the 2. A benchmark states that isset() alone is quicker than array_key_exists(). However, if you want the isset() to behave like array_key_exists() it is slower.

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  • Use of properties vs backing-field inside owner class

    - by whatispunk
    I love auto-implemented properties in C# but lately there's been this elephant standing in my cubicle and I don't know what to do with him. If I use auto-implemented properties (hereafter "aip") then I no longer have a private backing field to use internally. This is fine because the aip has no side-effects. But what if later on I need to add some extra processing in the get or set? Now I need to create a backing-field so I can expand my getters and setters. This is fine for external code using the class, because they won't notice the difference. But now all of the internal references to the aip are going to invoke these side-effects when they access the property. Now all internal access to the once aip must be refactored to use the backing-field. So my question is, what do most of you do? Do you use auto-implemented properties or do you prefer to always use a backing-field? What do you think about properties with side-effects?

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  • When to rewrite vs. upgrade?

    - by MrGumbe
    All custom legacy software needs changing, or so say our users. Sometimes they want a feature or two added and all that is necessary to change a bit of code, add a control, or some other minor upgrade task. Sometimes they want to ditch their error-prone VB5 desktop solution and rewrite the whole thing as a rich Web 2.0 ASP.NET MVC application. More often, however, the scope of changes to legacy functionality lies somewhere between these two extremes. What rules of thumb to you use to decide whether you should upgrade an existing application or start from scratch?

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  • Command Query Separation validating for retries

    - by Neil Barnwell
    So I'm comfortable with the basic concept of CQS, where you might have a command that writes to one database, and that updates the query database that you read from. However, consider the scenario where you are entering data, and want to prevent duplicates. Using new employee data entry an employee register as an example, working through a pile of application forms to key in the new employees' details: Take top sheet. Key in employee name and unique payroll number to UI. Submit. Put paper in "completed pile". Repeat. How would you now prevent the user from keying in the same payroll number again, say for instance if they get distracted and can't remember whether they've keyed one in already and the "message" hasn't got all the way back to the query db for the user to search?

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  • Singleton & Multithreading in Java

    - by vivek jagtap
    What is the preferred way to work with Singleton class in multithreaded environment? Suppose if I have 3 thread, and all they try to access getInstance() method of singleton class at the same time - What would happen if no synchronization is maintained? Is it good practice to use synchronized getInstance() method or use synchronized block inside getInstance(). Please advise if there is any other way out.

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  • Documentation style: how do you differentiate variable names from the rest of the text within a comm

    - by Alix
    Hi, This is a quite superfluous and uninteresting question, I'm afraid, but I always wonder about this. When you're commenting code with inline comments (as opposed to comments that will appear in the generated documentation) and the name of a variable appears in the comment, how do you differentiate it from normal text? E.g.: // Try to parse type. parsedType = tryParse(type); In the comment, "type" is the name of the variable. Do you mark it in any way to signify that it's a symbol and not just part of the comment's text? I've seen things like this: // Try to parse "type". // Try to parse 'type'. // Try to parse *type*. // Try to parse <type>. // Try to parse [type]. And also: // Try to parse variable type. (I don't think the last one is very helpful; it's a bit confusing; you could think "variable" is an adjective there) Do you have any preference? I find that I need to use some kind of marker; otherwise the comments are sometimes ambiguous, or at least force you to reread them when you realise a particular word in the comment was actually the name of a variable. (In comments that will appear in the documentation I use the appropriate tags for the generator, of course: @code, <code></code>, etc) Thanks!

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  • Getting up to speed on modern architecture

    - by Matt Thrower
    Hi, I don't have any formal qualifications in computer science, rather I taught myself classic ASP back in the days of the dotcom boom and managed to get myself a job and my career developed from there. I was a confident and, I think, pretty good programmer in ASP 3 but as others have observed one of the problems with classic ASP was that it did a very good job of hiding the nitty-gritty of http so you could become quite competent as a programmer on the basis of relatively poor understanding of the technology you were working with. When I changed on to .NET at first I treated it like classic ASP, developing stand-alone applications as individual websites simply because I didn't know any better at the time. I moved jobs at this point and spent the next several years working on a single site whose architecture relied heavily on custom objects: in other words I gained a lot of experience working with .NET as a middle-tier development tool using a quite old-fashioned approach to OO design along the lines of the classic "car" class example that's so often used to teach OO. Breaking down programs into blocks of functionality and basing your classes and methods around that. Although we worked under an Agile approach to manage the work the whole setup was classic client/server stuff. That suited me and I gradually got to grips with .NET and started using it far more in the manner that it should be, and I began to see the power inherent in the technology and precisely why it was so much better than good old ASP 3. In my latest job I have found myself suddenly dropped in at the deep end with two quite young, skilled and very cutting-edge programmers. They've built a site architecture which is modelling along a lot of stuff which is new to me and which, in truth I'm having a lot of trouble understanding. The application is built on a cloud computing model with multi-tenancy and the architecture is all loosely coupled using a lot of interfaces, factories and the like. They use nHibernate a lot too. Shortly after I joined, both these guys left and I'm now supposedly the senior developer on a system whose technology and architecture I don't really understand and I have no-one to ask questions of. Except you, the internet. Frankly I feel like I've been pitched in at the deep end and I'm sinking. I'm not sure if this is because I lack the educational background to understand this stuff, if I'm simply not mathematically minded enough for modern computing (my maths was never great - my approach to design is often to simply debug until it works, then refactor until it looks neat), or whether I've simply been presented with too much of too radical a nature at once. But the only way to find out which it is is to try and learn it. So can anyone suggest some good places to start? Good books, tutorials or blogs? I've found a lot of internet material simply presupposes a level of understanding that I just don't have. Your advice is much appreciated. Help a middle-aged, stuck in the mud developer get enthusastic again! Please!

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  • Nested Array with one foreach Loop?

    - by streetparade
    I need to have access to a array which looks like this. Array ( [0] => Array ( [54] => Array ( [test] => 54 [tester] => result ) ) ) foreach($array as $key=>$value) { echo $key;// prints 0 echo $value;// prints Array /* now i can iterate through $value but i dont want it solve that way example: foreach($value as $k=>$v) { echo $k;//prints test echo $v; //prints 54 } */ } How can iterate just once ? to get the values of test and tester? I hope i could explain my problem clear

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  • How to pass non-fatal warnings from a library

    - by wRAR
    A library function parses a file and returns an object. If a parser encounters unknown data, missing values etc., it shouldn't throw an exception and stop parsing (because this is not fatal), but there should be a way to pass information about these things to a caller (so that warnings can be displayed in the UI, for example). How can these warning be returned? I'm thinking of passing a callback function/object into the library, are there any other possible solutions?

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  • Buffering db inserts in multithreaded program

    - by Winter
    I have a system which breaks a large taks into small tasks using about 30 threads as a time. As each individual thread finishes it persists its calculated results to the database. What I want to achieve is to have each thread pass its results to a new persisance class that will perform a type of double buffering and data persistance while running in its own thread. For example, after 100 threads have moved their data to the buffer the persistance class then the persistance class swaps the buffers and persists all 100 entries to the database. This would allow utilization of prepared statements and thus cut way down on the I/O between the program and the database. Is there a pattern or good example of this type of multithreading double buffering?

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  • Why do I need to give my options a value attribute in my dropdown? JQuery.

    - by Alex
    So far in my web developing experiences, I've noticed that almost all web developers/designers choose to give their options in a select a value like so: <select name="foo"> <option value="bar">BarCheese</option> // etc. // etc. </select> Is this because it is best practice to do so? I ask this because I have done a lot of work with jQuery and dropdown's lately, and sometimes I get really annoyed when I have to check something like: $('select[name=foo]').val() == "bar"); To me, many times that seems less clear than just being able to check the val() against BarCheese. So why is it that most web developers/designers specify a value paramater instead of just letting the options actual value be its value?

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  • PHP explode and set to empty string the missing pieces

    - by Marco Demaio
    What's the best way to accomplish the following. I have strings in this format: $s1 = "name1|type1"; //(pipe is the separator) $s2 = "name2|type2"; $s3 = "name3"; //(in some of them type can be missing) Let's assume namen/typen are strings and they can not contain a pipe. Since I need to exctract the name/type separetly, I do: $temp = explode($s1, '|'); $name = $temp[0]; $type = ( isset($temp[1]) ? $temp[1] : '' ); Is there an easier (smarter whatever faster) way to do this without having to do isset($temp[1]) or count($temp). Thanks!

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  • Check if web form values has changed. Best practice

    - by Andrew Florko
    Hello everybody, I have multi-step form and user can navigate to any page to modify or add information. There is a menu that shows progress and steps user completed. This menu allows to navigate to any step user completed or going to complete. Inspite of big button "Save and Continue" some users click this menu to navigate further. I have to check - if values have changed in a form and ask: "Save changes? Yes/No". What is the best way (with minimum code) you suggest me to check if form values have changed. Thank you in advance!

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  • Multiple leaf methods problem in composite pattern

    - by Ondrej Slinták
    At work, we are developing an PHP application that would be later re-programmed into Java. With some basic knowledge of Java, we are trying to design everything to be easily re-written, without any headaches. Interesting problem came out when we tried to implement composite pattern with huge number of methods in leafs. What are we trying to achieve (not using interfaces, it's just an example): class Composite { ... } class LeafOne { public function Foo( ); public function Moo( ); } class LeafTwo { public function Bar( ); public function Baz( ); } $c = new Composite( Array( new LeafOne( ), new LeafTwo( ) ) ); // will call method Foo in all classes in composite that contain this method $c->Foo( ); It seems like pretty much classic Composite pattern, but problem is that we will have quite many leaf classes and each of them might have ~5 methods (of which few might be different than others). One of our solutions, which seems to be the best one so far and might actually work, is using __call magic method to call methods in leafs. Unfortunately, we don't know if there is an equivalent of it in Java. So the actual question is: Is there a better solution for this, using code that would be eventually easily re-coded into Java? Or do you recommend any other solution? Perhaps there's some different, better pattern I could use here. In case there's something unclear, just ask and I'll edit this post.

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