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  • Attribute vector emptying itself

    - by ravloony
    Hello, I have two classes, derived from a common class. The common class has a pure virtual function called execute(), which is implemented in both derived classes. In the inherited class I have an attribute which is a vector. In both execute() methods I overwrite this vector with a result. I access both classes from a vector of pointers to their objects. The problem is when I try to access the result vector form outside the objects. In one case I can get the elements (which are simply pointers), in the other I cannot, the vector is empty. Code: class E; class A{ protected: vector<E*> _result; public: virtual void execute()=0; vector<E*> get_result(); }; vector<E*> A::get_result() { return _result; } class B : public A { public: virtual void execute(); }; B::execute() { //... _result = tempVec; return; } class C : public A { public: virtual void execute(); }; C::execute() { //different stuff to B _result = tempvec; return; } main() { B* b = new B(); C* c = new C(); b->execute(); c->execute(); b->get_result();//returns full vector c->get_result(); //returns empty vector!! } I have no idea what is going on here... I have tried filling _result by hand from a temp vector in the offending class, doing the same with vector::assign(), nothing works. And the other object works perfectly. I must be missing something.... Any help would be greatly appreciated.

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  • Session vs singleton pattern

    - by chobo
    Hi, I have a web application where I would like to pull user settings from a database and store them for Global access. Would it make more sense to store the data in a Singleton, or a Session object? What's the difference between the two? Is it better to store the data as an object reference or break it up into value type objects (ints and strings)? Thanks!

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  • What are the standard practices for throwing Javascript Exceptions?

    - by T.R.
    w3schools says that exceptions can be strings, integers, booleans, or objects, but the example given doesn't strike me as good practice, since exception type checking is done through string comparison. Is this the preferred method of exception handling in Javascript? Are there built-in exception types (like NullPointerException)? (if so, what are they, what kind of inheritance do they use, and are they preferred over other options?)

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  • ZendFramework Zend_Form_Element_File setDestination vs rename filter

    - by bibstha
    The code says Zend_Form_element_File::setDestination() is depricated and to use the rename filter. However the rename filter is currently codes such that when path is set, only temporary name is given. Original filename is lost. <?php $file = new Zend_Form_Element_File(); $file->setDestination('/var/www/project/public'); ?> vs <?php $file = new Zend_Form_Element_File(); $file->addFilter('Rename', array('target' => '/var/www/project/public')); ?> Any solution to upload files so that it preserves original filename structure but checks for existing file and appends _1.ext or _2.ext?

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  • How to integrate camera image into physics engine?

    - by Pedro
    I recently came across this and would like to implement something similar. The basic approach is clear: I have to threshold the image and check if a virtual object collides with the remaining foreground. Instead of implementing the physics myself, I'd like use an engine like Box2D. But how do I integrate the thresholded image into the physics engine so it is possible to interact with virtual objects?

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  • how to use oracle package to get rid of Global Temp table

    - by john
    I have a sample query like below: INSERT INTO my_gtt_1 (fname, lname) (select fname, lname from users) In my effort to getting rid of temporary tables I created a package: create or replace package fname_lname AS Type fname_lname_rec_type is record ( fname varchar(10), lname varchar(10) ); fname_lname_rec fname_lname_rec_type Type fname_lname_tbl_type is table of fname_lname_rec_type; function fname_lname_func ( v_fnam in varchar2, v_lname in varchar2 )return fname_lname_tbl_type pipelined; being new to oracle...creating this package took a long time. but now I can not figure out how to get rid of the my_gtt_1 how can i say... INSERT INTO <newly created package> (select fnma, name from users)

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  • When should I implement IDisposeable?

    - by Bobby
    What is the best practice for when to implement IDisposeable? Is the best rule of thumb to implement it if you have one managed object in the class, or does it depend if the object was created in the class or just passed in? Should I also do it for classes with no managed objects at all?

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  • Relational Database arrays (H2, Java)

    - by Daddy Warbox
    I seem to have two options on how to implement arrays, and I want to know which I should go with: Use the ARRAY data type and (from what I understand) effectively serialize data objects into the database (which in my case are just wrapped primitive types; don't know of another way to make this work). Use a separate table and map with foreign keys for each array item. If you have experience with this (especially with H2), which would you recommend?

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  • Why can't your switch statement data type be long Java?

    - by Fostah
    Here's an excerpt from Sun's Java tutorials: A switch works with the byte, short, char, and int primitive data types. It also works with enumerated types (discussed in Classes and Inheritance) and a few special classes that "wrap" certain primitive types: Character, Byte, Short, and Integer (discussed in Simple Data Objects ). There must be a good reason why the long primitive data type is not allowed. Anyone know what it is?

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  • JavaScript date comparisons

    - by Kyle
    I am new to the lower level useful functions of JavaScript, and I find myself needing to compare two date objects, but within an hourly range. For example, if Date1 is less then two hours until (or from) Date2. How could this be done?

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  • What will be the OOP approach? (or YOUR approach?)

    - by hsmit
    I'm having difficulties with some general OOP & Java approach. There are various ways to let classes/objects communicate with each other. To give a simple example: I need object A to perform action X. Object A needs P, Q and R to perform this action X. Will then Object A retrieve P, Q and R by itself (within action X), or must these values be parameters for action X?

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  • Should the argument be passed by reference in this .net example?

    - by Hamish Grubijan
    I have used Java, C++, .Net. (in that order). When asked about by-value vs. by-ref on interviews, I have always done well on that question ... perhaps because nobody went in-depth on it. Now I know that I do not see the whole picture. I was looking at this section of code written by someone else: XmlDocument doc = new XmlDocument(); AppendX(doc); // Real name of the function is different AppendY(doc); // ditto When I saw this code, I thought: wait a minute, should not I use a ref in front of doc variable (and modify AppendX/Y accordingly? it works as written, but made me question whether I actually understand the ref keyword in C#. As I thought about this more, I recalled early Java days (college intro language). A friend of mine looked at some code I have written and he had a mental block - he kept asking me which things are passed in by reference and when by value. My ignorant response was something like: Dude, there is only one kind of arg passing in Java and I forgot which one it is :). Chill, do not over-think and just code. Java still does not have a ref does it? Yet, Java hackers seem to be productive. Anyhow, coding in C++ exposed me to this whole by reference business, and now I am confused. Should ref be used in the example above? I am guessing that when ref is applied to value types: primitives, enums, structures (is there anything else in this list?) it makes a big difference. And ... when applied to objects it does not because it is all by reference. If things were so simple, then why would not the compiler restrict the usage of ref keyword to a subset of types. When it comes to objects, does ref serve as a comment sort of? Well, I do remember that there can be problems with null and ref is also useful for initializing multiple elements within a method (since you cannot return multiple things with the same easy as you would do in Python). Thanks.

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  • LINQ-to-SQL eagerly load entire object graph

    - by Paddy
    I have a need to load an entire LINQ-to-SQL object graph from a certain point downwards, loading all child collections and the objects within them etc. This is going to be used to dump out the object structure and data to XML. Is there a way to do this without generating a large hard coded set of DataLoadOptions to 'shape' my data?

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  • Is there a straightforward way to have a thread-local instance variable?

    - by Dan Tao
    With the ThreadStatic attribute I can have a static member of a class with one instance of the object per thread. This is really handy for achieving thread safety using types of objects that don't guarantee thread-safe instance methods (e.g., System.Random). It only works for static members, though. Is there any straightforward way to declare a class member as thread-local, meaning, each class instance gets an object per thread?

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  • Excel worksheet error

    - by developer
    Hi, I am trying to create dynamic excel sheet, with the help of php using XML Spreadsheet. But when I try to open the dynamically created excel sheet I keep on getting error that says 'Unable to load worksheet, problem with worksheet settings'. When I try to look at the log file it had created it shows the below text, XML ERROR in Worksheet Setting REASON: Bad Value FILE: C:\Documents and Settings\UserName\Local Settings\Temporary Internet Files\Content.IE5\5XZ039FS\output[3].xls GROUP: Worksheet TAG: Table ATTRIB: ExpandedRowCount VALUE: 4 Can anybody tell what does the above error mean and how do I remove it?

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  • Query Entity Framework 4

    - by nick
    Hi, Is it possible to run a query on an EF4.0 data context and get all objects of a certain type? Say the context has books, genres & authors but I only have a generic parameter, t. Is it possible to get all of type just by using this t? I don't think it is :(

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  • Calling constructors in c++ without new

    - by Nils
    I've often seen that people create objects in C++ using Thing myThing("asdf"); Instead of Thing myThing = myThing("asdf"); This seems to work (using gcc), at least as long as there are no templates involved. My question now, is the first line correct and if so should I use it?

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  • how to get variable stored in another object using objective c

    - by mac
    Hi All SaveNotes *saveNotes = [[SaveNotes alloc]initWithTitleString:title descrString:descr]; [titleDescrObjects addObject:saveNotes]; [saveNotes release]; from the above code i have saved title,descr to a class SaveNotes , and then i have stored that object in my NSMutableArray - titleDescrObjects, Its working fine, i need to get particular objects "descr" alone, how to get the descr from objectAtIndex:i i am trying for (int i=0; i<[titleDescrObjects count]; i++) { NSLog(@"\n ((%@))\n",[titleDescrObjects objectAtIndex:i].descr); } Thanks in advance,

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  • Print layout of C++ object with g++ compiler

    - by zaheer
    Is there a way to print the layout of a C++ object using the g++ compiler or any other means. A simplified example (assuming int takes 4 bytes) class A{ int a; }; class B:public A{ int b; } so the output would be A - 0 4 + a + B- 0 4 8 + A.a + b + It would be useful to understand the layout of objects (in my case virtual machine code). Thanks in advance. Regards, Zaheer

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  • empty base class optimization

    - by FredOverflow
    Two quotes from the C++ standard, §1.8: An object is a region of storage. Base class subobjects may have zero size. I don't think a region of storage can be of size zero. That would mean that some base class subobjects aren't actually objects. Opinions?

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  • Building a decision-making game in jQuery? Where would I store data....

    - by redconservatory
    I built a slideshow/decision-making game in Flash but would like to try to redo it using jQuery. The slideshow part seems simple enough, however I have a series of user decisions that I'm not sure how to approach. In flash, if the user makes a decision, I would just store this in a variable or shared local objects, is this the same for jQuery? i.e. mix regular javascript variables with the jQuery?

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  • What's the difference between C and C++

    - by Dinah
    I know that C++ has the concept of objects but C doesn't. I also know that pretty much all there is to know about C fits into K & R but the C++ library is vastly more complex. There have got to be other big differences though. What are the major differences between C and C++?

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