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• JDBC: Does the connection break if i lose reference to the Connection object?

  - by wretrOvian

  Hi. If i have the following method - public static void C() { Connection con = DriverManager.getConnection(); .... // code return; } and i dont call con.close() , will the connection terminate automatically once the method returns?

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• C++ catch blocks - catch exception by value or reference?

  - by John

  I always catch exceptions by value. e.g try{ ... } catch(CustomException e){ ... } But I came across some code that instead had catch(CustomException &e) instead. Is this a)fine b)wrong c)a grey area?

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• Not Possible to Reference self in a Method Declaration?

  - by phasetwenty

  I wanted to write a method with an argument that defaults to a member variable like so: def method(self, arg1=0, arg2=self.member): Apparently this is not allowed. Should I write it a different way, or perhaps use a value of arg2 to signal when to use a different value?

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• Prevent coersion to a single type in unlist() or c(); passing arguments to wrapper functions

  - by Leo Alekseyev

  Is there a simple way to flatten a list while retaining the original types of list constituents?.. Is there a way to programmatically construct a heterogeneous list?.. For instance, I want to create a simple wrapper for functions like png(filename,width,height) that would take device name, file name, and a list of options. The naive approach would be something like my.wrapper <- function(dev,name,opts) { do.call(dev,c(filename=name,opts)) } or similar code with unlist(list(...)). This doesn't work because opts gets coerced to character, and the resulting call is e.g. png(filename,width="500",height="500"). If there's no straightforward way to create heterogeneous lists like that, is there a standard idiomatic way to splice arguments into functions without naming them explicitly (e.g. do.call(dev,list(filename=name,width=opts["width"]))? -- Edit -- Gavin Simpson answered both questions below in his discussion about constructing wrapper functions. Let me give a summary of the answer to the title question: It is possible to construct a heterogeneous list with c() provided the arguments to c() are lists. To wit: > foo <- c("a","b"); bar <- 1:3 > c(foo,bar) [1] "a" "b" "1" "2" "3" > c(list(foo),list(bar)) [[1]] [1] "a" "b" [[2]] [1] 1 2 3 > c(as.list(foo),as.list(bar)) ## this creates a flattened heterogeneous list [[1]] [1] "a" [[2]] [1] "b" [[3]] [1] 1 [[4]] [1] 2 [[5]] [1] 3

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• Is it bad OOP practice to have objects reference each other?

  - by lala

  Pardon my noobness. I'm making a game in which several characters have relationships with each other and they need to be able to interact with each other and store some relationship data regarding how they feel about each other. I have an object for each character. Is it bad for each of those character objects to have an array of all the other character objects in order to perform these interactions? Is there a better way to do this?

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• Passing Func<T> to controller constructure when using Unity IoC with MVC, advantages?

  - by user1361315

  I was looking at a sample of how to setup Unity IoC with MVC, and noticed someone who recommended the approach of having the parameters of Func. I believe the advantage is this is kind of like lazy loading the service, if it never gets called it will never get executed and not consume any resources. private readonly Func<IUserService> _userService; public CourseController(Func<IUserService> userService) { this._userService = userService; } Versus a parameter without a Func: private readonly IUserService _userService; public CourseController(IUserService userService) { this._userService = userService; } Can someone explain to me the differences, is it really more effecient?

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• I am passing a Controller as a parameter, can't get to RedirectToAction method?

  - by Blankman

  My method looks like: public static RedirectToResult(Controller controller, ...) { } when I do: controller. I don't see RedirectToAction, how come?

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• Is there a posibility to break on every object reference in eclipse debugger ?

  - by lbownik

  Suppose I have a class public classs MyClass { private Set<String> set = new HashSet<String>(); //and many methods here } is there a possibility to make an eclipse debugger stop at every line where set member is used ?

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• Where can I find a reference which controls are in which version of MFC?

  - by John

  Preferably with visual illustrations... MSDN just lists class-names and what I really want to see is which versions of MFC have nice modern functionality like dockable toobars, collapsible windows, and other graphical niceties. Does such a 'visual catalog' exist? From MSDN it's not always clear even what each class does without a pretty picture.

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• Why is the new Tuple type in .Net 4.0 a reference type (class) and not a value type (struct)

  - by Bent Rasmussen

  Does anyone know the answer and/or have an oppinion about it? Since tuples would normally not be very large I would assume it would make more sense to use structs than classes for these. What say you?

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• Is it possible to use a string variable to reference an element in Javascript?

  - by somerandomguy

  Here's the quick version of the code as it stands right now: function foo(attributeName, someJSObj, key, newValue) { someJSObj[key].attributeName = newValue; } Obviously this doesn't work, since it just creates a new element called attributeName. Is there an easy way to dereference the attributeName into the string that represents some existing attribute on someJSObj?

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• VB .NET Passing a Structure containing an array of String and an array of Integer into a C++ DLL

  - by DanJunior

  Hi everyone, I'm having problems with marshalling in VB .NET to C++, here's the code : In the C++ DLL : struct APP_PARAM { int numData; LPCSTR *text; int *values; }; int App::StartApp(APP_PARAM params) { for (int i = 0; i < numLines; i++) { OutputDebugString(params.text[i]); } } In VB .NET : <StructLayoutAttribute(LayoutKind.Sequential)> _ Public Structure APP_PARAM Public numData As Integer Public text As System.IntPtr Public values As System.IntPtr End Structure Declare Function StartApp Lib "AppSupport.dll" (ByVal params As APP_PARAM) As Integer Sub Main() Dim params As APP_PARAM params.numData = 3 Dim text As String() = {"A", "B", "C"} Dim textHandle As GCHandle = GCHandle.Alloc(text) params.text = GCHandle.ToIntPtr(textHandle) Dim values As Integer() = {10, 20, 30} Dim valuesHandle As GCHandle = GCHandle.Alloc(values) params.values = GCHandle.ToIntPtr(heightHandle) StartApp(params) textHandle.Free() valuesHandle.Free() End Sub I checked the C++ side, the output from the OutputDebugString is garbage, the text array contains random characters. What is the correct way to do this?? Thanks a lot...

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• A file is being http posted, how can I reference the parameter by index?

  - by Blankman

  An XML file is being posted to a url that my spring mvc is responding to. In .NET, I could do this: request.Form[0] request.Form["abc"] or request.QueryString[0] request.QueryString["some_key"] Now with spring/servlets it seems I can only do this: request.getParameter("some_key") or get all the names or values. When someone is posting a file to a url, using http post, won't this be just a single request parameter then? Can I get the parameter using index with servlets?

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• what is the diffence between call by reference and call by name? [closed]

  - by Dharmendra

  be careful to answer

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• Is there a way to get a reference to all the paragraphs or headings in a web page in JavaScript?

  - by mattbd

  I'm writing a simple Greasemonkey script to strip out all the images, headings and paragraphs from a web page (it's because someone wants to use images of several popular websites with the images and text removed in a presentation about branding of websites). I've figured out how to do so with images by using a for loop and the document.images array like this: var i = 0; var imglngth = document.images.length; for(i=0;i<imglngth;i++) { document.images[i].style.display="none"; } However, I don't believe there's an object representing paragraphs or headers. Any suggestions as to how I could implement this?

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• How to do a back-reference on Google AppEngine?

  - by jCuga

  I'm trying to access an object that is linked to by a db.ReferenceProperty in Google app engine. Here's the model's code: class InquiryQuestion(db.Model): inquiry_ref = db.ReferenceProperty(reference_class=GiftInquiry, required=True, collection_name="inquiry_ref") And I am trying to access it in the following way: linkedObject = question.inquiry_ref and then linkedKey = linkedObject.key but it's not working. Can anyone please help?

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• C++ can local class reference be passed to a function?

  - by aaa

  hi I would like to know if the following is allowed: template < class C > void function(C&); void function() { class {} local; function(local); } thanks

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• how to I get the class name when I am passing in a genertic in my method?

  - by Blankman

  My method looks like: public string DoObjectProperties<T>(T obj, string text) { } Now from within the method, I need to get the string value of the class name that i pass into the method's 'obj' parameter. So if I pass in the User object, I need the text 'user'. To get the properties I am using: typeof(T).GetProperties() How can I get the classes name?

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• Passing arguments to javascript file, how does it work?

  - by vietean

  From the tutorial ScriptJSONOptions of FirebugLite page, I found the below: Script JSON options It is possible to set options using a JSON object inside the linked script: <script type="text/javascript" src="https://getfirebug.com/firebug-lite.js"> { overrideConsole: false, startInNewWindow: true, startOpened: true, enableTrace: true } </script> It means that we can pass the arguments to javascript file. But I don't know how does it work? Update: My question is how to get the arguments inside the js file? P/S: I also looked into code, but I could not find the code is implemented this feature.

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• How to get a reference to the current window?

  - by mystify

  Need a ref to the window in which a view is inside (no matter how deep inside). Usually there is only one window in an iPhone app. How would I access that the most easy way? Is there something cooler than getting the app delegate to access the window?

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• Why does the compiler give an ambiguous invocation error when passing inherited types?

  - by Matt Mitchell

  What is happening in the C# compiler to cause the following ambiguous invocation compilation error? The same issue applies to extension methods, or when TestClass is generic and using instance rather than static methods. class Type1 { } class Type2 : Type1 {} class TestClass { public static void Do<T>(T something, object o) where T : Type1 {} public static void Do(Type1 something, string o) {} } void Main() { var firstInstance = new Type1(); TestClass.Do(firstInstance, new object()); // Calls Do(Type1, obj) TestClass.Do(firstInstance, "Test"); // Calls Do<T>(T, string) var secondInstance = new Type2(); TestClass.Do(secondInstance, new object()); // Calls Do(Type1, obj) TestClass.Do(secondInstance, "Test"); // "The call is ambiguous" compile error }

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• stl string return by const reference vs. const char*

  - by user342673

  i have a STL string member variable in my class, class A { public: const char* getData1() const { return data.c_str()); const string& getData2() const { return _data; } private: string _data; }; getData1() vs. getData2(), which one is better?

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• MySQL datetime fields and daylight savings time -- how do I reference the "extra" hour?

  - by Aaron

  I'm using the America/New York timezone. In the Fall we "fall back" an hour -- effectively "gaining" one hour at 2am. At the transition point the following happens: it's 01:59:00 -04:00 then 1 minute later it becomes: 01:00:00 -05:00 So if you simply say "1:30am" it's ambiguous as to whether or not you're referring to the first time 1:30 rolls around or the second. I'm trying to save scheduling data to a MySQL database and can't determine how to save the times properly. Here's the problem: "2009-11-01 00:30:00" is stored internally as 2009-11-01 00:30:00 -04:00 "2009-11-01 01:30:00" is stored internally as 2009-11-01 01:30:00 -05:00 This is fine and fairly expected. But how do I save anything to 01:30:00 -04:00? The documentation does not show any support for specifying the offset and, accordingly, when I've tried specifying the offset it's been duly ignored. The only solutions I've thought of involve setting the server to a timezone that doesn't use daylight savings time and doing the necessary transformations in my scripts (I'm using PHP for this). But that doesn't seem like it should be necessary. Many thanks for any suggestions.

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• Reference properteries declared in a protocol and implemented in the anonymous category?

  - by Heath Borders

  I have the following protocol: @protocol MyProtocol @property (nonatomic, retain) NSObject *myProtocolProperty; -(void) myProtocolMethod; @end and I have the following class: @interface MyClass : NSObject { } @end I have a class extension declared, I have to redeclare my protocol properties here or else I can't implement them with the rest of my class. @interface()<MyProtocol> @property (nonatomic, retain) NSObject *myExtensionProperty; /* * This redeclaration is required or my @synthesize myProtocolProperty fails */ @property (nonatomic, retain) NSObject *myProtocolProperty; - (void) myExtensionMethod; @end @implementation MyClass @synthesize myProtocolProperty = _myProtocolProperty; @synthesize myExtensionProperty = _myExtensionProperty; - (void) myProtocolMethod { } - (void) myExtensionMethod { } @end In a consumer method, I can call my protocol methods and properties just fine. Calling my extension methods and properties produces a warning and an error respectively. - (void) consumeMyClassWithMyProtocol: (MyClass<MyProtocol> *) myClassWithMyProtocol { myClassWithMyProtocol.myProtocolProperty; // works, yay! [myClassWithMyProtocol myProtocolMethod]; // works, yay! myClassWithMyProtocol.myExtensionProperty; // compiler error, yay! [myClassWithMyProtocol myExtensionMethod]; // compiler warning, yay! } Is there any way I can avoid redeclaring the properties in MyProtocol within my class extension in order to implement MyProtocol privately?

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• Is it good practice to pass scoped_ptr by reference (from one method to another inside a class)?

  - by eriks

  Or if i need to do that, than i should just use shared_ptr? I know i have many questions regarding smart pointer - i still don't quite understand when to use which smart pointer.

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