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  • Returning a static array without using a class field

    - by Bart Friederichs
    I have the following base and derived (partial, for sake of brevity) classes: class Base { public abstract int[] someArray { get; } } class Derived : Base { private readonly static int[] _someArray = new int[] { 1,2,3,4 }; public override int[] someArray { get { return _someArray; } } } What I would like now, is put the new int[] { 1,2,3,4 } in the return part of the getter. But, that would create a new array every time the getter is called. Is it possible to directly return some kind of object, which stays the same for all objects of class Derived ? Something along the lines of (I know this is invalid C#): get { return (int[]) { 1, 2, 3, 4 }; }

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  • Make Java parent class not part of the interface

    - by Bart van Heukelom
    (This is a hypothetical question for discussion, I have no actual problem). Say that I'm making an implementation of SortedSet by extending LinkedHashMap: class LinkedHashSortedMapThing extends LinkedHashMap implements SortedSet { ... } Now programmers who use this class may do LinkedHashMap x = new LinkedHashSortedMapThing(); But what if I consider the extending of LinkedHashMap an implementation detail, and do not want it to be a part of the class' contract? If people use the line above, I can no longer freely change this detail without worrying about breaking existing code. Is there any way to prevent this sort of thing, other than favouring composition over inheritance (which is not always possible due to private/protected members)?

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  • PHP Classes: parent/child communication

    - by Fffff
    Hi all, I'm having some trouble extending Classes in PHP. Have been Googling for a while. $a = new A(); $a->one(); $a->b1(); // something like this, or... class A { public $test1; public function one() { echo "this is A-one"; $this->two(); $parent->two(); $parent->B->two(); // ...how do i do something like this (prepare it for using in instance $a)? } } class B extends A { public $test2; public function two($test) { echo "this is B-two"; } } I'm ok at procedural PHP.

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  • C#: reflection alternative for switch on enum in order to select namespace/class

    - by Am
    Hi, I have an interface named IHarvester. There are 3 implementations of that interface, each under their own namespace: Google Yahoo Bing A HarvesterManager uses the given harvester. It knows the interface and all 3 implementations. I want some way of letting the class user say in which harvester it wants to use. And in the code select that implementation, without a switch-case implementation. Can reflection save my day? Here is the code bits: // repeat for each harvester namespace Harvester.Google { public abstract class Fetcher : BaseHarvester, IInfoHarvester {...} } public enum HarvestingSource { Google, Yahoo, Bing, } class HarvesterManager { public HarvestingSource PreferedSource {get;set;} public HarvestSomthing() { switch (PreferedSource) .... // awful... } } Thanks.

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  • Perl - Calling subclass constructor from superclass (OO)

    - by Emmel
    This may turn out to be an embarrassingly stupid question, but better than potentially creating embarrassingly stupid code. :-) This is an OO design question, really. Let's say I have an object class 'Foos' that represents a set of dynamic configuration elements, which are obtained by querying a command on disk, 'mycrazyfoos -getconfig'. Let's say that there are two categories of behavior that I want 'Foos' objects to have: Existing ones: one is, query ones that exist in the command output I just mentioned (/usr/bin/mycrazyfoos -getconfig`. Make modifications to existing ones via shelling out commands. Create new ones that don't exist; new 'crazyfoos', using a complex set of /usr/bin/mycrazyfoos commands and parameters. Here I'm not really just querying, but actually running a bunch of system() commands. Affecting changes. Here's my class structure: Foos.pm package Foos, which has a new($hashref-{name = 'myfooname',) constructor that takes a 'crazyfoo NAME' and then queries the existence of that NAME to see if it already exists (by shelling out and running the mycrazyfoos command above). If that crazyfoo already exists, return a Foos::Existing object. Any changes to this object requires shelling out, running commands and getting confirmation that everything ran okay. If this is the way to go, then the new() constructor needs to have a test to see which subclass constructor to use (if that even makes sense in this context). Here are the subclasses: Foos/Existing.pm As mentioned above, this is for when a Foos object already exists. Foos/Pending.pm This is an object that will be created if, in the above, the 'crazyfoo NAME' doesn't actually exist. In this case, the new() constructor above will be checked for additional parameters, and it will go ahead and, when called using -create() shell out using system() and create a new object... possibly returning an 'Existing' one... OR As I type this out, I am realizing it is perhaps it's better to have a single: (an alternative arrangement) Foos class, that has a -new() that takes just a name -create() that takes additional creation parameters -delete(), -change() and other params that affect ones that exist; that will have to just be checked dynamically. So here we are, two main directions to go with this. I'm curious which would be the more intelligent way to go.

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  • Operator Overloading for Queue C++

    - by Josh
    I was trying to use the overload operator method to copy the entries of one queue into another, but I am going wrong with my function. I don't know how else to access the values of the queue "original" any other way than what I have below: struct Node { int item; Node* next; }; class Queue { public: [...] //Extra code here void operator = (const Queue &original); protected: Node *front, *end; } void Queue::operator=(const Queue &original) { //THIS IS WHERE IM GOING WRONG while(original.front->next != NULL) { front->item = original.front->item; front->next = new Node; front = front->next; original.front = original.front->next; } }

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  • Are raw C++ pointers first class objects?

    - by Shailesh Kumar
    According to Wikipedia: An object is first-class when it: can be stored in variables and data structures can be passed as a parameter to a subroutine can be returned as the result of a subroutine can be constructed at runtime has intrinsic identity (independent of any given name) Somebody had once told me that raw pointers are not first class objects while smart pointers like std::auto_ptr are. But to me, a raw pointer (to an object or to a function) in C++ does seem to me to satisfy the conditions stated above to qualify as a first class object. Am I missing something?

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  • Confused about "override" vs. "new" in C#

    - by iTayb
    I'm having the following classes: class Base { public virtual void Print() { Console.WriteLine("Base"); } } class Der1 : Base { public new virtual void Print() { Console.WriteLine("Der1"); } } class Der2 : Der1 { public override void Print() { Console.WriteLine("Der2"); } } This is my main method: Base b = new Der2(); Der1 d1 = new Der2(); Der2 d2 = new Der2(); b.Print(); d1.Print(); d2.Print(); The output is Base, Der2, Der2. As far as I know, Override won't let previous method to run, even if the pointer is pointing to them. So the first line should output Der2 as well. However Base came out. How is it possible? How the override didn't work there?

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  • consts and other animals

    - by bks
    Hello i have a cpp code wich i'm having trouble reading. a class B is defined now, i understand the first two lines, but the rest isn't clear enough. is the line "B const * pa2 = pa1" defines a const variable of type class B? if so, what does the next line do? B a2(2); B *pa1 = new B(a2); B const * pa2 = pa1; B const * const pa3 = pa2; also, i'm having trouble figuring out the difference between these two: char const *cst = “abc”; const int ci = 15; thank you

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  • How to Execute Page_Load() in Page's Base Class?

    - by DaveDev
    I have the following PerformanceFactsheet.aspx.cs page class public partial class PerformanceFactsheet : FactsheetBase { protected void Page_Load(object sender, EventArgs e) { // do stuff with the data extracted in FactsheetBase divPerformance.Controls.Add(this.Data); } } where FactsheetBase is defined as public class FactsheetBase : System.Web.UI.Page { public MyPageData Data { get; set; } protected void Page_Load(object sender, EventArgs e) { // get data that's common to all implementors of FactsheetBase // and store the values in FactsheetBase's properties this.Data = ExtractPageData(Request.QueryString["data"]); } } The problem is that FactsheetBase's Page_Load is not executing. Can anyone tell me what I'm doing wrong? Is there a better way to get the result I'm after? Thanks

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  • Access parent class from custom attribute

    - by madcapnmckay
    Hi, Is it possible to access a parent class from within an attribute. For example I would like to create a DropDownListAttribute which can be applied to a property of a viewmodel class in MVC and then create a drop down list from an editor template. I am following a similar line as Kazi Manzur Rashid here. He adds the collection of categories into viewdata and retrieves them using the key supplied to the attribute. I would like to do something like the below, public ExampleDropDownViewModel { public IEnumerable<SelectListItem> Categories {get;set;} [DropDownList("Categories")] public int CategoryID { get;set; } } The attribute takes the name of the property containing the collection to bind to. I can't figure out how to access a property on the parent class of the attribute. Does anyone know how to do this? Thanks

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  • C++: Overload != When == Overloaded

    - by Mark W
    Say I have a class where I overloaded the operator == as such: Class A { ... public: bool operator== (const A &rhs) const; ... }; ... bool A::operator== (const A &rhs) const { .. return isEqual; } I already have the operator == return the proper Boolean value. Now I want to extend this to the simple opposite (!=). I would like to call the overloaded == operator and return the opposite, i.e. something of the nature bool A::operator!= (const A &rhs) const { return !( this == A ); } Is this possible? I know this will not work, but it exemplifies what I would like to have. I would like to keep only one parameter for the call: rhs. Any help would be appreciated, because I could not come up with an answer after several search attempts.

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  • FindBugs and CheckForNull on classes vs. interfaces

    - by ndn
    Is there any way to let FindBugs check and warn me if a CheckForNull annotation is present on the implementation of a method in a class, but not on the declaration of the method in the interface? import javax.annotation.CheckForNull; interface Foo { public String getBar(); } class FooImpl implements Foo { @CheckForNull @Override public String getBar() { return null; } } public class FindBugsDemo { public static void main(String[] args) { Foo foo = new FooImpl(); System.out.println(foo.getBar().length()); } } I just discovered a bug in my application due to a missing null check that was not spotted by FindBugs because CheckForNull was only present on FooImpl, but not on Foo, and I don't want to spot all other locations of this problem manually.

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  • Add UserControl To Page From Another Class

    - by Raika
    I have page and call method inside my page. I want to add some control to my page Control (not page itself) inside that method. namespace Program { public partail class Default : Page { protected void Page_Load(object sender, Eventargs e) { MyClass.Calling(this); } } } in another class namespace Program { public class MyClass { public static void Calling(Page page) { Textbox txt = new Textbox() // I want somthing like this. // page.PlaceHolder1.Controls.Add(txt); } } } Is this possible? My Default.aspx : <%@ Page Title="Home Page" MasterPageFile="~/Site.master" ... %> <asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent"> <asp:PlaceHolder ID="PlaceHolder1" runat="server"></asp:PlaceHolder> </asp:Content> Update: thanks to The King for help. his suggest work correctly if control is inside page not Content of master page like my defualt sample code.

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  • Find images that have a certain HTML class name

    - by Frederik Vig
    I have some markup that contains certain HTML image tags with the class featured. What I need is to find all those images, add an anchor tag around the image, set the href attribute of the anchor to the images src value (the image path), and lastly replace the images src value with a new value (I call a method that will return this value). <p>Some text here <img src="/my/path/image.png" alt="image description" class="featured" />. Some more text and another image that should not be modified <img src="/my/path/image2.png" alt="image description" /></p> Should become. <p>Some text here <a href="/my/path/image.png"><img src="/new/path/from/method.png" alt="image description" class="featured" /></a>. Some more text and another image that should not be modified <img src="/my/path/image2.png" alt="image description" /></p>

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  • How do you resolve the common collsision between type name and object name?

    - by Catskul
    Since the convention is to capitalize the first letter of public properties, the old c++ convention of initial capital for type names, and initial lowercase for non-type names does not prevent the classic name collision class FooManager { public BarManager BarManager { get; set; } // Feels very wrong. // Recommended naming convention? public int DoIt() { return Foo.Blarb + Foo.StaticBlarb; // 1st and 2nd Foo are two // different symbols } } class BarManager { public int Blarb { get; set; } public static int StaticBlarb { get; set; } } It seems to compile, but feels so wrong. Is there a recommend naming convention to avoid this?

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  • Internal class and access to external members.

    - by Knowing me knowing you
    I have question with this same title here but now as I'll present in code below this seems to behave in the opposite way to the way explained to me in my first question with the same title. Ok code: class LINT_rep { private: char* my_data_; //stores separately every single digit from a number public: class Iterator:public iterator<bidirectional_operator_tag,char*> { Iterator(const LINT_rep&); }; }; #include "StdAfx.h" #include "LINT_rep.h" LINT_rep::Iterator::Iterator(const LINT_rep& owner):myData_(nullptr) { myData_ = owner.my_data_; /* HERE I'M ACCESSING my_data WHICH IS PRIVATE AND THIS CODE COMPILES ON VS2010 ULTIMATE BUT IT SHOULDN'T BECAUSE my_data IS PRIVATE AND OTHER CLASS SHOULDN'T HAVE ACCESS TO IT'S PRIVATE MEMB. AS EXPLAINED TO ME IN QUESTION TO WHICH I;VE PROVIDED LINK. */ } Question in the code. Thanks.

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  • Automatically selecting and creating class objects

    - by Omin
    Lets say that we have a box class: class Box { private int width; private int height; //Box Constructor public Box( int height ) { this.height = height; width = 450; } } and a series of Box objects in our main: Box Box1 = new Box(147); Box Box2 = new Box(178); Box Box3 = new Box(784); Is there a way to use a "for" loop to go through these objects? Also, how would you make the computer create class objects for us? eg. create 10 objects using: for( int i=0; i>10; i++) { //method }

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  • Binding Data Template element to property on sub-class

    - by TerrorAustralis
    Hi guys, I have a class, for experiment sake call it foo() and another class, call it bar() I have a data template for class foo() defined in my xaml, but one of foo()'s properties is a bar() object such that foo() { Public string Name {get; set;} Public int ID {get; set;} Public bar barProp {get; set;} } and bar() { Public string Description{get; set;} } I want my data template of foo to display the Description property of bar. I have tried the simple <textblock Text="{Binding Path=barProp.Description}" /> and variants to no avail Seeking wisdom, DJ

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  • Assigning two strings together getting Access Read Violation

    - by Jay Bell
    I am trying to pass a string to a class mutator and set the private member to that string here is the code that is sending the string void parseTradePairs(Exchange::Currency *curr, std::string *response, int begin, int exit) { int start; int end; string temp; string dataResponse; CURL *tempCurl; initializeCurl(tempCurl); int location = response->find("marketid", begin); if(location <= exit) { start = location + 11; begin = response->find("label", start); end = begin - start - 3; findStrings(start, end, temp, response); getMarketInfo(tempCurl, temp, dataResponse); curr->_coin->setExch(temp); // here is the line of code that is sending the string dataResponse >> *(curr->_coin); curr->_next = new Exchange::Currency(curr, curr->_position + 1); parseTradePairs(curr->_next, response, begin, exit); } } and here is the mutator within the coin class that is receiving the string and assigning it to _exch void Coin::setExch(string exch) { _exch = exch; } I have stepped through it and made sure that exch has the string in it. "105" but soon as it hits _exch = exch; I get the reading violation. I tried passing as pointer as well. I do not believe it should go out of scope. and the string variable in the class is initialized to zero in the default constructor but again that should matter unless I am trying to read from it instead of writing to it. /* defualt constructor */ Coin::Coin() { _id = ""; _label = ""; _code= ""; _name = ""; _marketCoin = ""; _volume = 0; _last = 0; _exch = ""; } Exchange::Exchange(std::string str) { _exch = str; _currencies = new Currency; std::string pair; std::string response; CURL *curl; initializeCurl(curl); getTradePairs(curl, response); int exit = response.find_last_of("marketid"); parseTradePairs(_currencies, &response, 0, exit); } int main(void) { CURL *curl; string str; string id; Coin coin1; initializeCurl(curl); Exchange ex("cryptsy"); curl_easy_cleanup(curl); system("pause"); return 0; } class Exchange { public: typedef struct Currency { Currency(Coin *coin, Currency *next, Currency *prev, int position) : _coin(coin), _next(next), _prev(prev), _position(position) {} Currency(Currency *prev, int position) : _prev(prev), _position(position), _next(NULL), _coin(&Coin()){} Currency() : _next(NULL), _prev(NULL), _position(0) {} Coin *_coin; Currency *_next; Currency *_prev; int _position; }; /* constructor and destructor */ Exchange(); Exchange(std::string str); ~Exchange(); /* Assignment operator */ Exchange& operator =(const Exchange& copyExchange); /* Parse Cryptsy Pairs */ friend void parseTradePairs(Currency *curr, std::string *response, int begin, int exit); private: std::string _exch; Currency *_currencies; }; here is what i changed it to to fix it. typedef struct Currency { Currency(Coin *coin, Currency *next, Currency *prev, int position) : _coin(coin), _next(next), _prev(prev), _position(position) {} Currency(Currency *prev, int position) : _prev(prev), _position(position), _next(NULL), _coin(&Coin()){} Currency() { _next = NULL; _prev = NULL; _position = 0; _coin = new Coin(); } Coin *_coin; Currency *_next; Currency *_prev; int _position; };

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  • User Defined Class as a Template Parameter

    - by isurulucky
    Hi, I' m implementing a custom STL map. I need to make sure that any data type (basic or user defined) key will work with it. I declared the Map class as a template which has two parameters for the key and the value. My question is if I need to use a string as the key type, how can I overload the < and operators for string type keys only?? In template specialization we have to specialize the whole class with the type we need as I understand it. Is there any way I can do this in a better way?? What if I add a separate Key class and use it as the template type for Key? Thank You!!

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  • WPF DrawingVisual from my own class

    - by Robbskinizer
    Hi, Im trying to create my own class which contains a DrawingVisual, something like this public class MyObject { public DrawingVisual visual; public bool faceup; public bool flipped; } I have a drag and drop from a listview to a canvas, but when I try to get the object which back from the Canvas i only get the visual, not any of the other stuff in the class. How do i save "objects" and retreive it from a canvas? Im using my own MyCanvas which inheritance from Canvas, and using the AddVisualChild & AddLogicalChild etc. // Robbin

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  • How to avoid "incomplete implementation" warning in partial base class

    - by garph0
    I have created a protocol that my classes need to implement, and then factored out some common functionality into a base class, so I did this: @protocol MyProtocol - (void) foo; - (void) bar; @end @interface Base <MyProtocol> @end @interface Derived_1 : Base @end @interface Derived_2 : Base @end @implementation Base - (void) foo{ //something foo } @end @implementation Derived_1 - (void) bar{ //something bar 1 } @end @implementation Derived_2 - (void) bar{ //something bar 2 } @end In this way in my code I use a generic id<MyProtocol>. The code works (as long as Base is not used directly) but the compiler chokes at the end of the implementation of Base with a warning: Incomplete implementation of class Base Is there a way to avoid this warning or, even better, a more proper way to obtain this partially implemented abstract base class behavior in Objc?

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