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  • How to pass a member function to a function used in another member function?

    - by Tommaso Ferrari
    I found something about my problem, but I don't already understand very well. I need to do something like this: class T{ double a; public: double b; void setT(double par){ a=par; }; double funct(double par1) { return par1/a; } void exec(){ b=extfunct(funct, 10); } } double extfunct(double (*f)(double),double par2){ return f(par2)+5; } Operation and function are only for example, but the structure is that. The reason of this structure is that I have a precostituited class which finds the minimum of a gived function (it's extfunct in the example). So I have to use it on a function member of a class. I understood the difference between pointer to function and pointer to member function, but I don't understand how to write it. Thanks, and sorry for the poor explanation of the problem.

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  • asp:QueryStringParameter and empty query string parameter

    - by abatishchev
    I haveasp:GridView displaying client requests using asp:SqlDataSource. I want to limit displayed information by client: View.aspx has to display everything, View.aspx?client=1 has to display only requests from client ID #1. So I'm using <asp:QueryStringParameter Name="client" QueryStringField="client" /> for query "EXEC getRequests @client". Everything works properly when some client is specified. But don't - if not. I tested my SP using SSMS - it works properly in both cases - when parameter is specified and when it isn't (NULL passed explicitly). What have I do?

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  • How do I get class of an internal static class in another assembly?

    - by Echiban
    I have a class C in Assembly A like this: internal class C { internal static string About_Name { get { return "text"; } ... } I have about 20 such static properties. Is there a way, in an outside assembly, without using friend assembly attribute (.Net reflection only), get class C so I can invoke any of the static string properties like this: Class C = <some .Net reflection code>; string expected = C.About_Name; If that is not possible, a .Net reflection code to get the string property value directly will suffice, but not ideal. Thanks in advance!

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  • PHP explode and set to empty string the missing pieces

    - by Marco Demaio
    What's the best way to accomplish the following. I have strings in this format: $s1 = "name1|type1"; //(pipe is the separator) $s2 = "name2|type2"; $s3 = "name3"; //(in some of them type can be missing) Let's assume namen/typen are strings and they can not contain a pipe. Since I need to exctract the name/type separetly, I do: $temp = explode($s1, '|'); $name = $temp[0]; $type = ( isset($temp[1]) ? $temp[1] : '' ); Is there an easier (smarter whatever faster) way to do this without having to do isset($temp[1]) or count($temp). Thanks!

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  • Batch Create Java Class Stubs

    - by user344639
    Given a list of potential class names: 1. Alaska . . . 50. Wyoming Is there a tool that will create empty java class files for each with supplied parameters? I'm thinking of something like the "New...Class" dialog in Eclipse, only on steriods. :-) Thanks in advance, Kyle

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  • Why is 'virtual' optional for overridden methods in derived classes?

    - by squelart
    When a method is declared as virtual in a class, its overrides in derived classes are automatically considered virtual as well, and the C++ language makes this keyword virtual optional in this case: class Base { virtual void f(); }; class Derived : public Base { void f(); // 'virtual' is optional but implied. }; My question is: What is the rationale for making virtual optional? I know that it is not absolutely necessary for the compiler to be told that, but I would think that developers would benefit if such a constraint was enforced by the compiler. E.g., sometimes when I read others' code I wonder if a method is virtual and I have to track down its superclasses to determine that. And some coding standards (Google) make it a 'must' to put the virtual keyword in all subclasses.

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  • Can a WPF base class contain a control for a derived class?

    - by Number8
    Hello, I have several UserControls that have some of the same controls doing the same job. Is it possible to extract those controls into a base class? When I have tried it, I get an error that the definition in the generated .g.cs file will hide the parent def. What I would like to do: public class ctlBase : UserControl { internal CheckBox chkBox { get; set; } } In the .xaml of the derived class: <Grid> <CheckBox x:Name="chkBox" /> </Grid> public class DerivedCtl : ctlBase { } Thanks for any insights...

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  • Creating parameterized type object using annonymous class

    - by Andrei Fierbinteanu
    This might be a stupid question, but I just saw a question asking how to create a Type variable for a generic type. The consensus seemed to be that you should have a dummy method returning that type, and then use reflection to get it (in this case he wanted Map<String, String>). Something like this : public Map<String, String> dummy() { throw new Error(); } Type mapStringString = Class.forName("ThisClass").getMethod("dummy").getGenericReturnType(); My question is, not having used reflection that much, couldn't you just do something like: Type mapStringString = new ParameterizedType() { public Type getRawType() { return Map.class; } public Type getOwnerType() { return null; } public Type[] getActualTypeArguments() { return new Type[] { String.class, String.class }; } }; Would this work? If not, why not? And what are some of the dangers/problems if it does (besides being able to return some Type like Integer<String> which is obviously not possible.

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  • Get all descendants types of base class

    - by user1260827
    I have a base class called BaseEvent and several descendants classes: public class BaseEvent { // the some properties ... } [MapInheritance(MapInheritanceType.ParentTable)] public class Film : BaseEvent { // the some properties ... } [MapInheritance(MapInheritanceType.ParentTable)] public class Concert : BaseEvent { // the some properties ... } I have a code which create the BaseEvent instance at runtime: BaseEvent event = new BaseEvent(); //assign values for a properties ... baseEvent.XPObjectType = Database.XPObjectTypes.SingleOrDefault(t => t.TypeName == "MyApp.Module.BO.Events.BaseEvent"); Now, this event will be shows in BaseEvent list view. I want to do the following: when a user click Edit button then show in list view lookup field with all descendants types. And when user saves record change ObjectType to selected value. How can I do this? Thanks. PS. this is asp.net app.

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  • How does array class work in Java?

    - by oks16
    In Java, array is a class and extends Object. I am curious to know about this special array class. I don't find the class definition anywhere. Doing a getClass().getName() gives strange result. String[] array = new String[]{"one","two"}; System.out.println(array.getClass().getName()); // prints [Ljava.lang.String; I want to understand how array works under the hood. Is the array class definition hardcoded in the JVM? Any resources, books, links on this will be helpful. Thank you.

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  • C++ allocate objects on heap of base class with protected constructors via inheritance

    - by KRao
    I have a class with protected constructor: class B { protected: B(){}; }; Now I derive from it and define two static functions and I manage to actually create objects of the class B, but not on the heap: class A : public B { public: static B createOnStack() {return B();} //static B* createOnHeap() {return new B;} //Compile time Error on VS2010 }; B b = A::createOnStack(); //This works on VS2010! The question is: 1) Is VS2010 wrong in allowing the first case? 2) Is it possible to create objects of B without modifying B in any way (no friendship and no extra functions). I am asking, because it is possible to make something similar when dealing with instances of B and its member functions, see: http://accu.org/index.php/journals/296 Thank you in advance for any suggestion! Kind regards

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  • shared_ptr as class member

    - by idimba
    It's common to declared contained objects as a pointers to that class, while "forward declarating" them in header file. This in order to reduce physical dependencies in code. For example class B; // forward declaration class A { private: B* pB; }; Would it be good idea to declare such a member as shared_ptr, instead of naked pointer? I would prefer scoped_ptr, but AFAIKit it won't be in standard.

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  • static thread function access non-static class member in C++

    - by user397390
    Class Test{ int value; static void* thread_func(void* args){ value++; } void newthread(){ pthread_create(&thread_func,...); } } I'm trying to create a thread in Class Test. Therefore compiler forces me to make thread_func static. However I cannot access the non-static member "value" anymore. It says: invalid use of member 'Class::value' in static member function Is there a way around it?

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  • How to control manager class in Blackberry

    - by Keng
    Dear All, I have a problem when creating a UI on Blackberry. First, i try to create a ChatLayoutManager class extended from Manager class. My layout has three component: topfield, mainfield and bottom field. public class ChatLayoutManager extends Manager { private Field bottomField; private Field mainField; private Field titleField; public ChatLayoutManager(long style) { super(style); } protected void sublayout(int width, int height) { setExtent(width, height); int y = 0; if (bottomField != null) { layoutChild(bottomField, width, height); // This goes at the bottom of the screen setPositionChild(bottomField, 0, height-bottomField.getHeight()); height -= bottomField.getHeight(); } if (titleField != null) { layoutChild(titleField, width, height); // This goes at the top of the screen setPositionChild(titleField, 0, 0); height -= titleField.getHeight(); y += titleField.getHeight(); } if (mainField != null) { layoutChild(mainField, width, height); // This goes just below the title field (if any) setPositionChild(mainField, 0, y); } } public void setMainField(Field f) { mainField = f; add(f); } public void setBottomField(Field f) { bottomField = f; add(f); } public void setTitleField(Field f) { titleField = f; add(f); } Then i create another field (ChatField) extended from manager to add to mainfield in the ChatLayoutManager class which i have created above. public class ChatField extends Manager{ private Field _contentField[]; protected ChatField(){ super(Manager.HORIZONTAL_SCROLL | Manager.VERTICAL_SCROLL); } // TODO Auto-generated constructor stub} protected synchronized void sublayout(int width, int height) { // TODO Auto-generated method stub setExtent(width, height); int x = 0; int y = 0; if(_contentField.length > 0){ for(int i = 0 ;i<_contentField.length; i++){ //if(getManager() == this){ this.layoutChild(_contentField[i], _contentField[i].getWidth(), _contentField[i].getHeight()); this.setPositionChild(_contentField[i], x, y); if(_contentField[i++]!= null){ if ((_contentField[i].getWidth() + _contentField[i].getWidth()) >= width){ x = 0; y += _contentField[i].getHeight(); } else{ x += _contentField[i].getWidth(); } } //} } } } public void setContentField(Field field[]){ _contentField = field; } } And now, when i create some fields(such as TextField, BitmapField ...) added to ChatField, the program has an error "Field is not a child of this manager". The reason is when the framework invokes the sublayout function of the ChatField class , when sublayout starts calling layoutChild function the manager of field is not ChatField but ChatlayoutManager. I've experience hard time trying to resolve this problem, still I have no solution. Anybody can give me some suggestions? I really appreciate.

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  • Can C# make my class look like another class?

    - by Vaccano
    I have a class that look like this: public class BasePadWI { public WorkItem WorkItemReference { get; set; } .... Other stuff ...... } I then have a dictionary that is defined like this: public Dictionary<BasePadWI, Canvas> Pad { get; set; } I would then like to make a call like this: List<WorkItem> workItems = Pad.Keys.ToList(); (Note: WorkItem is a sealed class, so I cannot inherit.) Is there some trickery that I could do in the class to make it look like a WorkItem? I have done this in the mean time: List<WorkItem> workItems = Pad.Keys.ToList().ConvertAll(x=>x.WorkItem);

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  • C#: Basic Reflection Class

    - by Mike
    I'm trying to find a basic reflection abstract class that will generate basic information about a class. I have a template of how I would like it to work: class ThreeList<string,Type,T> { string Name {get; set;} Type Type {get; set;} T Value {get; set;} } abstract class Reflect<T> { List<ThreeList<string, Type, T> list; ReturnType MethodName() { foreach (System.Reflection.PropertyInfo prop in this.GetType().GetProperties()) { object value = prop.GetValue(this, new object[] { }); list.Add(prop.Name, prop.DeclaringType, value); } } } I'd like it to be infinitely deep, recursively calling Reflect. Something like this has to exist. I'm not really opposed to coding it myself, I just don't want to go through the hassle if its already been done.

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  • Member variable in C++ class that is always constant for all objects of that class?

    - by user1799323
    I'm constructing a class where I have three member variables that I want to always be the same value NO MATTER WHAT. I have class foo{ public: double var_1, var_2, var_3; double x=1, y=2, z=3; [functions go here] }; that gave me an error since I can't initialize a variable like that. But I want x, y and z to always be 1, 2 and 3 respectively. I tried defining them outside the class but that doesn't work since I want them to be member variables of the class. How do I do this?

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  • MySQL update query, how to skip empty values?

    - by Pawel
    I've got such query: $sql = "UPDATE test_accs SET acc_owner = '$owner_id', acc_policy_version = '$version', acc_policy_last_update = '$approved', acc_policy_next_update = '$renewed' WHERE acc_id = '1'"; Now, all of these values on the web folmular are optional, one can set one of these values, two, or so. Now, after I submit the form, it goes in the query like that: UPDATE test_accs SET acc_owner = '2', acc_policy_version = '1.2', acc_policy_last_update = '2012-12-19', acc_policy_next_update = '2012-12-18' WHERE acc_id = '1' It works only when I submit all values from the form. Can you please show me how could it work even if not all the values has been sent, just for example one of them? When I set one value (f.ex. policy version), it looks like that: UPDATE test_accs SET acc_owner = '', acc_policy_version = '1.2', acc_policy_last_update = '', acc_policy_next_update = '' WHERE acc_id = '1' and it isn't working. It might be possible cause of the acc_owner table values? #1366 - Incorrect integer value: '' for column 'acc_owner' at row 1 Thanks in advice.

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  • Undefined / Uninitialized default values in a class

    - by Jir
    Let's suppose you have this class: class A { public: A () {} A (double val) : m_val(val) {} ~A () {} private: double m_val; }; Once I create an instance of A, how can I check if m_val has been initialized/defined? Put it in other words, is there a way to know if m_val has been initialized/defined or not? Something along the lines of the defined operator in Python, I suppose. (But correct me if I'm wrong.) I thought of modifying the class and the c-tors the following way: class A { public: A () : defined(false) {} A (double val) : m_val(val), defined(true) {} ~A () {} private: double m_val; bool defined; }; How do you rate this solution? Any suggestion? TIA, Chris

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  • Pass parameters to Flash Main (Document) class

    - by loto
    In Flash CSn/AS3 you associate a Main class with a flash file which when loaded in the flash player "automatically creates an instance of the program's main class." I'd like to know how to pass arguments to the main class, since you don't write it yourself (you put its name in the Document textfield in the IDE).

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