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• How to imitate the workflow view of Automator?

  - by andyfeind

  I’m starting to develop my first full-blown Cocoa application containing a view which I would like to behave (and look) similar to Automator’s AMWorkflowView. The basic features I’d like to achieve: Positioning of subviews Display of subviews in expanded / collapsed states Multiple selection Drag and drop In order to get accustomed to Cocoa, I started with a custom NSView which mainly served as a container for the custom subviews and handled their positioning and multiple selection. The subviews are also subclasses of NSView, and contain a variable amount of views themselves, like buttons, labels and popup menus, and therefore can have different heights. This worked quite well, but before going on, I want to make sure to have everything neat and tidy according to the MVC pattern. I suspect that there already is a class in Cocoa that facilitates the implementation of a view container, like maybe NSCollectionView. It seems that there is no (easy) way to display differently sized views in an NSCollectionView, though. Should I continue implementing my custom NSView (probably using an NSArrayController for selection and sorting support), or are there better ways to go? Any help is much appreciated

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• Teacher confused about MVC?

  - by Gideon

  I have an assignment to create a game in java using MVC as a pattern. The thing is that stuff I read about MVC aren't really what the teacher is telling me. What I read is that the Model are the information objects, they are manipulated by the controllers. So in a game the controller mutates the placement of the objects and check if there is any collision etc. What my teacher told me is that I should put everything that is universal to the platform in the models and the controllers should only tell the model which input is given. That means the game loop will be in a model class, but also collision checks etc. So what I get from his story is that the View is the screen, the Controller is the unput handeler, and the Model is the rest. Can someone point me in the right direction?

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• What is a good architecture for a Lift-JPA application?

  - by egervari

  I was wondering what is the best practice for a JPA model in Lift? I noticed that in the jpa demo application, there is just a Model object that is like a super object that does everything. I don't think this can be the most scalable approach, no? Is it is wise to still do the DAO pattern in Lift? For example, there's some code that looks a tad bloated and could be simplified across all model objects: Model.remove(Model.getReference(classOf[Author], someId)) Could be: AuthorDao.remove(someId) I'd appreciate any tips for setting up something that will work with the way Lift wants to work and is also easy to organize and maintain. Preferably from someone who has actually used JPA on a medium to large Lift site rather than just postulating what Spring does (we know how to do that) ;) The first phase of development will be around 30-40 tables, and will eventually get to over 100... we need a scalable, neat approach.

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• Using MySQL as a job queue

  - by user237815

  I'd like to use MySQL as a job queue. Multiple machines will be producing and consuming jobs. Jobs need to be scheduled; some may run every hour, some every day, etc. It seems fairly straightforward: for each job, have a "nextFireTime" column, and have worker machines search for the job with the nextFireTime, change the status of the record to "inProcess", and then update the nextFireTime when the job ends. The problem comes in when a worker dies silently. It won't be able to update the nextFireTime or set the status back to "idle". Unfortunately, jobs can be long-running, so a reaper thread that looks for jobs that have been inProcess too long isn't an option. There's no timeout value that would work. Can anyone suggest a design pattern that would properly handle unreliable worker machines?

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• Is it inefficient to access a python class member container in a loop statement?

  - by Dave

  Hi there. I'm trying to adopt some best practices to keep my python code efficient. I've heard that accessing a member variable inside of a loop can incur a dictionary lookup for every iteration of the loop, so I cache these in local variables to use inside the loop. My question is about the loop statement itself... if I have the following class: class A(object): def init(self) self.myList = [ 'a','b','c', 'd', 'e' ] Does the following code in a member function incur one, or one-per-loop-iteration (5) dictionary lookups? for letter in self.myList: print letter IE, should I adopt the following pattern, if I am concerned about efficiency... localList = self.myList for letter in localList: print letter or is that actually LESS efficient due to the local variable assign? Note, I am aware that early optimization is a dangerous pitfall if I'm concerned about the overall efficiency of code development. Here I am specifically asking about the efficiency of the code, not the coding. Thanks in advance! D

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• WPF MVVM: How do ViewModels communicate with each other?

  - by Dev1

  I have a View which has 2 sub views on it and a ViewModel is assigned to each view: ViewA - ViewModelA { ViewB - ViewModelB ViewC - ViewModelC } ViewB has a text box and ViewC has a combobox, both of which i need access from ViewModelA. Not the GUI control itself, but the bound value i.e. .Text of the textbox and .SelectedItem of the ComboBox. Currently i just have ViewModelB and ViewModelC as properties on ViewModelA but it feels wrong. What's the standard way for view models to communicate with each other without breaking the MVVM pattern? I'm completely new to WPF/MVVM.

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• ASP.NET MVC Filters: How to set Viewdata for Dropdown based on action parameter

  - by CRice

  Hi, Im loading an entity 'Member' from its id in route data. [ListItemsForMembershipType(true)] public ActionResult Edit(Member someMember) {...} The attribute on the action loads the membership type list items for a dropdown box and sticks it in viewdata. This is fine for add forms, and search forms (it gets all active items) but I need the attribute to execute BASED ON THE VALUE someMember.MembershipTypeId, because its current value must always be present when loading the item (i.e. all active items, plus the one from the loaded record). So the question is, what is the standard pattern for this? How can my attribute accept the value or should I be loading the viewdata for the drop down in a controller supertype or during model binding or something else? It is in an attribute now because the code to set the viewdata would otherwise be duplicated in each usage in each action.

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• Which would be better? Storing/access data in a local text file, or in a database?

  - by TerranRich

  Basically, I'm still working on a puzzle-related website (micro-site really), and I'm making a tool that lets you input a word pattern (e.g. "r??n") and get all the matching words (in this case: rain, rein, ruin, etc.). Should I store the words in local text files (such as words5.txt, which would have a return-delimited list of 5-letter words), or in a database (such as the table Words5, which would again store 5-letter words)? I'm looking at the problem in terms of data retrieval speeds and CPU server load. I could definitely try it both ways and record the times taken for several runs with both methods, but I'd rather hear it from people who might have had experience with this. Which method is generally better overall?

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• What books help one to learn to read code?

  - by Daniel

  Lion's Commentary on Unix Sixth Edition with Source Code is a wonderful book to learn how to read code. Reading code is important -- how does one learn how to write excellent code without having read excellent code? But, sadly, while great writers, of fiction and non-fiction, all spend a great deal of time reading stuff, we, programmers, seem to avoid it like the plague. Worse still, programming books usually go the same way. They might show a pattern or a style, but they often avoid showing good, complex code, and helping one go through it. There are exceptions, of course. I hope. So, with that in mind, what books are to be found which help one learn how to read code?

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• Extract dates from filename

  - by Newbie

  I have a situation where I need to extract dates from the file names whose general pattern is [filename_]YYYYMMDD[.fileExtension] e.g. "xxx_20100326.xls" or x2v_20100326.csv The below program does the work //Number of charecter in the substring is set to 8 //since the length of YYYYMMDD is 8 public static string ExtractDatesFromFileNames(string fileName) { return fileName.Substring(fileName.IndexOf("_") + 1, 8); } Is there any better option of achieving the same? I am basically looking for standard practice. I am using C#3.0 and dotnet framework 3.5 Edit: I have like the solution and the way of answerig of LC. I have used his program like string regExPattern = "^(?:.*_)?([0-9]{4})([0-9]{2})([0-9]{2})(?:\\..*)?$"; string result = Regex.Match(fileName, @regExPattern).Groups[1].Value; The input to the function is : "x2v_20100326.csv" But the output is: 2010 instead of 20100326(which is the expected one). Can anyone please help.

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• Force an object to be allocated on the heap

  - by Warren Seine

  A C++ class I'm writing uses shared_from_this() to return a valid boost::shared_ptr<>. Besides, I don't want to manage memory for this kind of object. At the moment, I'm not restricting the way the user allocates the object, which causes an error if shared_from_this() is called on a stack-allocated object. I'd like to force the object to be allocated with new and managed by a smart pointer, no matter how the user declares it. I thought it could be done through a proxy or an overloaded new operator, but I can't find a proper way of doing that. Is there a common design pattern for such usage? If it's not possible, how can I test it at compile time?

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• MVC - Sanitizing data, where?

  - by dierre

  I'm using CakePHP but it's a question about the MVC pattern. I have in my form the input-text for the tags (separated by commas). To add the tags I've created a Tag model method that basically check if the tag exists and then add the new tag or just a new unit in the tag counter (the Tag model has these fields: id, name, slug, count). In the controller I explode the tags field and pass one tag at a time. The question is: where do I sanitize data? In the controller or in the model method? I think it should be in the controller because that's where I explode but in term of reusability I think I should sanitize data in the model. What do you think?

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• iPhone UIImage number recognition

  - by Skeep

  Hi All, I have a small UIImage (jpg) with a single typed number. I want to be able to read the number with some kind of pattern recognition. I'm really not sure where to start, so any help would be appreciated. my initial idea was to compare this image with other images. For instance compare the image with that of a 1,2,3, etc until a match was found. That just seems slow and cumbersome and wondered if there was a better way to do it? Thanks

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• Google Gears hangs when capturing (unmanaged resource store)

  - by Gus

  Our code was written based on the example from Google Gears' own docs. We're using an unmanaged resource store. So we declare the files in an array, create the store, and capture all the files. Trouble is, the capturing process hangs. It always hangs on a random file (no discernible pattern has emerged), and when you reload the page, it always successfully captures. We're capturing 48 files. It seems to have nothing to do with the files themselves, as it hangs on every file type. I've seen it hang on the 6th file or the 47th. Windows and Mac. FF, IE, and Safari. We are not using a WorkerPool, and I'm thinking this may be necessary. Any other ideas why it would hang?

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• The ** idiom in C++ for object construction

  - by bobobobo

  In a lot of C++ API'S (COM-based ones spring to mind) that make something for you, the pointer to the object that is constructed is usually required as a ** pointer (and the function will construct and init it for you) You usually see signatures like: HRESULT createAnObject( int howbig, Object **objectYouWantMeToInitialize ) ; -- but you seldom see the new object being passed as a return value. Besides people wanting to see error codes, what is the reason for this? Is it better to use the ** pattern rather than a returned pointer for simpler operations such as: wchar_t* getUnicode( const char* src ) ; Or would this better be written as: void getUnicode( const char* src, wchar_t** dst ) ; The most important thing I can think of is to remember to free it, and the ** way, for some reason, tends to remind me that I have to deallocate it as well.

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• Should I always release self for failed init methods?

  - by leo

  Should I always release self when there is a failure inside init, or should I only do so if I have initialized instance variables first? To put it another way, is this pattern valid? Is there a time when I shouldn't release self inside an init method, or should I assume that if the control flow enters init, self has at least a retain count of 1? - (id)init { if ((self = [super init]) == nil) { [self release]; return nil; } //do some init stuff if (somethingFailed) { [self release]; return nil; } return self; }

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• Irregular layout ItemsControl

  - by firoso

  I have a strange layout for an ItemsControl. I have a 4x6 grid with the following pattern: 1 2 3 4 13 14 15 16 5 6 7 8 17 18 19 20 9 10 11 12 21 22 23 24 Is there an easy way to do this? should I be using 6 Items Controls and take "sections" of my list? is there a good way to do this? What about notification? It's important to note that I may, or may not, have all 24 entries present, but the layout needs to be maintained (think of it like filled slots on a bingo card or something)

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• Insert A Line At The Beginnig Of A File

  - by thebourneid

  I'm trying to insert/add a line 'COMMENT DUMMY' at the beginnig of a file as a first row if /PATTERN/ not found. I know how to do this with OPEN CLOSE function. Probably after reading the file it should look something like this: open F, ">", $fn or die "could not open file: $!"; ; print F "COMMENT DUMMY\n", @array; close F; But I have a need to implement this with the use of the Tie::File function and don't know how. use strict; use warnings; use Tie::File; my $fn = 'test.txt'; tie my @lines, 'Tie::File', $fn or die "could not tie file: $!"; untie @lines;

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• How can an Android Service know that its not bound to any Activities

  - by tunneling

  I have an Android Service that I would like to keep running even after the last Activity has been popped off the stack, or the User has chosen to do something else. Essentially the Service is listening for changes on a remote server, and I would like to generate a Notification if and only if an Activity from the app isn't running(or visible). In other words, I don't want the Notifications to occur while the User is directly interacting with the app. In the case where the User is directly interacting with the app, the Service will notify the Activity and update appropriate UI elements based on the changes. I plan to implement this through the Observer pattern. How can the Service know if none of apps Activities are bound to it? Thanks, J

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• How to handle recursive parent/child problems like this?

  - by lsdude

  In web dev I come across these problems a lot. For example, we have a giant list of URLs that are in this format: /businesses /businesses/food /businesses/food/wendys /businesses/food/wendys/chili /businesses/food/wendys/fries /businesses/food/wendys/chicken-nuggets /businesses/pharmacy/cvs /businesses/pharmacy/cvs/toothpaste /businesses/pharmacy/cvs/toothpaste/brand ... and then we need to output each one, where the parent category is in h1 tags, the child is in h2 tags, and the children of that are in h3 tags. I can handle this but I feel my code is messy. I'm sure there is a design pattern I can use? Langs are ruby/php usually. how would you handle this?

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• Interface with inner implementation - good or bad

  - by dermoritz

  I am working on a project with many someInterface - someInterfaceImpl-pairs. Some days ago I got the idea (probably inspired by reading some objective c code) to include the default implementations as an inner class. Now some colleagues (all with much more java experience than me) saw this idea - feedback was between shocked and surprised ("this is working?"). I googled around a bit but didn't find much evidence of usefulness of this "pattern" (personal i like it): pdf-paper and a faq about code style What do you think - especially in those cases where an "default" implementation is tightly coupled to an interface. Update i just found this: Java Interface-Implementation Pair (see accepted answer)

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• Help me understand the code snippet in c#

  - by Benny

  I am reading this blog: Pipes and filters pattern I am confused by this code snippet: public class Pipeline<T> { private readonly List<IOperation<T>> operations = new List<IOperation<T>>(); public Pipeline<T> Register(IOperation<T> operation) { operations.Add(operation); return this; } public void Execute() { IEnumerable<T> current = new List<T>(); foreach (IOperation<T> operation in operations) { current = operation.Execute(current); } IEnumerator<T> enumerator = current.GetEnumerator(); while (enumerator.MoveNext()); } } what is the purpose of this statement: while (enumerator.MoveNext());? seems this code is a noop.

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• interview questions for a test lead

  - by PJ

  Maybe this question has been asked although I didn't find the answer. I am going to attend an interview for a test lead. can you tell me the pattern of questions I will have to face other than the normal question that I was facing previously like What is Software testing? What is Bug life cycle? or Grilling me on my project experience. Also I wnat to know when they are going to hire me for a test lead what would they want to see as an extra add ons?

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• How to get notified about changes of the history via history.pushState?

  - by Felix Kling

  So now that HTML5 introduces history.pushState to change the browsers history, websites start using this in combination with Ajax instead of changing the fragment identifier of the URL. Sadly that means that those calls cannot be detect anymore by onhashchange. My question is: Is there a reliable way (hack? ;)) to detect when a website uses history.pushState? The specification does not state anything about events that are raised (at least I couldn't find anything). I tried to create a facade and replaced window.history with my own JavaScript object, but it didn't have any effect at all. Further explanation: I'm developing a Firefox add-on that needs to detect these changes and act accordingly. I know there was a similar question a few days ago that asked whether listening to some DOM events would be efficient but I would rather not rely on that because these events can be generated for a lot of different reasons. Update: Here is a jsfiddle (use Firefox 4 or Chrome 8) that shows that onpopstate is not triggered when pushState is called (or am I doing something wrong? Feel free to improve it!). Update 2: Another (side) problem is that window.location is not updated when using pushState (but I read about this already here on SO I think).

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• Div horizontal aligning, one fixed, one adaptive

  - by Dorian McHensie

  Hello everyone. I would like to create a vertical splitted site structure using two divs: My intention is to have d2 next to d1 in a horizontal align structure (same line). What i get is not this. In fact using that code, d2 does not take the remaining space, but collapses to the min width. if I use WRONG because d2 goes down and takes all the space (but both divs are in different lines). HOW TO REACH MY OBJECTIVE? Is there a design pattern for this problem???? Thanks.

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