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  • How to design Models the correct way: Object-oriented or "Package"-oriented?

    - by ajsie
    I know that in OOP you want every object (from a class) to be a "thing", eg. user, validator etc. I know the basics about MVC, how they different parts interact with each other. However, i wonder if the models in MVC should be designed according to the traditional OOP design, that is to say, should every model be a database/table/row (solution 2)? Or is the intention more like to collect methods that are affecting the same table or a bunch of related tables (solution 1). example for an Address book module in CodeIgniter, where i want be able to "CRUD" a Contact and add/remove it to/from a CRUD-able Contact Group. Models solution 1: bunching all related methods together (not real object, rather a "package") class Contacts extends Model { function create_contact() {) function read_contact() {} function update_contact() {} function delete_contact() {} function add_contact_to_group() {} function delete_contact_from_group() {} function create_group() {} function read_group() {} function update_group() {} function delete_group() {} } Models solution 2: the OOP way (one class per file) class Contact extends Model { private $name = ''; private $id = ''; function create_contact() {) function read_contact() {} function update_contact() {} function delete_contact() {} } class ContactGroup extends Model { private $name = ''; private $id = ''; function add_contact_to_group() {} function delete_contact_from_group() {} function create_group() {} function read_group() {} function update_group() {} function delete_group() {} } i dont know how to think when i want to create the models. and the above examples are my real tasks for creating an Address book. Should i just bunch all functions together in one class. then the class contains different logic (contact and group), so it can not hold properties that are specific for either one of them. the solution 2 works according to the OOP. but i dont know why i should make such a dividing. what would the benefits be to have a Contact object for example. Its surely not a User object, so why should a Contact "live" with its own state (properties and methods). you experienced guys with OOP/MVC, please shed a light on how one should think here in this very concrete task.

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  • loops and conditionals inside triggers

    - by Ying
    I have this piece of logic I would like to implement as a trigger, but I have no idea how to do it! I want to create a trigger that, when a row is deleted, it checks to see if the value of one of its columns exists in another table, and if it does, it should also perform a delete on another table based on another column. So say we had a table Foo that has columns Bar, Baz. This is what id be doing if i did not use a trigger: function deleteFromFooTable(FooId) { SELECT (Bar,Baz) FROM FooTable WHERE id=FooId if not-empty(SELECT * FROM BazTable WHERE id=BazId) DELETE FROM BarTable WHERE id=BarId DELETE FROM FooTable WHERE id=FooId } I jumped some hoops in that pseudo code, but i hope you all get where im going. It seems what i would need is a way to do conditionals and to loop(in case of multiple row deletes?) in the trigger statement. So far, I haven't been able to find anything. Is this not possible, or is this bad practice? Thanks!

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  • PL/SQL - How to pull data from 3 tables based on latest created date

    - by Nancy
    Hello, I'm hoping someone can help me as I've been stuck on this problem for a few days now. Basically I'm trying to pull data from 3 tables in Oracle: 1) Orders Table 2) Vendor Table and 3) Master Data Table. Here's what the 3 tables look like: Table 1: BIZ_DOC2 (Orders table) OBJECTID (Unique key) UNIQUE_DOC_NAME (Document Name i.e. ORD-005) CREATED_AT (Date the order was created) Table 2: UDEF_VENDOR (Vendors Table): PARENT_OBJECT_ID (This matches up to the ObjectId in the Orders table) VENDOR_OBJECT_NAME (This is the name of the vendor i.e. Acme) Table 3: BIZ_UNIT (Master Data table) PARENT_OBJECT_ID (This matches up to the ObjectID in the Orders table) BIZ_UNIT_OBJECT_NAME (This is the name of the business unit i.e. widget A, widget B) Note: The Vendors Table and Master Data do not have a link between them except through the Orders table. I can join all of the data from the tables and it looks something like this: Before selecting latest order date: ORD-005 | Widget A | Acme | 3/14/10 ORD-005 | Widget B | Acme | 3/14/10 ORD-004 | Widget C | Acme | 3/10/10 Ideally I'd like to return the latest order for each vendor. However, each order may contain multiple business units (e.g. types of widgets) so if a Vendor's latest record is ORD-005 and the order contains 2 business units, here's what the result set should look like by the following columns: UNIQUE_DOC_NAME, BIZ_UNIT_OBJECT_NAME, VENDOR_OBJECT_NAME, CREATED_AT After selecting by latest order date: ORD-005 | Widget A | Acme | 3/14/10 ORD-005 | Widget B | Acme | 3/14/10 I tried using Select Max and several variations of sub-queries but I just can't seem to get it working. Any help would be hugely appreciated!

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  • How much of STL is too much?

    - by Darius Kucinskas
    I am using a lot of STL code with std::for_each, bind, and so on, but I noticed that sometimes STL usage is not good idea. For example if you have a std::vector and want to do one action on each item of the vector, your first idea is to use this: std::for_each(vec.begin(), vec.end(), Foo()) and it is elegant and ok, for a while. But then comes the first set of bug reports and you have to modify code. Now you should add parameter to call Foo(), so now it becomes: std::for_each(vec.begin(), vec.end(), std::bind2nd(Foo(), X)) but that is only temporary solution. Now the project is maturing and you understand business logic much better and you want to add new modifications to code. It is at this point that you realize that you should use old good: for(std::vector::iterator it = vec.begin(); it != vec.end(); ++it) Is this happening only to me? Do you recognise this kind of pattern in your code? Have you experience similar anti-patterns using STL?

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  • How can I make this method more Scalalicious

    - by Neil Chambers
    I have a function that calculates the left and right node values for some collection of treeNodes given a simple node.id, node.parentId association. It's very simple and works well enough...but, well, I am wondering if there is a more idiomatic approach. Specifically is there a way to track the left/right values without using some externally tracked value but still keep the tasty recursion. /* * A tree node */ case class TreeNode(val id:String, val parentId: String){ var left: Int = 0 var right: Int = 0 } /* * a method to compute the left/right node values */ def walktree(node: TreeNode) = { /* * increment state for the inner function */ var c = 0 /* * A method to set the increment state */ def increment = { c+=1; c } // poo /* * the tasty inner method * treeNodes is a List[TreeNode] */ def walk(node: TreeNode): Unit = { node.left = increment /* * recurse on all direct descendants */ treeNodes filter( _.parentId == node.id) foreach (walk(_)) node.right = increment } walk(node) } walktree(someRootNode) Edit - The list of nodes is taken from a database. Pulling the nodes into a proper tree would take too much time. I am pulling a flat list into memory and all I have is an association via node id's as pertains to parents and children. Adding left/right node values allows me to get a snapshop of all children (and childrens children) with a single SQL query. The calculation needs to run very quickly in order to maintain data integrity should parent-child associations change (which they do very frequently). In addition to using the awesome Scala collections I've also boosted speed by using parallel processing for some pre/post filtering on the tree nodes. I wanted to find a more idiomatic way of tracking the left/right node values. After looking at the answers listed I have settled on this synthesised version: def walktree(node: TreeNode) = { def walk(node: TreeNode, counter: Int): Int = { node.left = counter node.right = treeNodes .filter( _.parentId == node.id) .foldLeft(counter+1) { (counter, curnode) => walk(curnode, counter) + 1 } node.right } walk(node,1) }

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  • Can the Singleton be replaced by Factory?

    - by lostiniceland
    Hello Everyone There are already quite some posts about the Singleton-Pattern around, but I would like to start another one on this topic since I would like to know if the Factory-Pattern would be the right approach to remove this "anti-pattern". In the past I used the singleton quite a lot, also did my fellow collegues since it is so easy to use. For example, the Eclipse IDE or better its workbench-model makes heavy usage of singletons as well. It was due to some posts about E4 (the next big Eclipse version) that made me start to rethink the singleton. The bottom line was that due to this singletons the dependecies in Eclipse 3.x are tightly coupled. Lets assume I want to get rid of all singletons completely and instead use factories. My thoughts were as follows: hide complexity less coupling I have control over how many instances are created (just store the reference I a private field of the factory) mock the factory for testing (with Dependency Injection) when it is behind an interface In some cases the factories can make more than one singleton obsolete (depending on business logic/component composition) Does this make sense? If not, please give good reasons for why you think so. An alternative solution is also appreciated. Thanks Marc

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  • C#: How to run NUnit from my code

    - by Flavio
    Hello, I'd like to use NUnit to run unit tests in my plug-in, but it needs to be run in the context of my application. To solve this, I was trying to develop a plug-in that runs NUnit, which in turn will execute my tests in the application's context. I didn't find a specific documentation on this subject so I dug a piece of information here and there and I came out with the following piece of code (which is similar to one I found here in StackOverflow): SimpleTestRunner runner = new SimpleTestRunner(); TestPackage package = new TestPackage( "Test" ); string loc = Assembly.GetExecutingAssembly().Location package.Assemblies.Add( loc ); if( runner.Load(package) ) { TestResult result = runner.Run( new NullListener() ); } The result variable says "has no TestFixture" although I know for sure it is there. In fact my test file contains two test. Using another approach I found, which is summarized by the following code: TestSuiteBuilder builder = new TestSuiteBuilder(); TestSuite testSuite = builder.Build( package ); // Run tests TestResult result = testSuite.Run( new NullListener(), NUnit.Core.TestFilter.Empty ); I saw nunit data structures with only 1 test and I had the same error. For sake of completeness, I am using the latest version of nunit, which is 2.5.5.10112. Does anyone know what I'm missing? A sample code would be appreciated. thanks

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  • Optimal two variable linear regression SQL statement (censoring outliers)

    - by Dave Jarvis
    Problem Am looking to apply the y = mx + b equation (where m is SLOPE, b is INTERCEPT) to a data set, which is retrieved as shown in the SQL code. The values from the (MySQL) query are: SLOPE = 0.0276653965651912 INTERCEPT = -57.2338357550468 SQL Code SELECT ((sum(t.YEAR) * sum(t.AMOUNT)) - (count(1) * sum(t.YEAR * t.AMOUNT))) / (power(sum(t.YEAR), 2) - count(1) * sum(power(t.YEAR, 2))) as SLOPE, ((sum( t.YEAR ) * sum( t.YEAR * t.AMOUNT )) - (sum( t.AMOUNT ) * sum(power(t.YEAR, 2)))) / (power(sum(t.YEAR), 2) - count(1) * sum(power(t.YEAR, 2))) as INTERCEPT FROM (SELECT D.AMOUNT, Y.YEAR FROM CITY C, STATION S, YEAR_REF Y, MONTH_REF M, DAILY D WHERE -- For a specific city ... -- C.ID = 8590 AND -- Find all the stations within a 15 unit radius ... -- SQRT( POW( C.LATITUDE - S.LATITUDE, 2 ) + POW( C.LONGITUDE - S.LONGITUDE, 2 ) ) <15 AND -- Gather all known years for that station ... -- S.STATION_DISTRICT_ID = Y.STATION_DISTRICT_ID AND -- The data before 1900 is shaky; insufficient after 2009. -- Y.YEAR BETWEEN 1900 AND 2009 AND -- Filtered by all known months ... -- M.YEAR_REF_ID = Y.ID AND -- Whittled down by category ... -- M.CATEGORY_ID = '001' AND -- Into the valid daily climate data. -- M.ID = D.MONTH_REF_ID AND D.DAILY_FLAG_ID <> 'M' GROUP BY Y.YEAR ORDER BY Y.YEAR ) t Data The data is visualized here (with five outliers highlighted): Questions How do I return the y value against all rows without repeating the same query to collect and collate the data? That is, how do I "reuse" the list of t values? How would you change the query to eliminate outliers (at an 85% confidence interval)? The following results (to calculate the start and end points of the line) appear incorrect. Why are the results off by ~10 degrees (e.g., outliers skewing the data)? (1900 * 0.0276653965651912) + (-57.2338357550468) = -4.66958228 (2009 * 0.0276653965651912) + (-57.2338357550468) = -1.65405406 I would have expected the 1900 result to be around 10 (not -4.67) and the 2009 result to be around 11.50 (not -1.65). Thank you!

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  • NHibernate Session DI from StructureMap in components

    - by Corey Coogan
    I know this is somewhat of a dead horse, but I'm not finding a satisfactory answer. First let me say, I am NOT dealing with a web app, otherwise managing NH Session is quite simple. I have a bunch of enterprise components. Those components have their own service layer that will act on multiple repositories. For example: Claim Component Claim Processing Service Claim Repository Billing Component Billing Service Billing REpository Policy Component PolicyLockService Policy Repository Now I may have a console, or windows application that needs to coordinate an operation that involves each of the services. I want to write the services to be injected with (DI) their required repositories. The Repositories should have an ISession, or similar, injected into them so that I can have this operation performed under one ISession/ITransaction. I'm aware of the Unit Of Work pattern and the many samples out there, but none of them showed DI. I'm also leery of [ThreadStatic] because this stuff can also be used from WCF and I have found enough posts describing how to do that. I've read about Business Conversations, but need something simple that each windows/console app can easily bootstrap since we have alot of these apps and some pretty inexperienced developers. So how can I configure StructureMap to inject the same ISession into each of the dependent repositories from an application? Here's a totally contrived and totally made up example without using SM (for clarification only - please don't spend energy critisizing): ConsoleApplication Main { using(ISession session = GetSession()) using(ITransaction trans = session.BeginTransaction()) { var policyRepo = new PolicyRepo(session); var policyService = new PolicyService(policyRepo); var billingRepo = new BillingRepo(session) var billingService = new BillingService(billingRepo); var claimRepo = new ClaimsRepo(session); var claimService = new ClaimService(claimRepo, policyService, billingService); claimService.FileCLaim(); trans.Commit(); } }

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  • How do I properly implement a property in F#?

    - by Greg D
    Consider my first attempt, a simple type in F# like the following: type Test() = inherit BaseImplementingNotifyPropertyChangedViaOnPropertyChanged() let mutable prop: string = null member this.Prop with public get() = prop and public set value = match value with | _ when value = prop -> () | _ -> let prop = value this.OnPropertyChanged("Prop") Now I test this via C# (this object is being exposed to a C# project, so apparent C# semantics are desirable): [TestMethod] public void TaskMaster_Test() { var target = new FTest(); string propName = null; target.PropertyChanged += (s, a) => propName = a.PropertyName; target.Prop = "newString"; Assert.AreEqual("Prop", propName); Assert.AreEqual("newString", target.Prop); return; } propName is properly assigned, my F# Setter is running, but the second assert is failing because the underlying value of prop isn't changed. This sort of makes sense to me, because if I remove mutable from the prop field, no error is generated (and one should be because I'm trying to mutate the value). I think I must be missing a fundamental concept. What's the correct way to rebind/mutate prop in the Test class so that I can pass my unit test?

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  • using EventToCommand & PassEventArgsToCommand :: how to get sender, or better metaphor?

    - by JoeBrockhaus
    The point of what I'm doing is that there are a lot of things that need to happen in the viewmodel, but when the view has been loaded, not on constructor. I could wire up event handlers and send messages, but that just seems kinda sloppy to me. I'm implementing a base view and base viewmodel where this logic is contained so all my views get it by default, hopefully. Perhaps I can't even get what I'm wanting: the sender. I just figured this is what RoutedEventArgs.OriginalSource was supposed to be? [Edit] In the meantime, I've hooked up an EventHandler in the xaml.cs, and sure enough, OriginalSource is null there as well. So I guess really I need to know if it's possible to get a reference to the view/sender in the Command as well? [/Edit] My implementation requires that a helper class to my viewmodels which is responsible for creating 'windows' knows of the 'host' control that all the windows get added to. i'm open to suggestions for accomplishing this outside the scope of using eventtocommand. :) (the code for Unloaded is the same) #region ViewLoadedCommand private RelayCommand<RoutedEventArgs> _viewLoadedCommand = null; /// <summary> /// Command to handle the control's Loaded event. /// </summary> public RelayCommand<RoutedEventArgs> ViewLoadedCommand { get { // lazy-instantiate the RelayCommand on first usage if (_viewLoadedCommand == null) { _viewLoadedCommand = new RelayCommand<RoutedEventArgs>( e => this.OnViewLoadedCommand(e)); } return _viewLoadedCommand; } } #endregion ViewLoadedCommand #region View EventHandlers protected virtual void OnViewLoadedCommand(RoutedEventArgs e) { EventHandler handler = ViewLoaded; if (handler != null) { handler(this, e); } } #endregion

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  • SIGABRT on any UIView touch

    - by bitcruncher
    Hi. I'm afraid no amount of Googling has been able to save my hyde on this. I seem to be getting SIGABRT error anytime I touch the screen of the phone, on any UIView. The debugger console posts this error before the SIGABRT: .... [310:207] *** -[UIView _exclusiveTouchView]: unrecognized selector sent to instance 0x14c0c0 .... [310:207] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[UIView _exclusiveTouchView]: unrecognized selector sent to instance 0x14c0c0' (this is not my specific call to _exclusiveTouchView, of course.) I would gladly post some code, but the truth is I cannot find (or guess) where this problem may be coming from. This is not happening on any ONE UIView but on all the UIViews in my stack. I can summarize the display logic, though, perhaps that will shed some light. So the application is created and a UIWindow is alloc'd. A single viewcontroller is then alloc'd, which makes and adds its own blank self.view, to which the other UIViews, representing the different game states, are attached. Interestingly enough, this error is does NOT happen on the Simulator, but happens consistently on the device. And I should also mention that the application has yet to override/use any of the touchesBegan:/Ended:/Moved: etc... In other words, this error happens without these methods in the code. I'm really not understanding where this error is coming from... Any suggestions?

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  • Best practice - When to evaluate conditionals of function execution

    - by Tesserex
    If I have a function called from a few places, and it requires some condition to be met for anything it does to execute, where should that condition be checked? In my case, it's for drawing - if the mouse button is held down, then execute the drawing logic (this is being done in the mouse movement handler for when you drag.) Option one says put it in the function so that it's guaranteed to be checked. Abstracted, if you will. public function Foo() { DoThing(); } private function DoThing() { if (!condition) return; // do stuff } The problem I have with this is that when reading the code of Foo, which may be far away from DoThing, it looks like a bug. The first thought is that the condition isn't being checked. Option two, then, is to check before calling. public function Foo() { if (condition) DoThing(); } This reads better, but now you have to worry about checking from everywhere you call it. Option three is to rename the function to be more descriptive. public function Foo() { DoThingOnlyIfCondition(); } private function DoThingOnlyIfCondition() { if (!condition) return; // do stuff } Is this the "correct" solution? Or is this going a bit too far? I feel like if everything were like this function names would start to duplicate their code. About this being subjective: of course it is, and there may not be a right answer, but I think it's still perfectly at home here. Getting advice from better programmers than I is the second best way to learn. Subjective questions are exactly the kind of thing Google can't answer.

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  • Getting Started with Ruby & Ruby on Rails

    - by JakeTheSnake
    Some background: I'm a jack-of-all traits, one of which is programming. I learned VB6 through Excel and PHP for creating websites and so far it's worked out just fine for me. I'm not CS major or even mathematically inclined - logic is what interests me. Current status: I'm willing to learn new and more powerful languages; my first foray into such a route is learning Ruby. I went to the main Ruby website and did the interactive intro. (by the way, I'm currently getting redirected to google.com when I try the link...it's happening to other websites as well...is my computer infected?) I liked what I learned and wanted to get started using Ruby to create websites. I downloaded InstantRails and installed it; everything so far has been fine - the program starts up just fine, and I can test some Ruby code in the console. However my troubles begin when I try and view a web page with Ruby code present. Lastly, my problem: As in PHP, I can browse to the .php file directly and through using PHP tags and some simple 'echo' statements I can be on my way in making dynamic web pages. However with the InstantRails app working, accessing a .rb or .rhtml page doesn't produce similar results. I made a simple text file named 'test.rb' and put basic HTML tags in there (html, head, body) and the Ruby tags <%= and % with some ruby code inside. The web page actually shows the tags and the code - as if it's all just plain HTML. I take it Ruby isn't parsing the page before it is displayed to the user, but this is where my lack of understanding of the Ruby environment stops me short. Where do I go from here?

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  • Open XML document ContentControls problem with signed id's

    - by willvv
    I have an application that generates Open XML documents with Content Controls. To create a new Content Control I use Interop and the method ContentControls.Add. This method returns an instance of the added Content Control. I have some logic that saves the id of the Content Control to reference it later, but in some computers I've been having a weird problem. When I access the ID property of the Content Control I just created, it returns a string with the numeric id, the problem is that when this value is too big, after I save the document, if I look through the document.xml in the generated document, the <w:id/> element of the <w:sdtPr/> element has a negative value, that is the signed equivalent of the value I got from the Id property of the generated control. For example: var contentControl = ContentControls.Add(...); var contentControlId = contentControl.ID; // the value of contentControlId is "3440157266" If I save the document and open it in the Package Explorer, the Id of the Content Control is "-854810030" instead of "3440157266". What have I figured out is this: ((int)uint.Parse("3440157266")).ToString() returns "-854810030" Any idea of why this happens? This issue is hard to replicate because I don't control the Id of the generated controls, the Id is automatically generated by the Interop libraries.

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  • .net real time stream processing - needed huge and fast RAM buffer

    - by mack369
    The application I'm developing communicates with an digital audio device, which is capable of sending 24 different voice streams at the same time. The device is connected via USB, using FTDI device (serial port emulator) and D2XX Drivers (basic COM driver is to slow to handle transfer of 4.5Mbit). Basically the application consist of 3 threads: Main thread - GUI, control, ect. Bus reader - in this thread data is continuously read from the device and saved to a file buffer (there is no logic in this thread) Data interpreter - this thread reads the data from file buffer, converts to samples, does simple sample processing and saves the samples to separate wav files. The reason why I used file buffer is that I wanted to be sure that I won't loose any samples. The application doesn't use recording all the time, so I've chosen this solution because it was safe. The application works fine, except that buffered wave file generator is pretty slow. For 24 parallel records of 1 minute, it takes about 4 minutes to complete the recording. I'm pretty sure that eliminating the use of hard drive in this process will increase the speed much. The second problem is that the file buffer is really heavy for long records and I can't clean this up until the end of data processing (it would slow down the process even more). For RAM buffer I need at lest 1GB to make it work properly. What is the best way to allocate such a big amount of memory in .NET? I'm going to use this memory in 2 threads so a fast synchronization mechanism needed. I'm thinking about a cycle buffer: one big array, the Bus Reader saves the data, the Data Interpreter reads it. What do you think about it? [edit] Now for buffering I'm using classes BinaryReader and BinaryWriter based on a file.

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  • Java swing hold buttons

    - by Simon Charette
    Hi, I'm trying to create a subclass of JButton or AbstractButton that would call specified .actionPerformed as long as the mouse is held down on the button. So far I was thinking of extending JButton, adding a mouse listener on creation (inside constructor) and calling actionPerformed while the mouse is down. So far i came up with that but I was wondwering if I was on the right track and if so, how to correctly implement the "held down" logic. package components; import java.awt.event.ActionEvent; import java.awt.event.MouseEvent; import java.awt.event.MouseListener; import javax.swing.Action; import javax.swing.Icon; import javax.swing.JButton; public class HoldButton extends JButton { private class HeldDownMouseListener implements MouseListener { private boolean mouseIsHeldDown; private HoldButton button; private long millis; public HeldDownMouseListener(HoldButton button, long millis) { this.button = button; this.millis = millis; } @Override public void mouseClicked(MouseEvent arg0) { } @Override public void mouseEntered(MouseEvent arg0) { } @Override public void mouseExited(MouseEvent arg0) { } @Override public void mousePressed(MouseEvent arg0) { mouseIsHeldDown = true; // This should be run in a sub thread? // while (mouseIsHeldDown) { // button.fireActionPerformed(new ActionEvent(button, ActionEvent.ACTION_PERFORMED, "heldDown")); // try { // Thread.sleep(millis); // } catch (InterruptedException e) { // e.printStackTrace(); // continue; // } // } } @Override public void mouseReleased(MouseEvent arg0) { mouseIsHeldDown = false; } } public HoldButton() { addHeldDownMouseListener(); } public HoldButton(Icon icon) { super(icon); addHeldDownMouseListener(); } public HoldButton(String text) { super(text); addHeldDownMouseListener(); } public HoldButton(Action a) { super(a); addHeldDownMouseListener(); } private void addHeldDownMouseListener() { addMouseListener(new HeldDownMouseListener(this, 300)); } } Thanks a lot for your time.

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  • Getting my foot in the SCADA door, how?

    - by bibby
    I keep hearing that I should learn SCADA and its PLC language to upgrade my career. While I enjoy currently being a web and mobile development privateer, the prospects of working for a municipality or industrial entity has its appeals (since I am trying to grow a family). Over the years, I've tought myself to skillfully use php, javascript, java, perl, awk, bash. Surely, these language skills can tranfer somewhat to SCADA's logic controller language. Without any formal training in CS (music major!) other than at the workplace, I wouldn't have been able to pick up those languages and run with them had it not been for their open documentation and free-to-install or already-installed interpreters/compilers. I can't see that this is true with SCADA, and I'm hoping that I'm wrong. Ideally, I'd like to be able to apply for a job that requires [A,B,C] and suggest that they hire me because I already know [A & B]; that they wouldn't have to do a ground-up training with someone that's never programmed before. So, finally, the question; How do I "learn" SCADA? Are there sites and docs? What's going to help me get my foot in the door? Any insight is appreciated. Thanks!

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  • convincing C# compiler that execution will stop after a member returns

    - by Sarah Vessels
    I don't think this is currently possible or if it's even a good idea, but it's something I was thinking about just now. I use MSTest for unit testing my C# project. In one of my tests, I do the following: MyClass instance; try { instance = getValue(); } catch (MyException ex) { Assert.Fail("Caught MyException"); } instance.doStuff(); // Use of unassigned local variable 'instance' To make this code compile, I have to assign a value to instance either at its declaration or in the catch block. However, Assert.Fail will never, to the best of my knowledge, allow execution to proceed past it, hence instance will never be used without a value. Why is it then that I must assign a value to it? If I change the Assert.Fail to something like throw ex, the code compiles fine, I assume because it knows that exception will disallow execution to proceed to a point where instance would be used uninitialized. So is it a case of runtime versus compile-time knowledge about where execution will be allowed to proceed? Would it ever be reasonable for C# to have some way of saying that a member, in this case Assert.Fail, will never allow execution after it returns? Maybe that could be in the form of a method attribute. Would this be useful or an unnecessary complexity for the compiler?

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  • Method return type

    - by sarah xia
    Hi, In my company, a system is designed to have 3 layers. Layer1 is responsible for business logic handling. Layer3 is calling back end systems. Layer2 sits between the two layers so that layer1 doesn't need to know about the back end systems. To replay information from layer3, layer2 needs to define interface to layer1. For example, layer1 wants to check if a PIN from user is correct. It calls layer2 checkPin() method and then layer2 calls the relevant back end system. The checkPin() results could be: correctPin, inCorrectPin and internalError. At the moment, we defined the return type 'int'. So if layer2 returns 0, it means correctPin; if 1 is returned, it means inCorrectPin; if 9 is returned it means internalError. It works. However I feel a bit uneasy about this approach. Are there better ways to do it? For example define an enum CheckPinResult{CORRECT_PIN,INCORRECT_PIN,INTERNAL_ERROR}, and return CheckPinResult type? Thanks, Sarah

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  • web design question (php/ajax)

    - by tom smith
    Hi guys... Hope this isn't a waste of your time. I'm working on a project, and it occured to me that there's a chunk of code out there, that should allow me to see how others have implemented this. I've got a project where I'm going to have a page, with a sel box. the user will select an item from the selList, and based on the item selected, a separate section of the page (areaB) will change in terms of the content/tbls being displayed. i then want to allow the user to go through a series of subpages in areaB, where the user goes through a submit/cancel/confirm process, where the stuff in areaB changes, with the rest of the page remaining the same... i'm trying to figure out the best approach to implement the on both client/server side. i could just have an ugly "if block" where i have abunch of logic, and i completely regen the page each time the user selects an action.. i could have an approach that might involve divs/frames, where i then just regen the targeted frame/div area.. is this even possible?? i could have some form of ajaxy process, which would only alter the targeted section(s) of the page... so.. i'm trying to talk to anyone who has ideas on how to do this, or more ideally, if you know of a good code (client/server) side example of this... that i can examine. i'd really appreciate it!! i've got a more detailed overview but didn't know if it would be cool to post it here... thanks.. tom

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  • Custom webserver caching

    - by Mark Kinsella
    I'm working with a custom webserver on an embedded system and having some problems correctly setting my HTTP Headers for caching. Our webserver is generating all dynamic content as XML and we're using semi-static XSL files to display it with some dynamic JSON requests thrown in for good measure along with semi-static images. I say "semi-static" because the problems occur when we need to do a firmware update which might change the XSL and image files. Here's what needs to be done: cache the XSL and image files and do not cache the XML and JSON responses. I have full control over the HTTP response and am currently: Using ETags with the XSL and image files, using the modified time and size to generate the ETag Setting Cache-Control: no-cache on the XML and JSON responses As I said, everything works dandy until a firmware update when the XSL and image files are sometimes cached. I've seen it work fine with the latest versions of Firefox and Safari but have had some problems with IE. I know one solution to this problem would be simply rename the XSL and image files after each version (eg. logo-v1.1.png, logo-v1.2.png) and set the Expires header to a date in the future but this would be difficult with the XSL files and I'd like to avoid this. Note: There is a clock on the unit but requires the user to set it and might not be 100% reliable which is what might be causing my caching issues when using ETags. What's the best practice that I should employ? I'd like to avoid as many webserver requests as possible but invalidating old XSL and image files after a software update is the #1 priority.

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  • java - codesprint2 programming contest answer

    - by arya
    I recently took part in Codesprint2. I was unable to submit the solution to the following question. http://www.spoj.pl/problems/COINTOSS/ ( I have posted the link to the problem statement at spoj because the codesprint link requires login ) I checked out one of the successful solutions, ( url : http://pastebin.com/uQhNh9Rc ) and the logic used is exactly the same as mine, yet I am still getting "Wrong Answer" I would be very thankful if someone could please tell me what error I have made, as I am unable to find it. Thank you. My code : import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.text.DecimalFormat; import java.util.StringTokenizer; public class Solution { static double solve( int n, int m ) { if( m==n ) return 0; if( m==0 ) return ( Math.pow( 2, n+1 ) - 2 ); else { double res = 1 + ( Double )( solve( n, m+1 ) + solve( n, 0 ))/2; return res; } } public static void main( String[] args ) throws IOException { BufferedReader br = new BufferedReader( new InputStreamReader( System.in )); int n, m; int t = Integer.parseInt( br.readLine() ); StringTokenizer tok; String s; for( int T=0; T<t; T++ ) { s = br.readLine(); tok = new StringTokenizer( s ); n = Integer.parseInt( tok.nextToken() ); m = Integer.parseInt( tok.nextToken() ); DecimalFormat df = new DecimalFormat(); df.setMaximumFractionDigits(2); df.setMinimumFractionDigits(2); System.out.println( df.format ( solve( n, m ) )); } } }

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  • C# TcpClient, getting back the entire response from a telnet device

    - by Dan Bailiff
    I'm writing a configuration tool for a device that can communicate via telnet. The tool sends a command via TcpClient.GetStream().Write(...), and then checks for the device response via TcpClient.GetStream().ReadByte(). This works fine in unit tests or when I'm stepping through code slowly. If I run the config tool such that it performs multiple commands consecutively, then the behavior of the read is inconsistent. By inconsistent I mean sometimes the data is missing, incomplete or partially garbled. So even though the device performed the operation and responded, my code to check for the response was unreliable. I "fixed" this problem by adding a Thread.Sleep to make sure the read method waits long enough for the device to complete its job and send back the whole response (in this case 1.5 seconds was a safe amount). I feel like this is wrong, blocking everything for a fixed time, and I wonder if there is a better way to get the read method to wait only long enough to get the whole response from the device. private string Read() { if (!tcpClient.Connected) throw (new Exception("Read() failed: Telnet connection not available.")); StringBuilder sb = new StringBuilder(); do { ParseTelnet(ref sb); System.Threading.Thread.Sleep(1500); } while (tcpClient.Available > 0); return sb.ToString(); } private void ParseTelnet(ref StringBuilder sb) { while (tcpClient.Available > 0) { int input = tcpClient.GetStream().ReadByte(); switch (input) { // parse the input // ... do other things in special cases default: sb.Append((char)input); break; } } }

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  • Drupal Views api, add simple argument handler

    - by LanguaFlash
    Background: I have a complex search form that stores the query and it's hash in a cache. Once the cache is set, I redirect to something like /searchresults/e6c86fadc7e4b7a2d068932efc9cc358 where that big long string on the end is the md5 hash of my query. I need to make a new argument for views to know what the hash is good for. The reason for all this hastle is because my original search form is way to complex and has way to many arguments to consider putting them all into the path and expecting to do the filtering with the normal views arguments. Now for my question. I have been reading views 2 documentation but not figuring out how to accomplish this custom argument. It doesn't seem to me like this should be as hard as it seems to me like it must be. Leaving aside any knowledge of the veiws api, it would seem that all I need is a callback function that will take the argument from the path as it's only argument and return a list of node id's to filter to. Can anyone point me to a solution or give me some example code? Thanks for your help! You guys are great. PS. I am pretty sure that my design is the best I can come up with, lets don't get off my question and into cross checking my design logic if we can help it.

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