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  • Returning a struct from a class method

    - by tree
    I have a header file that looks something like the following: class Model { private: struct coord { int x; int y; } xy; public: .... coord get() const { return xy; } }; And in yet another file (assume ModelObject exists): struct c { int x; int y; void operator = (c &rhs) { x = rhs.x; y = rhs.y; }; } xy; xy = ModelObject->get(); The compiler throws an error that says there is no known covnersion from coord to c. I believe it is because it doesn't know about coord type because it is declared inside of a class header. I can get around that by declaring the struct outside of the class, but I was wondering if it is possible to do the way I am, or is this generally considered bad practice

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  • Overloading *(iterator + n) and *(n + iterator) in a C++ iterator class?

    - by exscape
    (Note: I'm writing this project for learning only; comments about it being redundant are... uh, redundant. ;) I'm trying to implement a random access iterator, but I've found very little literature on the subject, so I'm going by trial and error combined with Wikpedias list of operator overload prototypes. It's worked well enough so far, but I've hit a snag. Code such as exscape::string::iterator i = string_instance.begin(); std::cout << *i << std::endl; works, and prints the first character of the string. However, *(i + 1) doesn't work, and neither does *(1 + i). My full implementation would obviously be a bit too much, but here's the gist of it: namespace exscape { class string { friend class iterator; ... public: class iterator : public std::iterator<std::random_access_iterator_tag, char> { ... char &operator*(void) { return *p; // After some bounds checking } char *operator->(void) { return p; } char &operator[](const int offset) { return *(p + offset); // After some bounds checking } iterator &operator+=(const int offset) { p += offset; return *this; } const iterator operator+(const int offset) { iterator out (*this); out += offset; return out; } }; }; } int main() { exscape::string s = "ABCDEF"; exscape::string::iterator i = s.begin(); std::cout << *(i + 2) << std::endl; } The above fails with (line 632 is, of course, the *(i + 2) line): string.cpp: In function ‘int main()’: string.cpp:632: error: no match for ‘operator*’ in ‘*exscape::string::iterator::operator+(int)(2)’ string.cpp:105: note: candidates are: char& exscape::string::iterator::operator*() *(2 + i) fails with: string.cpp: In function ‘int main()’: string.cpp:632: error: no match for ‘operator+’ in ‘2 + i’ string.cpp:434: note: candidates are: exscape::string exscape::operator+(const char*, const exscape::string&) My guess is that I need to do some more overloading, but I'm not sure what operator I'm missing.

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  • How do I go about overloading C++ operators to allow for chaining?

    - by fneep
    I, like so many programmers before me, am tearing my hair out writing the right-of-passage-matrix-class-in-C++. I have never done very serious operator overloading and this is causing issues. Essentially, by stepping through This is what I call to cause the problems. cMatrix Kev = CT::cMatrix::GetUnitMatrix(4, true); Kev *= 4.0f; cMatrix Baz = Kev; Kev = Kev+Baz; //HERE! What seems to be happening according to the debugger is that Kev and Baz are added but then the value is lost and when it comes to reassigning to Kev, the memory is just its default dodgy values. How do I overload my operators to allow for this statement? My (stripped down) code is below. //header class cMatrix { private: float* _internal; UInt32 _r; UInt32 _c; bool _zeroindexed; //fast, assumes zero index, no safety checks float cMatrix::_getelement(UInt32 r, UInt32 c) { return _internal[(r*this->_c)+c]; } void cMatrix::_setelement(UInt32 r, UInt32 c, float Value) { _internal[(r*this->_c)+c] = Value; } public: cMatrix(UInt32 r, UInt32 c, bool IsZeroIndexed); cMatrix( cMatrix& m); ~cMatrix(void); //operators cMatrix& operator + (cMatrix m); cMatrix& operator += (cMatrix m); cMatrix& operator = (const cMatrix &m); }; //stripped source file cMatrix::cMatrix(cMatrix& m) { _r = m._r; _c = m._c; _zeroindexed = m._zeroindexed; _internal = new float[_r*_c]; UInt32 size = GetElementCount(); for (UInt32 i = 0; i < size; i++) { _internal[i] = m._internal[i]; } } cMatrix::~cMatrix(void) { delete[] _internal; } cMatrix& cMatrix::operator+(cMatrix m) { return cMatrix(*this) += m; } cMatrix& cMatrix::operator*(float f) { return cMatrix(*this) *= f; } cMatrix& cMatrix::operator*=(float f) { UInt32 size = GetElementCount(); for (UInt32 i = 0; i < size; i++) { _internal[i] *= f; } return *this; } cMatrix& cMatrix::operator+=(cMatrix m) { if (_c != m._c || _r != m._r) { throw new cCTException("Cannot add two matrix classes of different sizes."); } if (!(_zeroindexed && m._zeroindexed)) { throw new cCTException("Zero-Indexed mismatch."); } for (UInt32 row = 0; row < _r; row++) { for (UInt32 column = 0; column < _c; column++) { float Current = _getelement(row, column) + m._getelement(row, column); _setelement(row, column, Current); } } return *this; } cMatrix& cMatrix::operator=(const cMatrix &m) { if (this != &m) { _r = m._r; _c = m._c; _zeroindexed = m._zeroindexed; delete[] _internal; _internal = new float[_r*_c]; UInt32 size = GetElementCount(); for (UInt32 i = 0; i < size; i++) { _internal[i] = m._internal[i]; } } return *this; }

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  • Overloading interface buttons, what are the best practices?

    - by XMLforDummies
    Imagine you'll have always a button labeled "Continue" in the same position in your app's GUI. Would you rather make a single button instance that takes different actions depending on the current state? private State currentState = State.Step1; private ContinueButton_Click() { switch(currentState) { case State.Step1: DoThis(); currentState = State.Step2; break; case State.Step2: DoThat(); break; } } Or would you rather have something like this? public Form() { this.ContinueStep2Button.Visible = false; } private ContinueStep1Button_Click() { DoThis(); this.ContinueStep1Button.Visible = false; this.ContinueStep2Button.Visible = true; } private ContinueStep2Button_Click() { DoThat(); }

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  • Go - Concurrent method

    - by nevalu
    How to get a concurrent method? In my case, the library would be called from a program to get a value to each argument str --in method Get()--. When it's used Get() then it assigns a variable from type bytes.Buffer which it will have the value to return. The returned values --when it been concurrently called-- will be stored into a database or a file and it doesn't matter that its output been of FIFO way (from method). type test struct { foo uint8 bar uint8 } func NewTest(arg1 string) (*test, os.Error) {...} func (self *test) Get(str string) ([]byte, os.Error) { var format bytes.Buffer ... } I think that all code inner of method Get() should be put inner of go func() {...}(), and then to use a channel. Would there be a problem if it's called another method from Get()? Or would it also has to be concurrent?

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  • Overloading Console.ReadLine possible? (or any static class method)

    - by comecme
    I'm trying to create an overload of the System.Console.ReadLine() method that will take a string argument. My intention basically is to be able to write string s = Console.ReadLine("Please enter a number: "); in stead of Console.Write("Please enter a number: "); string s = Console.ReadLine(); I don't think it is possible to overload Console.ReadLine itself, so I tried implementing an inherited class, like this: public static class MyConsole : System.Console { public static string ReadLine(string s) { Write(s); return ReadLine(); } } That doesn't work though, cause it is not possible to inherit from System.Console (because it is a static class which automatically makes is a sealed class). Does it make sense what I'm trying to do here? Or is it never a good idea to want to overload something from a static class?

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  • [PHP] Weird problem with dynamic method invocation

    - by Rolf
    Hi everyone, this time, I'm facing a really weird problem. I've the following code: $xml = simplexml_load_file($this->interception_file); foreach($xml->children() as $class) { $path = str_replace('__CLASS_DIR__',CLASS_DIR,$class['path']); if(!is_file($path)) { throw new Exception('Bad configuration: file '.$path.' not found'); } $className = pathinfo($path,PATHINFO_FILENAME); foreach($class as $method) { $method_name = $method['name']; $obj = new $className(); var_dump(in_array($method_name,get_class_methods($className)));exit; echo $obj->$method_name();### not a method ??? } } As you can see, I get the class name and method name from an XML file. I can create an instance of the class without any problem. The var_dump at the end returns true, that means $method_name (which has 2 optional parameters) is a method of $className. BUT, and I am pretty sure the syntax is correct, when I try: $obj-$method_name() I get: Fatal error: Method name must be a string If you have any ideas, pleaaaaase tell me :) Thanks in advance, Rolf

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  • When using method chaining, do I reuse the object or create one?

    - by MainMa
    When using method chaining like: var car = new Car().OfBrand(Brand.Ford).OfModel(12345).PaintedIn(Color.Silver).Create(); there may be two approaches: Reuse the same object, like this: public Car PaintedIn(Color color) { this.Color = color; return this; } Create a new object of type Car at every step, like this: public Car PaintedIn(Color color) { var car = new Car(this); // Clone the current object. car.Color = color; // Assign the values to the clone, not the original object. return car; } Is the first one wrong or it's rather a personal choice of the developer? I believe that he first approach may quickly cause the intuitive/misleading code. Example: // Create a car with neither color, nor model. var mercedes = new Car().OfBrand(Brand.MercedesBenz).PaintedIn(NeutralColor); // Create several cars based on the neutral car. var yellowCar = mercedes.PaintedIn(Color.Yellow).Create(); var specificModel = mercedes.OfModel(99).Create(); // Would `specificModel` car be yellow or of neutral color? How would you guess that if // `yellowCar` were in a separate method called somewhere else in code? Any thoughts?

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  • in python: can i pass class method as and a default argument to another class method

    - by alex
    i want to to pass class method as and a default argument to another class method, so that i can re-use the method as a @classmethod @classmethod class foo: def func1(self,x): do somthing; def func2(self, aFunc = self.func1): # make some a call to afunc afunc(4) this why when the method func2 is called within the class aFunc defaults to self.func1, but i can call this same function from outside of the class and pass it a different function at the input. i get NameError: name 'self' is not defined

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  • How to name a static factory method in the utility class?

    - by leventov
    I have an interface MyLongNameInterface with a counterpart utility class MyLongNameInterfaces. What is the best name for a static factory method in the utility class, which creates an instance of MyLongNameInterface? MyLongNameInterfaces.newInstance() -- a new instance of the utility class? MyLongNameInterfaces.newMyLongNameInterface() -- too verbose MyLongNameInterfaces.create() -- create an instance of the utility class? Also, create is not a widely used conventional verb in Java better option?

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  • call a class method from inside an instance method from a module mixin (rails)

    - by sean
    Curious how one would go about calling a class method from inside an instance method of a module which is included by an active record class. For example I want both user and client models to share the nuts and bolts of password encryption. # app/models class User < ActiveRecord::Base include Encrypt end class Client < ActiveRecord::Base include Encrypt end # app/models/shared/encrypt.rb module Encrypt def authenticate # I want to call the ClassMethods#encrypt_password method when @user.authenticate is run self.password_crypted == self.encrypt_password(self.password) end def self.included(base) base.extend ClassMethods end module ClassMethods def encrypt_password(password) Digest::SHA1.hexdigest(password) end end end However, this fails. Says that the class method cannot be found when the instance method calls it. I can call User.encrypt_password('password') but User.new.encrypt_password fails Any thoughts?

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  • Java Finalize method call

    - by Rajesh Kumar J
    I need to find when finalized method called in the JVM. I Created a test Class which write into file when finalized method called by Overriding the protected finalize method It is not executing. Can anybody tell me the reason why it is not executing?? Thanks in Advance

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  • ASP.NET lock thread method

    - by Peter
    Hello, I'm developing an ASP.NET forms webapplication using C#. I have a method which creates a new Order for a customer. It looks similar to this; private string CreateOrder(string userName) { // Fetch current order Order order = FetchOrder(userName); if (order.OrderId == 0) { // Has no order yet, create a new one order.OrderNumber = Utility.GenerateOrderNumber(); order.Save(); } return order; } The problem here is, it is possible that 1 customer in two requests (threads) could cause this method to be called twice while another thread is also inside this method. This can cause two orders to be created. How can I properly lock this method, so it can only be executed by one thread at a time per customer? I tried; Mutex mutex = null; private string CreateOrder(string userName) { if (mutex == null) { mutex = new Mutex(true, userName); } mutex.WaitOne(); // Code from above mutex.ReleaseMutex(); mutex = null; return order; } This works, but on some occasions it hangs on WaitOne and I don't know why. Is there an error, or should I use another method to lock? Thanks

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  • custom compare method in objective c

    - by Jonathan
    I'm trying to use a custom compare method (for use with sortedArrayusingSelector) and on another website I got that the format is: -(NSComparisonResult) orderByName:(id)otherobject { That's all bery well and good except how do I compare the otherObject to anything as there's only one thing passed to the method? Like how does the NSString method of compare: compare 2 strings when only one string is passed?

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  • groovy call private method in Java super class

    - by Jeff Storey
    I have an abstract Java class MyAbstractClass with a private method. There is a concrete implementation MyConcreteClass. public class MyAbstractClass { private void somePrivateMethod(); } public class MyConcreteClass extends MyAbstractClass { // implementation details } In my groovy test class I have class MyAbstractClassTest { void myTestMethod() { MyAbstractClass mac = new MyConcreteClass() mac.somePrivateMethod() } } I get an error that there is no such method signature for somePrivateMethod. I know groovy can call private methods but I'm guessing the problem is that the private method is in the super class, not MyConcreteClass. Is there a way to invoke a private method in the super class like this (other than using something like PrivateAccessor)? thanks Jeff

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  • Invoke private method with interface as argument

    - by Stephanie
    Hi, I've been attempting to invoke a private method whose argument is a parameter and I can't quite seem to get it right. Here's kind of how the code looks so far: public class TestClass { public TestClass(){ } private void simpleMethod( Map<String, Integer> testMap) { //code logic } } Then I attempt to use this to invoke the private method: //Hashmap Map <String, Integer> testMap = new HashMap <String, Integer>(); //method I want to invoke Method simpleMethod = TestClass.class.getDeclaredMethod("simpleMethod", Map.class); simpleMethod.setAccessible(true); simpleMethod.invoke(testClassObject, testMap); //Throws an IllegalArgumentException As you can see, it throws an IllegalArgumentException. I've attempted to cast the hashmap back to a map, but that didn't work. What am I doing wrong?

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  • LINQ method chaining and granular error handling

    - by Clafou
    I have a method which can be written pretty neatly through method chaining: return viewer.ServerReport.GetParameters() .Single(p => p.Name == Convention.Ssrs.RegionParamName) .ValidValues .Select(v => v.Value); However I'd like to be able to do some checks at each point as I wish to provide helpful diagnostics information if any of the chained methods returns unexpected results. To achieve this, I need to break up all my chaining and follow each call with an if block. It makes the code a lot less readable. Ideally I'd like to be able to weave in some chained method calls which would allow me to handle unexpected outcomes at each point (e.g. throw a meaningful exception such as new ConventionException("The report contains no parameter") if the first method returns an empty collection). Can anyone suggest a simple way to achieve such a thing?

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  • Can a C# method chain be "too long"?

    - by ccornet
    Not in terms of readability, naturally, since you can always arrange the separate methods into separate lines. Rather, is it dangerous, for any reason, to chain an excessively large number of methods together? I use method chaining primarily to save space on declaring individual one-use variables, and traditionally using return methods instead of methods that modify the caller. Except for string methods, those I kinda chain mercilessly. In any case, I worry sometimes about the impact of using exceptionally long method chains all in one line. Let's say I need to update the value of one item based on someone's username. Unfortunately, the shortest method to retrieve the correct user looks something like the following. SPWeb web = GetWorkflowWeb(); SPList list2 = web.Lists["Wars"]; SPListItem item2 = list2.GetItemById(3); SPListItem item3 = item2.GetItemFromLookup("Armies", "Allied Army"); SPUser user2 = item2.GetSPUser("Commander"); SPUser user3 = user2.GetAssociate("Spouse"); string username2 = user3.Name; item1["Contact"] = username2; Everything with a 2 or 3 lasts for only one call, so I might condense it as the following (which also lets me get rid of a would-be-superfluous 1): SPWeb web = GetWorkflowWeb(); item["Contact"] = web.Lists["Armies"] .GetItemById(3) .GetItemFromLookup("Armies", "Allied Army") .GetSPUser("Commander") .GetAssociate("Spouse") .Name; Admittedly, it looks a lot longer when it is all in one line and when you have int.Parse(ddlArmy.SelectedValue.CutBefore(";#", false)) instead of 3. Nevertheless, this is one of the average lengths of these chains, and I can easily foresee some of exceptionally longer counts. Excluding readability, is there anything I should be worried about for these 10+ method chains? Or is there no harm in using really really long method chains?

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  • Overloading operator>> to a char buffer in C++ - can I tell the stream length?

    - by exscape
    I'm on a custom C++ crash course. I've known the basics for many years, but I'm currently trying to refresh my memory and learn more. To that end, as my second task (after writing a stack class based on linked lists), I'm writing my own string class. It's gone pretty smoothly until now; I want to overload operator that I can do stuff like cin my_string;. The problem is that I don't know how to read the istream properly (or perhaps the problem is that I don't know streams...). I tried a while (!stream.eof()) loop that .read()s 128 bytes at a time, but as one might expect, it stops only on EOF. I want it to read to a newline, like you get with cin to a std::string. My string class has an alloc(size_t new_size) function that (re)allocates memory, and an append(const char *) function that does that part, but I obviously need to know the amount of memory to allocate before I can write to the buffer. Any advice on how to implement this? I tried getting the istream length with seekg() and tellg(), to no avail (it returns -1), and as I said looping until EOF (doesn't stop reading at a newline) reading one chunk at a time.

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  • applet communication using post method

    - by mithun1538
    I have an applet that is communicating with a servlet. I am communicating with the servlet using POST method. My problem is how do I send parameters to the servlet. Using GET method, this is fairly simple ( I just append the parameters to the URL after a ?). But using POST method how do I send the parameters, so that in the servlet side, I can use the statement : message = req.getParameter("msg"); In the applet side, I establish POST method connection as follows : URL url = new URL(getCodeBase(), "servlet"); URLConnection con = url.openConnection(); con.setDoInput(true); con.setDoOutput(true); con.setUseCaches(false); con.setRequestProperty("Content-Type","application/octet-stream");

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  • execute javascript method after method excution complete ?

    - by James123
    I want execute below callback()method after completion of process document.getElementById('btnDownload').click(); method. click() is the code behind method. That means, I mean after complete process of click() then excute callback() method. Because my modelpop is not hiding in code behind. So I want hide in javascript method. function LoadPopup() { // find the popup behavior this._popup = $find('mdlPopup'); // show the popup this._popup.show(); // synchronously run the server side validation ... document.getElementById('btnDownload').click(); callback(); } function callback() { this._popup = $find('mdlPopup'); // hide the popup this._popup.hide(); alert("hi"); }

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  • A controller method that calls a different method on the same controller

    - by justSteve
    I have a controller method: public ActionResult Details(int id) { Order order = OrderFacade.Instance.Load(id); return View(order); } that is used for 95% of possible invocations. For the other 5% i need to manipulate the value of id before passing to the facade. I'd like to create a separate method within this same controller that executes that manipulation and then calls this (Details) method. What would the signature of that method look like? What is the syntax to call the main Details method? public ??? ManipulatorMethod(int id) { [stuff that manipulates id] [syntax to call Details(manipulatedID)] } mny thx

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