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• correct technical term for this pattern

  - by Oliver A.

  sometimes I use a pattern which is very similar to the singleton pattern: There is one default instance which and a static get method to aces it. But you may create other instances and pass it as optional parameter and if you want to and you can even replace the default instance with a instance from a child class. So it is NO SINGLETON at all but it is used like one singleton in most cases. Anyone got an idea who to call something like this ? Maybe half*** singleton? domiton?

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• Extending appengine's db.Property with caching

  - by Noio

  I'm looking to implement a property class for appengine, very similar to the existing db.ReferenceProperty. I am implementing my own version because I want some other default return values. My question is, how do I make the property remember its returned value, so that the datastore query is only performed the first time the property is fetched? What I had is below, and it does not work. I read that the Property classes do not belong to the instances, but to the model definition, so I guess that the return value is not cached for each instance, but overwritten on the model every time. Where should I store this _resolved variable? class PageProperty(db.Property): data_type = Page def get_value_for_datastore(self, model_instance): page = super(PageProperty, self).get_value_for_datastore(model_instance) self._resolved = page return page.key().name() def make_value_from_datastore(self, value): if not hasattr(self, '_resolved'): self._resolved = Page.get_by_name(value) return self._resolved

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• Why is the Dependency Property not returning its value?

  - by B-Rad

  I have a MyUserControl with the following Xaml: <TextBox Text="{Binding InputValueProperty}" /> In the MyUserControl.xaml.cs I have: public string InputValue { get { return (string)GetValue(InputValueProperty); } set { SetValue(InputValueProperty, value); } } public static readonly DependencyProperty InputValueProperty = DependencyProperty.Register("InputValueProperty", typeof(string), typeof(MyUserControl)); In my MainWindow.xaml I create a user control: <local:MyUserControl InputValue="My Input" /> Later on in my MainWindow.xaml.cs I am trying to access this string. All instances of MyUserControl are contained in a List and I access them with a foreach. string temp = userControl.InputValue; This is always null. In my MainWindow.xaml I can see the "My Input" in the text box of the user control but I can't ever seem to get it out of there.

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• Correct way to clear/release an array of arrays

  - by iFloh

  And again my array of arrays .... When I have an array "x" that contains multiple instances of an array "y", how do I clear/release it without risking memory leaks? are the following calls sufficient? (a) clearing the array [x removeAllObjects]; (b) releasing the array [x release]; or do I need to enumerate the array, such as: (c) clearing the array for(int i=0;i<x.count;i++) [[x objectAtIndex:i] release]; [x removeAllObjects]; (d) releasing the array for(int i=0;i<x.count;i++) [[x objectAtIndex:i] release]; [x release]; thanks in advance

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• How do you create a generic method in a class?

  - by Seth Spearman

  Hello, I am really trying to follow the DRY principle. I have a sub that looks like this? Private Sub DoSupplyModel OutputLine("ITEM SUMMARIES") Dim ItemSumms As New SupplyModel.ItemSummaries(_currentSupplyModel, _excelRows) ItemSumms.FillRows() OutputLine("") OutputLine("NUMBERED INVENTORIES") Dim numInvs As New SupplyModel.NumberedInventories(_currentSupplyModel, _excelRows) numInvs.FillRows() OutputLine("") End Sub I would like to collapse these into a single method using generics. For the record, ItemSummaries and NumberedInventories are both derived from the same base class DataBuilderBase. I can't figure out the syntax that will allow me to do ItemSumms.FillRows and numInvs.FillRows in the method. FillRows is declared as Public Overridable Sub FillRows in the base class. Thanks in advance. EDIT Here is my end result Private Sub DoSupplyModels() DoSupplyModelType("ITEM SUMMARIES",New DataBlocks(_currentSupplyModel,_excelRows) DoSupplyModelType("DATA BLOCKS",New DataBlocks(_currentSupplyModel,_excelRows) End Sub Private Sub DoSupplyModelType(ByVal outputDescription As String, ByVal type As DataBuilderBase) OutputLine(outputDescription) type.FillRows() OutputLine("") End Sub But to answer my own question...I could have done this... Private Sub DoSupplyModels() DoSupplyModelType(Of Projections)("ITEM SUMMARIES") DoSupplyModelType(Of DataBlocks)("DATA BLOCKS") End Sub Private Sub DoSupplyModelType(Of T as DataBuilderBase)(ByVal outputDescription As String, ByVal type As T) OutputLine(outputDescription) dim type as New T(_currentSupplyModel,_excelRows) type.FillRows() OutputLine("") End Sub Is that right? Does the New T() work? Seth

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• Are static members inherited? (C++)

  - by Keand64

  When static members are inherited, are they static for the entire heirarchy, or just that class, ie: class SomeClass { public: SomeClass(){total++;} static int total; }; class SomeDerivedClass: public SomeClass { public: SomeDerivedClass(){total++;} }; int main() { SomeClass A; SomeClass B; SomeDerivedClass C; return 0; } would total be 3 in all three instances, or would it be 2 for SomeClass and 1 for SomeDerivedClass?

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• Using non-Railsy route to prepopulate a form

  - by user94154

  I have many instances of a Rails model, Post. When viewing an individual post, I'd like to create a form to create a child of Post called Comment. I'd like to prepopulate this form with a hidden tag that contains the post_id which is the foreign key in Comment. The Railsy way to do this is to create a fancy-ish route such as: /comments/new/post/:post_id However, this gunks up the routes file and doesn't leave much flexibility. Let's say I want to create a link somewhere else that prepopulates a different attribute of the form...then I'd have to add another route for this. So I think I'm going to create urls like this on /posts/show/:id: /comments/new?comment[post_id]=<%= @post.id %> This way I can add any other attributes as I need. I know the plus side associated with this, now what are the downsides?

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• Javascript Inheritance and Arrays

  - by Inespe

  Hi all! I am trying to define a javascript class with an array property, and its subclass. The problem is that all instances of the subclass somehow "share" the array property: // class Test function Test() { this.array = []; this.number = 0; } Test.prototype.push = function() { this.array.push('hello'); this.number = 100; } // class Test2 : Test function Test2() { } Test2.prototype = new Test(); var a = new Test2(); a.push(); // push 'hello' into a.array var b = new Test2(); alert(b.number); // b.number is 0 - that's OK alert(b.array); // but b.array is containing 'hello' instead of being empty. why? As you can see I don't have this problem with primitive data types... Any suggestions?

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• iPhone view architecture question

  - by Joe

  So I have (for instance) three views: A: root view B: a view functionally identical to root C: a data entry view which collects a few piece of info What I'm trying to do is reuse C to supply the data it collects to either A or B. It should supply the data to whichever of the two it is pushed onto. The data for A is similar, but functionally distinct, to what collects for B. Right now, I'm passing data from C to A or B via a singleton class. What I'm trying to avoid is having two instances of C, one to supply data to A and B (because, in actuality, the program will have 5 total views like C. Does the question make sense?

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• Updating a database periodically with Java

  - by MSR

  I would like to perform updates to a MySQL database using two separate classes (that do different things) -- one doing so every 10 seconds, and the second every minute. I have a few gaps in my Java knowledge and I'm wondering what the best way to achieve it is. Importantly, if connectivity to the database is lost, I need reconnection attempts to occur indefinitely, and I'm guessing the use of Prepared Statements will make queries more efficient. Should the connection to the database be left open all the time or closed between the updates being run? Maybe I also need to think about clearing objects/resources out of memory if the class instances are going to be run indefinitely.

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• The most efficient way to calculate an integral in a dataset range

  - by Annalisa

  I have an array of 10 rows by 20 columns. Each columns corresponds to a data set that cannot be fitted with any sort of continuous mathematical function (it's a series of numbers derived experimentally). I would like to calculate the integral of each column between row 4 and row 8, then store the obtained result in a new array (20 rows x 1 column). I have tried using different scipy.integrate modules (e.g. quad, trpz,...). The problem is that, from what I understand, scipy.integrate must be applied to functions, and I am not sure how to convert each column of my initial array into a function. As an alternative, I thought of calculating the average of each column between row 4 and row 8, then multiply this number by 4 (i.e. 8-4=4, the x-interval) and then store this into my final 20x1 array. The problem is...ehm...that I don't know how to calculate the average over a given range. The question I am asking are: Which method is more efficient/straightforward? Can integrals be calculated over a data set like the one that I have described? How do I calculate the average over a range of rows?

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• How can I tell what is using the memory when there is a heap overflow in Java?

  - by Grae

  Hi all, I know a little about profiling, but what I am particularlly insterest in, is what has all the memory when I get these heap over flow exceptions. I will start getting them after about a hour of debugging. I am hoping there is some sort of dump or something, that I can use to get a list of what instances are around at the time the program starts. By the way, sorry if this is a lazy question. I really shoud put sometime in learning about profiling. Grae

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• living column in instruments

  - by dubbeat

  In the context of allocations what exactly does the living column mean? Does it mean the number of times an object was created or does it mean how many instances of an object there is? I ask because I'm testing going in and out of a view. When I enter the view I create a class "myClass". When I exit the view I nil "myClass" and release it. If I go in and out of the view 6 times for example the living column in instruments for "myClass" says 6. Is this normal or is it not being released properly?

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• Is there a way to automatically update application on Android?

  - by Levara

  Hi, I'm developing an application that will most likely be preinstalled on devices. It will be also available on Market. Is there a way to update those instances that are not downloaded through Market, since Market won't notify users about an update. I was thinking about, as suggested here, trying to contact my site periodically, and when update is available, download it. I'm wondering if there is a way to do this update automatically, so that user doesn't have to do anything (like running the package manually). Or, when my site shows update is available, to offer users an update through Market, even though it's not installed through Market. Thanks!

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• Compilation failing - no #include - boost

  - by jwoolard

  Hi, I'm trying to compile a third-party library, but g++ is complaining about the following line: typedef boost::shared_ptr<MessageConsumer> MessageConsumerPtr; The strange thing is, there is no #include directive in the file - and it is clearly supposed to be this way; there are about 60 files with the same (or very similar) issues. Clearly if there was an #include directive referencing the relevant boost header this would compile cleanly. My question is: how can I get g++ to somehow automagically find the relevant symbol (in all instances of this issue, it is a namespace that can't be found - usually std:: or boost::) by either automatically processing the relevant header (or some other mechanism). Thanks. Edit My current g++ call looks like: g++ -fPIC -O3 -DUSING_PCH -D_REENTRANT -I/usr/include/boost -I./ -c MessageInterpreter.cpp -o MessageInterpreter.o

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• Mysql SELECT with an OR across 2 columns

  - by Haroldo

  I'm creating a 'similar items' link table. i have a 2 column table. both columns contains product ids. The table is showing that these items are similar. However ids in the left column are more valuable. Say i want to select similar items to product '125b'. i only want 3 similar items to 125b. If there are any instances of 125b in col1 I would prefer these to finding 125b in col2. so i need a select statement along the lines of SELECT * FROM similar_items WHERE col_1={$id} OR col_2={$id} ORDER BY column(?) LIMIT 3 i do not want to do 2 separate queries ( ie query 2 if count(query1) <3 )

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• What is the difference between these two ways of creating NSStrings?

  - by adame

  NSString *myString = @"Hello"; NSString *myString = [NSString stringWithString:@"Hello"]; I understand that using method (1) creates a pointer to a string literal that is defined as static memory (and cannot be deallocated) and that using (2) creates an NSString object that will be autoreleased. Is using method (1) bad? What are the major differences? Is there any instances where you would want to use (1)? Is there a performance difference? P.S. I have searched extensively on Stack Overflow and while there are questions on the same topic, none of them have answers to the questions I have posted above.

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• Accessing primitive properties from objects stored in a NSDictionary

  - by ChrisS

  Apologies if this is a basic question, I am just starting with Objective-C and trying to wrap things around in my head! I have a simple class of the form: @interface Whatever : NSObject { int somePrimitive; SomeObject* someObject; } @property (nonatomic) int somePrimitive; @property (nonatomic, retain) SomeObject* someObject; The class is more involved that this, but this illustrates the purpose. When I store instances of this class in a NSMutableDictionary: Whatever *whatever = [[Whatever alloc] init]; whatever.somePrimitive = 1; whatever.someObject = ...; [myDictionary setObject:whatever forKey:@"someKey"]; and then try to retrieve the object later: Whatever *result = [myDictionary valueForKey:@"someKey"]; then, result.someObject is ok to reference but, result.somePrimitive crashes. Does the NSDictionary not copy over the primitives of the object? Is the rule that the object stored in a dictionary should only contain objects?

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• Methods specific only to an instance? What are they called in Ruby?

  - by daremarkovic

  I know there are "instance methods", "class methods" but what are these types of methods called, for eg: s1 = "This is my STRING!" def s1.m1 downcase end p s1 # => "This is my STRING!" p s1.m1 # => "this is my string!" What type of method is the "m1" method called on the s1 "instance" of the "string" class? It's really weird because I didn't know this was possible at all if I try: s2 = "This is ANOTHER string" s2.m1 # => Won't work! Which kind of makes sense, but not sure why defining methods like m1 on instances on a class are useful at all.

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• Is MSDN referencing a system.thread, a worker thread, an io thread or all three?

  - by w0051977

  Please see the warning below taken from the StreamWriter class specification (http://msdn.microsoft.com/en-us/library/system.io.streamwriter.aspx): "Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe." I understand that a W3WC process contains two thread pools i.e. worker threads and I/O threads. A worker thread could contain many threads of its own (if the application creates its own System.Thread instances). Does the warning only relate to System.Threads or does it relate to worker threads and I/O threads as well I.e. as the instance variables of the streamwriter class are not thread safe then does this mean that there would be problems if multiple worker threads access it eg if two users on two different web clients attempt to write to the log file at the same time, then could one lock out the other?

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• How do I specify a dynamic position for the start of substring?

  - by analyticsPierce

  As in the example, I am trying to substring the Video_full column in a data.frame (video_data_2) I am working on. I want to keep all the characters after the period. The period is always present, there is only one period and it is in a different position in each value for the column. Date Video_full Instances 1 Apr 1, 2010 installs/AA.intro_video_1 546 2 Apr 1, 2010 installs/ABAC.intro_video_2 548 I got substring to work; video_data_2$Video_full <- substring(video_data_2$Video_full,11) And strsplit also; strsplit("installs/AA.intro_video_1 ",'[.]') I'm just not able to figure out how to start the substring in a dynamic position or only keep the second value returned by strsplit. Thanks for any help you can offer for a simple question.

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• How to customize file dialog in wpf

  - by ManjuAnoop

  In Windows7 I am using a customized Open File Dialog( WPF application). My Open File dialog is derived from Microsoft.Win32.CommonDialog. The dialog have old look, how to change this to new look (windows7 file dialog look(Explorer style)). Code portion: private const int OFN_ENABLESIZING = 0x00800000; private const int OFN_EXPLORER = 0x00080000; private const int OFN_ENABLEHOOK = 0x00000020; protected override bool RunDialog(IntPtr hwndOwner) { OPENFILENAME_I.WndProc proc = new OPENFILENAME_I.WndProc(this.HookProc); OPENFILENAME_I ofn = new OPENFILENAME_I(); this._charBuffer = CharBuffer.CreateBuffer(0x2000); if (this._fileNames != null) { this._charBuffer.PutString(this._fileNames[0]); } ofn.lStructSize = Marshal.SizeOf(typeof(OPENFILENAME_I)); ofn.hwndOwner = hwndOwner; ofn.hInstance = IntPtr.Zero; ofn.lpstrFilter = MakeFilterString(this._filter, this.DereferenceLinks); ofn.nFilterIndex = this._filterIndex; ofn.lpstrFile = this._charBuffer.AllocCoTaskMem(); ofn.nMaxFile = this._charBuffer.Length; ofn.lpstrInitialDir = this._initialDirectory; ofn.lpstrTitle = this._title; ofn.Flags = OFN_EXPLORER | OFN_ENABLESIZING | OFN_ENABLEHOOK; ofn.lpfnHook = proc; ofn.FlagsEx = 0x1000000 ; NativeMethods.GetOpenFileName(ofn); // } [SecurityCritical, SuppressUnmanagedCodeSecurity, DllImport("comdlg32.dll", CharSet = CharSet.Unicode, SetLastError = true)] internal static extern bool GetOpenFileName([In, Out] OPENFILENAME_I ofn);

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• Finding records within a 5 min time interval in SQL

  - by Mellonjollie

  I have a table with over 100,000 rows that contain the following columns: ID, Time, and Boolean. The time column tracks time down to the second. I need a query that will find all instances of Boolean = 1 for every 5 minute interval of time from the start of the table to the end, then group the count by time interval. The table represents 4 hours of data, so I should get 48 rows of results. I'm using MS SQL Server. I've tried a few approaches, but the time interval logic is giving me a hard time.

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• Sharepoint always down on the weekend?

  - by TheGambler

  For some reason, our sharepoint site always goes down on Saturday. It's the stangest thing and I can't figure out why. I'm a total noob at sharepoint and have been thrown into being the go to guy for sharepoint with my current employer. I've tried bouncing IIS on Fridays to see if there is anything I can do before hand. Is there anything that might be scheduled that I may not know about that would cause sharepoint to go down? Remember I'm a total noob as sharepoint. Thanks to all that reply. Edit: Also this our front-end and database instances are on virtual servers.

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• Python to C# Conversion of RGBA values not working

  - by clangers

  I'm currently converting some python code to C#, and I'm having an issue with the RGBA C# libraries # Original Python Code: d = math.sqrt( (x - size/2.0)**2 + (y - size/2.0)**2 ) rgbVal = int(200*d/md + 50) rgba = (0,0,0, 255 - rgbVal) img.putpixel((x,y), rgba) // My C# Code double d = Math.Sqrt(Math.Pow((x - DotSize / 2.0), 2) + Math.Pow((y - DotSize / 2.0), 2)); int rgbVal = (int) (200 * d / md + 50); Color color = Color.FromArgb(255 - rgbVal, 0, 0, 0); // ** ERROR ** img.SetPixel(x,y, color); At both instances of the code d is equal to 106 and md is equal to 53. However the resulting rgbVal value is 450. This would obviously mean that 255 - 450 is -195, which causes an error to be thrown as each individual value must be between 0 and 255. Anyone have any idea how I can fix this. Please note that the data is the same when running both the python and C# versions.

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