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  • What design pattern will you choose ?

    - by MemoryLeak
    I want to design a class, which contains a procedure to achieve a goal. And it must follow some order to make sure the last method, let's say "ExecuteIt", to behave correctly. in such a case, what design patter will you use ? which can make sure that the user must call the public method according some ordering. If you really don't know what I am saying, then can you share me some concept of choosing a design patter, or what will you consider while design a class?

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  • Factory Method pattern and public constructor

    - by H4mm3rHead
    Hi, Im making a factory method that returns new instances of my objects. I would like to prevent anyone using my code from using a public constructor on my objects. Is there any way of doing this? How is this typically accomplished: public abstract class CarFactory { public abstract ICar CreateSUV(); } public class MercedesFactory : CarFactory { public override ICar CreateSUV() { return new Mercedes4WD(); } } I then would like to limit/prevent the other developers (including me in a few months) from making an instance of Mercedes4WD. But make them call my factory method. How to?

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  • NSString simple pattern matching

    - by SirRatty
    Hi all, Mac OS 10.6, Cocoa project, 10.4 compatibility required. (Please note: my knowledge of regex is quite slight) I need to parse NSStrings, for matching cases where the string contains an embedded tag, where the tag format is: [xxxx] Where xxxx are random characters. e.g. "The quick brown [foxy] fox likes sox". In the above case, I need to grab the string "foxy". (Or nil if no tag is found.) Each string will only have one tag, and the tag can appear anywhere within the string, or may not appear at all. Could someone please help with a way to do that, preferably without having to include another library such as RegexKit. Thank you for any help.

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  • Software Architecture: Unit of Work design pattern discussion

    - by santiagobasulto
    Hey everybody. According Martin Fowler's Unit of Work description: "Maintains a list of objects that are affected by a business transaction and coordinates the writing out of changes and resolution of concurrency problems." Avoiding very small calls to the database, which ends up being very slow I'm wondering. If we just delimit it to database transaction management, won't prepare statements help with this?

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  • Apply PHP regex replace on a multi-line repeted pattern

    - by Hussain
    Let's say I have this input: I can haz a listz0rs! # 42 # 126 I can haz another list plox? # Hello, world! # Welcome! I want to split it so that each set of hash-started lines becomes a list: I can haz a listz0rs! <ul> <li>42</li> <li>126</li> </ul> I can haz another list plox? <ul> <li>Hello, world!</li> <li>Welcome!</li> </ul> If I run the input against the regex "/(?:(?:(?<=^# )(.*)$)+)/m", I get the following result: Array ( [0] => Array ( [0] => 42 ) Array ( [0] => 126 ) Array ( [0] => Hello, world! ) Array ( [0] => Welcome! ) ) This is fine and dandy, but it doesn't distinguish between the two different lists. I need a way to either make the quantifier return a concatenated string of all the occurrences, or, ideally, an array of all the occurrences. Idealy, this should be my output: Array ( [0] = Array ( [0] = 42 [1] = 126 ) Array ( [0] = Hello, world! [1] = Welcome! ) ) Is there any way of achieving this, and if not, is there a close alternative? Thanks in advance!

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  • Regex and Pattern Matching in Scala

    - by Bruce Ferguson
    I am not strong in regex, and pretty new to Scala. I would like to be able to find a match between the first letter of a word, and one of the letters in a group such as "ABC". In pseudocode, this might look something like: case Process(word) => word.firstLetter match { case([a-c][A-C]) => case _ => } } but I don't know how to grab the first letter in Scala instead of Java, how to express the regular expression properly, nor if it's possible to do this within a case class. Any suggestions? Thanks in advance. Bruce

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  • Apply PHP regex replace on a multi-line repeated pattern

    - by Hussain
    Let's say I have this input: I can haz a listz0rs! # 42 # 126 I can haz another list plox? # Hello, world! # Welcome! I want to split it so that each set of hash-started lines becomes a list: I can haz a listz0rs! <ul> <li>42</li> <li>126</li> </ul> I can haz another list plox? <ul> <li>Hello, world!</li> <li>Welcome!</li> </ul> If I run the input against the regex "/(?:(?:(?<=^# )(.*)$)+)/m", I get the following result: Array ( [0] => Array ( [0] => 42 ) [1] => Array ( [0] => 126 ) [2] => Array ( [0] => Hello, world! ) [3] => Array ( [0] => Welcome! ) ) This is fine and dandy, but it doesn't distinguish between the two different lists. I need a way to either make the quantifier return a concatenated string of all the occurrences, or, ideally, an array of all the occurrences. Ideally, this should be my output: Array ( [0] => Array ( [0] => 42 [1] => 126 ) [1] => Array ( [0] => Hello, world! [1] => Welcome! ) ) Is there any way of achieving this, and if not, is there a close alternative? Thanks in advance!

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  • How to index a date column with null values?

    - by Heinz Z.
    How should I index a date column when some rows has null values? We have to select rows between a date range and rows with null dates. We use Oracle 9.2 and higher. Options I found Using a bitmap index on the date column Using an index on date column and an index on a state field which value is 1 when the date is null Using an index on date column and an other granted not null column My thoughts to the options are: to 1: the table have to many different values to use an bitmap index to 2: I have to add an field only for this purpose and to change the query when I want to retrieve the null date rows to 3: locks tricky to add an field to an index which is not really needed What is the best practice for this case? Thanks in advance Some infos I have read: Oracle Date Index When does Oracle index null column values?

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  • How to get the first non-null value in Java?

    - by froadie
    Is there a Java equivalent of SQL's COALESCE function? That is, is there any way to return the first non-null value of several variables? e.g. Double a = null; Double b = 4.4; Double c = null; I want to somehow have a statement that will return the first non-null value of a, b, and c - in this case, it would return b, or 4.4. (Something like the sql method - return COALESCE(a,b,c)). I know that I can do it explicitly with something like: return a != null ? a : (b != null ? b : c) But I wondered if there was any built-in, accepted function to accomplish this.

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  • Complex pattern replacement using PHP preg_replace function ignoring quoted strings

    - by Saiful
    Consider the following string: this is a STRING WHERE some keywords ARE available. 'i need TO format the KEYWORDS from the STRING' In the above string keywords are STRING and WHERE Now i need to get an output as follows: this is a <b>STRING</b> <b>WHERE</b> some keywords ARE available. 'i need TO format the KEYWORDS from the STRING' So that the html output will be like: this is a STRING WHERE some keywords ARE available. 'i need TO format the KEYWORDS from the STRING' Note that the keywords within a quoted ('...') string will be ignored. in the above example i ignored the STRING keyword within the quoted string. Please give a modified version of the following PHP script so that I can have my desired result as above : $patterns = array('/STRING/','/WHERE/'); $replaces = array('<b>STRING</b>', '<b>WHERE</b>'); $string = "this is a STRING WHERE some keywords ARE available. 'i need TO format the KEYWORDS from the STRING'"; preg_replace($patterns, $replaces, $string);

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  • Get class instance by class name string

    - by VDVLeon
    Hi all, I noticed the function Object.factory(char[] className) in D. But it does not work like I hoped it would work; it does not work ;) An example: import std.stdio; class TestClass { override string toString() { return typeof(this).stringof; // TestClass } }; void main(string[] args) { auto i = Object.factory("TestClass"); if (i is null) { writeln("Class not found"); } else { writeln("Class string: " ~ i); } } I think this should result in the message: "Class string: TestClass" but it says "Class not found". Does anybody know why this happens and how I could fix it ? Or do I need to make my own class factory. For example by make a class with a static array Object[string] classes; with class instances. When I want a new instance I do this: auto i = (className in classes); if (i is null) { return null; } return i.classinfo.create();

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  • java - check if string ends with certain pattern

    - by The Learner
    I have string like: This.is.a.great.place.too.work. (or) This/is/a/great/place/too/work/ than my java program should give me that the sentence is valid and it has "work". if i Have : This.is.a.great.place.too.work.hahahha (or) This/is/a/great/place/too/work/hahahah Should not give me that there is a work in the sentance. so I am looking at java strings to find a word at the end of the sentance having . (or),(or)/ before it. How can I achieve that

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  • Best Practice, objects design ASP.NET MVC

    - by DoomStone
    Hello Stackoverflow I have a code design question that have been torbeling me for a while, you see I’m doing a refactoring of my website Cosplay Denmark, a site where cospalyers can upload images of them self in their costumes. The original site was done in php, Zend MVC, but my refactoring is being done in ASP.NET MVC 2. If you take the site http://www.cosplaydanmark.dk/Costumes/ (You can switch to English in the left column (Sprog)) Here you see a list of all the anime’s we have on the site with images, we show the name, how many different characters and how many images there are under this anime. http://www.cosplaydanmark.dk/Costumes/Bleach If you click on an anime will you get a list of characters within the given anime which we have images in, here do we show the character name, how many galleries and how many images. http://www.cosplaydanmark.dk/Costumes/Bleach/Ichigo_Kurosaki/ If you click on the character name, will you get a list of the galleries under the given character in the given anime. Here we have some information about the gallery, such as image count. http://www.cosplaydanmark.dk/Costumes/Bleach/Ichigo_Kurosaki/Admi/ Should you click the gallery do you get a list of the images in the gallery. My database look like this at the moment. As you can might imagine there are a lot of different query’s to create the site, on the first site I need to do a select on the on the “animes” table and for each result, I need to do a count select on characters and galleries. My plan to create this will be one of the following Where the IList, would be a lazy load list. But I can’t decide what would be the best solution for this would be, also if there is a better way of doing this. My priority is to have good performance with a minimum lose of features and code upkeep. I’m using a service pattern with a linq to sql repository. My design is not absolute, I’m willing to change it if it could increase performance :D I hope that I have describe my question good enough for you to understand what I mean, but ask away if there are anything I have missed.

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  • Deriving an HTMLElement Object from jQuery Object

    - by Jasconius
    I'm doing a fairly exhaustive series of DOM manipulations where a few elements (specifically form elements) have some events. I am dynamically creating (actually cloning from a source element) several boxes and assigning a change() event to them. The change event executes, and within the context of the event, "this" is the HTML Element Object. What I need to do at this point however is determine a contact for this HTML Element Object. I have these objects stored already as jQuery entities in assorted arrays, but obviously [HTMLElement Object] != [Object Object] And the trick is that I cannot cast $(this) and make a valid comparison since that would create a new object and the pointer would be different. So... I've been banging my head against this for a while. In the past I've been able to circumvent this problem by doing an innerHTML comparison, but in this case the objects I am comparing are 100% identical, just there's lots of them. Therefore I need a solid comparison. This would be easy if I could somehow derive the HTMLElement object from my originating jQuery object. Thoughts, other ideas? Help. :(

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  • Convert JSON flattened for forms back to an object

    - by George Jempty
    I am required (please therefore no nit-picking the requirement, I've already nit-picked it, and this is the req) to convert certain form fields that have "object nesting" embedded in the field names, back to the object(s) themselves. Below are some typical form field names: phones_0_patientPhoneTypeId phones_0_phone phones_1_patientPhoneTypeId phones_1_phone The form fields above were derived from an object such as the one toward the bottom (see "Data"), and that is the format of the object I need to reassemble. It can be assumed that any form field with a name that contains the underscore _ character needs to undergo this conversion. Also that the segment of the form field between underscores, if numeric, signifies a Javascript array, otherwise an object. I found it easy to devise a (somewhat naive) implementation for the "flattening" of the original object for use by the form, but am struggling going in the other direction; below the object/data below I'm pasting my current attempt. One problem (perhaps the only one?) with it is that it does not currently properly account for array indexes, but this might be tricky because the object will subsequently be encoded as JSON, which will not account for sparse arrays. So if "phones_1" exists, but "phones_0" does not, I would nevertheless like to ensure that a slot exists for phones[0] even if that value is null. Implementations that tweak what I have begun, or are entirely different, encouraged. If interested let me know if you'd like to see my code for the "flattening" part that is working. Thanks in advance Data: var obj = { phones: [{ "patientPhoneTypeId": 4, "phone": "8005551212" }, { "patientPhoneTypeId": 2, "phone": "8885551212" }]}; Code to date: var unflattened = {}; for (var prop in values) { if (prop.indexOf('_') > -1) { var lastUnderbarPos = prop.lastIndexOf('_'); var nestedProp = prop.substr(lastUnderbarPos + 1); var nesting = prop.substr(0, lastUnderbarPos).split("_"); var nestedRef, isArray, isObject; for (var i=0, n=nesting.length; i<n; i++) { if (i===0) { nestedRef = unflattened; } if (i < (n-1)) { // not last if (/^\d+$/.test(nesting[i+1])) { isArray = true; isObject = false; } else { isArray = true; isObject = false; } var currProp = nesting[i]; if (!nestedRef[currProp]) { if (isArray) { nestedRef[currProp] = []; } else if (isObject) { nestedRef[currProp] = {}; } } nestedRef = nestedRef[currProp]; } else { nestedRef[nestedProp] = values[prop]; } } }

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  • Using an object in an if statement... (Android)

    - by James Rattray
    I have an object variable Object test = Spinner.getSelectedItem(); -It gets the selected item from the Spinner (called spinner) and names the item 'test' I want to do an if statement related to that object e.g: 'if (test = "hello") { //do something }' But it appears not to work.... Can someone give me some help? -Do I have to use a different if? or convert the object to string etc.? Thanks alot... James

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  • Scala passing type parameters to object

    - by Shahzad Mian
    In Scala v 2.7.7 I have a file with class Something[T] extends Other { } object Something extends OtherConstructor[Something] { } This throws the error: class Something takes type parameters object Something extends OtherConstructor[Something] { However, I can't do this object Something[T] extends OtherConstructor[Something[T]] { } It throws an error: error: ';' expected but '[' found. Is it possible to send type parameters to object? Or should I change and simply use Otherconstructor

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  • Code Contracts Vs. Object Initializers (.net 4.0)

    - by Mystagogue
    At face value, it would seem that object initializers present a problem for .net 4.0 "code contracts", where normally the invariant should be established by the time the object constructor is finished. Presumably, however, object-initializers require properties to be set after construction is complete. My question is if the invariants of "code contracts" are able to handle object initializers, "as if" the properties were set before the constructor completes? That would be very nice indeed!!

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  • Does my use of the strategy pattern violate the fundamental MVC pattern in iOS?

    - by Goodsquirrel
    I'm about to use the 'strategy' pattern in my iOS app, but feel like my approach violates the somehow fundamental MVC pattern. My app is displaying visual "stories", and a Story consists (i.e. has @properties) of one Photo and one or more VisualEvent objects to represent e.g. animated circles or moving arrows on the photo. Each VisualEvent object therefore has a eventType @property, that might be e.g. kEventTypeCircle or kEventTypeArrow. All events have things in common, like a startTime @property, but differ in the way they are being drawn on the StoryPlayerView. Currently I'm trying to follow the MVC pattern and have a StoryPlayer object (my controller) that knows about both the model objects (like Story and all kinds of visual events) and the view object StoryPlayerView. To chose the right drawing code for each of the different visual event types, my StoryPlayer is using a switch statement. @implementation StoryPlayer // (...) - (void)showVisualEvent:(VisualEvent *)event onStoryPlayerView:storyPlayerView { switch (event.eventType) { case kEventTypeCircle: [self showCircleEvent:event onStoryPlayerView:storyPlayerView]; break; case kEventTypeArrow: [self showArrowDrawingEvent:event onStoryPlayerView:storyPlayerView]; break; // (...) } But switch statements for type checking are bad design, aren't they? According to Uncle Bob they lead to tight coupling and can and should almost always be replaced by polymorphism. Having read about the "Strategy"-Pattern in Head First Design Patterns, I felt this was a great way to get rid of my switch statement. So I changed the design like this: All specialized visual event types are now subclasses of an abstract VisualEvent class that has a showOnStoryPlayerView: method. @interface VisualEvent : NSObject - (void)showOnStoryPlayerView:(StoryPlayerView *)storyPlayerView; // abstract Each and every concrete subclass implements a concrete specialized version of this drawing behavior method. @implementation CircleVisualEvent - (void)showOnStoryPlayerView:(StoryPlayerView *)storyPlayerView { [storyPlayerView drawCircleAtPoint:self.position color:self.color lineWidth:self.lineWidth radius:self.radius]; } The StoryPlayer now simply calls the same method on all types of events. @implementation StoryPlayer - (void)showVisualEvent:(VisualEvent *)event onStoryPlayerView:storyPlayerView { [event showOnStoryPlayerView:storyPlayerView]; } The result seems to be great: I got rid of the switch statement, and if I ever have to add new types of VisualEvents in the future, I simply create new subclasses of VisualEvent. And I won't have to change anything in StoryPlayer. But of cause this approach violates the MVC pattern since now my model has to know about and depend on my view! Now my controller talks to my model and my model talks to the view calling methods on StoryPlayerView like drawCircleAtPoint:color:lineWidth:radius:. But this kind of calls should be controller code not model code, right?? Seems to me like I made things worse. I'm confused! Am I completely missing the point of the strategy pattern? Is there a better way to get rid of the switch statement without breaking model-view separation?

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  • So what *did* Alan Kay really mean by the term "object-oriented"?

    - by Charlie Flowers
    Reportedly, Alan Kay is the inventor of the term "object oriented". And he is often quoted as having said that what we call OO today is not what he meant. For example, I just found this on Google: I made up the term 'object-oriented', and I can tell you I didn't have C++ in mind -- Alan Kay, OOPSLA '97 I vaguely remember hearing something pretty insightful about what he did mean. Something along the lines of "message passing". Do you know what he meant? Can you fill in more details of what he meant and how it differs from today's common OO? Please share some references if you have any. Thanks.

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  • Why should ViewModel route actions to Controller when using the MVCVM pattern?

    - by Lea Hayes
    When reading examples across the Internet (including the MSDN reference) I have found that code examples are all doing the following type of thing: public class FooViewModel : BaseViewModel { public FooViewModel(FooController controller) { Controller = controller; } protected FooController Controller { get; private set; } public void PerformSuperAction() { // This just routes action to controller... Controller.SuperAction(); } ... } and then for the view: public class FooView : BaseView { ... private void OnSuperButtonClicked() { ViewModel.PerformSuperAction(); } } Why do we not just do the following? public class FooView : BaseView { ... private void OnSuperButtonClicked() { ViewModel.Controller.SuperAction(); // or, even just use a shortcut property: Controller.SuperAction(); } }

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  • Parallel Class/Interface Hierarchy with the Facade Design Pattern?

    - by Mike G
    About a third of my code is wrapped inside a Facade class. Note that this isn't a "God" class, but actually represents a single thing (called a Line). Naturally, it delegates responsibilities to the subsystem behind it. What ends up happening is that two of the subsystem classes (Output and Timeline) have all of their methods duplicated in the Line class, which effectively makes Line both an Output and a Timeline. It seems to make sense to make Output and Timeline interfaces, so that the Line class can implement them both. At the same time, I'm worried about creating parallel class and interface structures. You see, there are different types of lines AudioLine, VideoLine, which all use the same type of Timeline, but different types of Output (AudioOutput and VideoOutput, respectively). So that would mean that I'd have to create an AudioOutputInterface and VideoOutputInterface as well. So not only would I have to have parallel class hierarchy, but there would be a parallel interface hierarchy as well. Is there any solution to this design flaw? Here's an image of the basic structure (minus the Timeline class, though know that each Line has-a Timeline): NOTE: I just realized that the word 'line' in Timeline might make is sound like is does a similar function as the Line class. They don't, just to clarify.

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  • Where, in an object oriented system should you, if at all, choose (C-style) structs over classes?

    - by Anto
    C and most likely many other languages provide a struct keyword for creating structures (or something in a similar fashion). These are (at least in C), from a simplified point of view like classes, but without polymorphism, inheritance, methods, and so on. Think of an object-oriented (or multi paradigm) language with C-style structs. Where would you choose them over classes? Now, I don't believe they are to be used with OOP as classes seem to replace their purposes, but I wonder if there are situations where they could be preferred over classes in otherwise object-oriented programs and in what kind of situations. Are there such situations?

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