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  • Class basic operators

    - by swan
    Hi, Is it necessary to have a copy constructor, destructor and operator= in a class that have only static data member, no pointer class myClass{ int dm; public: myClass(){ dm = 1; } ~myClass(){ } // Is this line usefull ? myClass(const myClass& myObj){ // and that operator? this->dm = myObj.dm; } myClass& operator=(const myClass& myObj){ // and that one? if(this != &myObj){ this->dm = myObj.dm; } return *this; } }; I read that the compiler build one for us, so it is better to not have one (when we add a data member we have to update the operators)

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  • Performance when accessing class members

    - by Dr. Acula
    I'm writing something performance-critical and wanted to know if it could make a difference if I use: int test( int a, int b, int c ) { // Do millions of calculations with a, b, c } or class myStorage { public: int a, b, c; }; int test( myStorage values ) { // Do millions of calculations with values.a, values.b, values.c } Does this basically result in similar code? Is there an extra overhead of accessing the class members? I'm sure that this is clear to an expert in C++ so I won't try and write an unrealistic benchmark for it right now

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  • subscribing an event to a class object before initializing it.

    - by GN
    I have two classes class A and B.I have a delegate n event published in class B.The class B object is declared in class A.All he functionality dependes on the parameterised constru ctor of class B. Before initializing the object of class B i need to subscibe the event for it.how to do it? e.g public class B { public delegate void myDel(string); public event myDel myEvent; B(object obj) { ----------------- ------------------ } } class A { A objA; class XYZ objXYZ; void func() { objA.myEvent+=new myDel(); objA=new A(objXYZ); // hw to attain this? } }

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  • UDK "Error, Accessing a member of _'s within class through a context expression requires explicit 'O

    - by Ricket
    I get the following error in the UDK Frontend when I try to make my project: C:\UDK\UDK-2010-03\Development\Src\FixIt\Classes\ZInteraction.uc(58) : Error, Accessing a member of GameUISceneClient's within class through a context expression requires explicit 'Outer' The class ZInteraction extends Interaction. Line 58 is: GetSceneClient().ConsoleCommand("KEYNAME"@Key); What is the problem here? I am still investigating and I will update as I find out more. edit: Tried fixing the line up as class'UIRoot'.static.GetSceneClient().ConsoleCommand("KEYNAME"@Key); - no change.

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  • Searching the first few characters of every word within a string in C#

    - by user1704669
    I am new to Programming languages. I have a requirement where I have to return a record based on a search string. For e.g. I am having the following 3 records and my search string is 'Cal' 1)University of California 2)Pascal Institute 3)California University If I try string.Contains, all 3 are returned. If I try string.starts-with, I get only 3 but my requirement is I need #1 and #3 in the result. Thank you for your help. -Joel

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  • Push a detail view in UITableViewCell class

    - by luca
    My class inherit from UITableViewCell, i have make some custom transitions to push a new detail view when an image get selected. [UIView transitionWithView:self.masterView duration:0.5 options:UIViewAnimationOptionShowHideTransitionViews animations:^ { [self.masterView addSubview:self.detailImage]; } completion:nil]; My code works fine, the detailImage subview is shown with a transition, but this transition is not what i want exactly. What i want to perform is a simple transition from bottom to up. The list of UIViewAnimation doesn't contain such animation. Is there any way to use that transition without changing my class inheritance to UINavigationController ?

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  • Obj-C: Creating an object with a String name

    - by FnGreg7
    Hey all. I know this sounds simple, but I can't find a way to do it. I have a method in Obj-C that takes in a NSString and then should create a new class with the String as its title. -(DataModel *)createDataModel:(NSString *)dataModel_name { DataModel *[initWithString:dataModel_name] = [[DataModel alloc] init]; } I know I have some problems in this. For starters, I don't know how to define a return on an object whose name could change. Second, I know this doesn't compile considering the initWithString method is wrong. I just don't know what to do or what method to use so that I can create this DataModel object with the specified name...

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  • Detect if class has overloaded function fails on Comeau compiler

    - by Frank
    Hi Everyone, I'm trying to use SFINAE to detect if a class has an overloaded member function that takes a certain type. The code I have seems to work correctly in Visual Studio and GCC, but does not compile using the Comeau online compiler. Here is the code I'm using: #include <stdio.h> //Comeau doesnt' have boost, so define our own enable_if_c template<bool value> struct enable_if_c { typedef void type; }; template<> struct enable_if_c< false > {}; //Class that has the overloaded member function class TestClass { public: void Func(float value) { printf( "%f\n", value ); } void Func(int value) { printf( "%i\n", value ); } }; //Struct to detect if TestClass has an overloaded member function for type T template<typename T> struct HasFunc { template<typename U, void (TestClass::*)( U )> struct SFINAE {}; template<typename U> static char Test(SFINAE<U, &TestClass::Func>*); template<typename U> static int Test(...); static const bool Has = sizeof(Test<T>(0)) == sizeof(char); }; //Use enable_if_c to only allow the function call if TestClass has a valid overload for T template<typename T> typename enable_if_c<HasFunc<T>::Has>::type CallFunc(TestClass &test, T value) { test.Func( value ); } int main() { float value1 = 0.0f; int value2 = 0; TestClass testClass; CallFunc( testClass, value1 ); //Should call TestClass::Func( float ) CallFunc( testClass, value2 ); //Should call TestClass::Func( int ) } The error message is: no instance of function template "CallFunc" matches the argument list. It seems that HasFunc::Has is false for int and float when it should be true. Is this a bug in the Comeau compiler? Am I doing something that's not standard? And if so, what do I need to do to fix it?

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  • Call function from object instantiated in one class in another

    - by Dk43
    I have two classes, both of which need to be able to call the same instance of entitymanager class Engine { EntityManager::Entitymanager EManager; } And I need to add an object to a vector contained by this particular instance of Engine. What I want to do is be able to add a bullet spawned by the player to the vector that contains all my entities. class Player : Entity { void SpawnBullet() {Engine::EManager.Add(BULLET);} } The above returns this error: error: object missing in reference to ‘Engine::EManager’ How do I resolve this? Any help or pointers in the right direction would be much appreciated!

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  • C# compiler fails to recognize a class is implementing an interface

    - by Freek
    The following code fails to compile (using VS2010) and I don't see why. The compiler should be able to infer that List is 'compatible' (sorry for lack of a better word) with IEnumerable, but somehow it doesn't. What am I missing here? interface ITest { void Test(); } class TestClass : ITest { public void Test() { } } class Program { static void Test(IEnumerable<ITest> tests) { foreach(var t in tests) { Console.WriteLine(t); } } static void Main(string[] args) { var lst = new List<TestClass>(); Test(lst); // fails, why? Test(lst.Select(t=>t as ITest)); //success Test(lst.ToArray()); // success } }

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  • Size of a class with 'this' pointer

    - by psvaibhav
    The size of a class with no data members is returned as 1 byte, even though there is an implicit 'this' pointer declared. Shouldn't the size returned be 4 bytes(on a 32 bit machine)? I came across articles which indicated that 'this' pointer is not counted for calculating the size of the object. But I am unable to understand the reason for this. Also, if any member function is declared virtual, the size of the class is now returned as 4 bytes. This means that the vptr is counted for calculating the size of the object. Why is the vptr considered and 'this' pointer ignored for calculating the size of object?

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  • Combine First, Middle Initial, Last name and Suffix in T-SQL (No extra spaces)

    - by Paul
    I'm trying not to reinvent the wheel here...I have these four fields [tbl_Contacts].[FirstName], [tbl_Contacts].[MiddleInitial], [tbl_Contacts].[LastName], [tbl_Contacts].[Suffix] And I want to create a FullName field in a view, but I can't have extra spaces if fields are blank...So I can't do FirstName + ' ' + MiddleInitial + ' ' + LastName + ' ' + Suffix...Because if there is no middle initial or suffix I'd have 2 extra spaces in the field. I think I need a Case statement, but I thought someone would have a handy method for this...Also, the middleinitial and suffix may be null.

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  • Display database fields using first,1,2,..., last

    - by user195257
    Hello, Im trying to figure out how to achieve this: http://t-webdesign.co.uk/projects/geusa/industry_jobs.html Evenutually there will be lots of job postings under different industries, what would be the best way of implementing the 'page' links so i can display just 7 or 8 jobs at a time? Thank you

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  • TypeError: init_animals() takes 1 positional arguments but 2 were given

    - by libra
    I know this title look familiar to some old questions, but i've looked at every single one of them, none of them solves. And here is my codes: class Island (object):E,W,R,P def __init__(self, x, y): self.init_animals(y) def init_animals(y): pass isle = Island(x,y) However, i got the following error: Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 3, in __init__ TypeError: init_animals() takes 1 positional arguments but 2 were given Please tell me if i got any mistakes, im so confused by this. Best regards

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  • C# thread safety for class instances

    - by Steveng
    I am learning C# and I am confused with the thread safety of the copies of the class instances as below: eg: classA objA; classA objB = objA; objA.field1 = value2; //do I need lock around modification of field1? //let say we pass the objB to another thread objB.field1 = value1 //do I need a lock for objB because of the modification of field1? I am confused because coming from the background of C++, the class in C# is the reference type. If both objA and objB refer to the same memory underlying, then I would need a lock to protect the simultaneous writing to the field1. Could someone confirm with this or am I missing something? Thanks.

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  • Activate first workbook after closing second one?

    - by user1830217
    Open workbook A. Code in A opens workbook B. B is now the active WB. Code in B ends with ThisWorkBook.Close B closes, so A appears. Problem is, I can't get ANY Activate events in WB A to fire automatically after WB B closes. But if I close WB B manually, using mouse to 'x' out the WB, or via the menus, then WB A triggers Activate events. Somehow using VBA to close WB B prevents WB A Activate events from triggering. Same results in Excel 97 and 2003 Am I missing something, or is there a workaround?? Thanks! John

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  • Problems with first argument being string when overloading the + operator in C++

    - by Chris_45
    I have an selfmade Stringclass: //String.h String & operator = (const String &); String & operator = (char*); const String operator+ (String& s); const String operator+ (char* sA); . . //in main: String s1("hi"); String s2("hello"); str2 = str1 + "ok";//this is ok to do str2 = "ok" + str1;//but not this way //Shouldn't it automatically detect that one argument is a string and in both cases?

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  • Best way to test class methods without running __init__

    - by KenFar
    I've got a simple class that gets most of its arguments via init, which also runs a variety of private methods that do most of the work. Output is available either through access to object variables or public methods. Here's the problem - I'd like my unittest framework to directly call the private methods called by init with different data - without going through init. What's the best way to do this? So far, I've been refactoring these classes so that init does less and data is passed in separately. This makes testing easy, but I think the usability of the class suffers a little.

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  • How to first get different related values from diferent SQL tables (PHP)

    - by Ole Jak
    I am triig to fill options list. I have 2 tables USERS and STREAMS I vant to get all streams and get names of users assigned to that streams. Users consists of username and id Streams consists of id, userID, streamID I try such code: <?php global $connection; $query = "SELECT * FROM streams "; $streams_set = mysql_query($query, $connection); confirm_query($streams_set); $streams_count = mysql_num_rows($streams_set); while ($row = mysql_fetch_array($streams_set)){ $userid = $row['userID']; global $connection; $query2 = "SELECT email, username "; $query2 .= "FROM users "; $query2 .= "WHERE id = '{$userid}' "; $qs = mysql_query($query2, $connection); confirm_query($qs); $found_user = mysql_fetch_array($qs); echo ' <option value="'.$row['streamID'].'">'.$row['userID'].$found_user.'</option> '; } ?> But it does not return USER names from DB=( So what shall I do to this code to see usernames as "options" text?

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  • Calling inheriting class methods via interface.

    - by Stacey
    Given the scenario... interface IBase{ void Process(int value); } abstract class Base : IBase { public virtual void Process(int value){ throw new NotImplementedException(); } } class Implemented: Base, IBase { public void Process(int value) { // .. some code here.. } } I'm trying to write a loop similar to the following. foreach( Base b in CollectionOfImplemented ) { b.Process( // something will go here // ); } Trying this, it keeps calling Base.Process, instead of Implemented.Process; but the type in the collection is Implemented, not Base. Boxing it seems to work, but I was hoping to see if I could find a more intelligent approach to it, since the Collection will contain other types of objects that also inherit from Base.

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