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  • How does object of sub-class record information about its super-class the in a Virtual Inheritance

    - by Summer_More_More_Tea
    Hi there: I encounter this problem when tackling with virtual inheritance. I remember that in a non-virtual inheritance hierarchy, object of sub-class hold an object of its direct super-class. What about virtual inheritance? In this situation, does object of sub-class hold an object of its super-class directly or just hold a pointer pointing to an object of its super-class? By the way, why the output of the following code is: sizeof(A): 8 sizeof(B): 20 sizeof(C): 32 Code: #include <iostream> using namespace std; class A{ char k[ 3 ]; public: virtual void a(){}; }; class B : public virtual A{ char j[ 3 ]; public: virtual void b(){}; }; class C : public virtual B{ char i[ 3 ]; public: virtual void c(){}; }; int main( int argc, char *argv[] ){ cout << "sizeof(A): " << sizeof( A ) << endl; cout << "sizeof(B): " << sizeof( B ) << endl; cout << "sizeof(C): " << sizeof( C ) << endl; return 0; } Thanks in advance. Kind regards.

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  • How do I get a MessageBox like information window to appear in Java?

    - by John McClane
    I'm learning Java and I have no idea how to do this. I dragged a button on the form in Netbeans, double clicked it and it created this event: @Action public void HelloClickMethod() { JOptionPane.showMessageDialog(this, "The message!", "This is supposed to be the MessageBox title."); } This is the exception the IDE brings up. Cannot find symbol. Symbol: showMessageDialog() Edit 1 Now I changed it to this: @Action public void HelloClickMethod() { JOptionPane.showMessageDialog(this, "The message!", "This is supposed to be the MessageBox title.",JOptionPane.ERROR_MESSAGE); } However the IDE is saying I have an error in the word 'this'. "Cannot find symbol". I don't understand. Why is it so dificult and why are the errors so esoteric. :P

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  • Using a trigger to record audit information vs. stored procedure

    - by Germ
    Suppose you have the following... An ASP.NET web application that calls a stored procedure to delete a record. The table has a trigger on it that will insert an audit entry each time a record is deleted. I want to be able to record in the audit entry the username of who deleted the record. What would be the best way to go about achieving this? I know I could remove the trigger and have the delete stored procedure insert the audit entry prior to deleting but are there any other recommeded alternative? If a username was passed as a parameter to the delete stored procedure, is there anyway to get this value in the trigger that's excuted when the record is deleted? I'm just throwing this out there...

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  • What's the best practice for handling system-specific information under version control?

    - by Joe
    I'm new to version control, so I apologize if there is a well-known solution to this. For this problem in particular, I'm using git, but I'm curious about how to deal with this for all version control systems. I'm developing a web application on a development server. I have defined the absolute path name to the web application (not the document root) in two places. On the production server, this path is different. I'm confused about how to deal with this. I could either: Reconfigure the development server to share the same path as the production Edit the two occurrences each time production is updated. I don't like #1 because I'd rather keep the application flexible for any future changes. I don't like #2 because if I start developing on a second development server with a third path, I would have to change this for every commit and update. What is the best way to handle this? I thought of: Using custom keywords and variable expansion (such as setting the property $PATH$ in the version control properties and having it expanded in all the files). Git doesn't support this because it would be a huge performance hit. Using post-update and pre-commit hooks. Possibly the likely solution for git, but every time I looked at the status, it would report the two files as being changed. Not really clean. Pulling the path from a config file outside of version control. Then I would have to have the config file in the same location on all servers. Might as well just have the same path to begin with. Is there an easy way to deal with this? Am I over thinking it?

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  • where to store information like gender and year of birth?

    - by fayer
    i have users and i need them to specify a gender (male, female) and year of birth (1930, 1931...1999, 2000). i wonder where i should store these values: in the database? in php file? if i store them in the database i have to manually create all entries first. but a good thing is that the user table will have constraints so the gender field will always be male or female, it cannot be something else. if i store them in the php file (eg. as html) then i can easily add/remove values. but a con is that i dont have the constraints in database, so another value could be stored as gender by mistake, even though i could add validation in php backend so even if someone hacked the html it is not stored unless it's either male or female. what is best practice to do this? thanks

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  • Java. Writing a matrix in a file using column information. ( matrix transposition )

    - by Dmitry
    Hello, everybody! I have a file in which a matrix is stored. This file has a RandomAccessFile type. This matrix is stored by columns. I mean that in an i-th row of this matrix an i-th column (of a real matrix) is stored. There is an example: i-th row: 1 2 3 4 (in the file). That means that the real matrix has an i-th column: (1 2 3 4)(is transposed). I need to save this matrix in a natural way (by rows) in a new file, which I will then open with FileReader and display with TextArea. Do you know, how to do that? If so, please help =)

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  • Java: how to avoid circual references when dumping object information with reflection?

    - by Tom
    I've modified an object dumping method to avoid circual references causing a StackOverflow error. This is what I ended up with: //returns all fields of the given object in a string public static String dumpFields(Object o, int callCount, ArrayList excludeList) { //add this object to the exclude list to avoid circual references in the future if (excludeList == null) excludeList = new ArrayList(); excludeList.add(o); callCount++; StringBuffer tabs = new StringBuffer(); for (int k = 0; k < callCount; k++) { tabs.append("\t"); } StringBuffer buffer = new StringBuffer(); Class oClass = o.getClass(); if (oClass.isArray()) { buffer.append("\n"); buffer.append(tabs.toString()); buffer.append("["); for (int i = 0; i < Array.getLength(o); i++) { if (i < 0) buffer.append(","); Object value = Array.get(o, i); if (value != null) { if (excludeList.contains(value)) { buffer.append("circular reference"); } else if (value.getClass().isPrimitive() || value.getClass() == java.lang.Long.class || value.getClass() == java.lang.String.class || value.getClass() == java.lang.Integer.class || value.getClass() == java.lang.Boolean.class) { buffer.append(value); } else { buffer.append(dumpFields(value, callCount, excludeList)); } } } buffer.append(tabs.toString()); buffer.append("]\n"); } else { buffer.append("\n"); buffer.append(tabs.toString()); buffer.append("{\n"); while (oClass != null) { Field[] fields = oClass.getDeclaredFields(); for (int i = 0; i < fields.length; i++) { if (fields[i] == null) continue; buffer.append(tabs.toString()); fields[i].setAccessible(true); buffer.append(fields[i].getName()); buffer.append("="); try { Object value = fields[i].get(o); if (value != null) { if (excludeList.contains(value)) { buffer.append("circular reference"); } else if ((value.getClass().isPrimitive()) || (value.getClass() == java.lang.Long.class) || (value.getClass() == java.lang.String.class) || (value.getClass() == java.lang.Integer.class) || (value.getClass() == java.lang.Boolean.class)) { buffer.append(value); } else { buffer.append(dumpFields(value, callCount, excludeList)); } } } catch (IllegalAccessException e) { System.out.println("IllegalAccessException: " + e.getMessage()); } buffer.append("\n"); } oClass = oClass.getSuperclass(); } buffer.append(tabs.toString()); buffer.append("}\n"); } return buffer.toString(); } The method is initially called like this: System.out.println(dumpFields(obj, 0, null); So, basically I added an excludeList which contains all the previousely checked objects. Now, if an object contains another object and that object links back to the original object, it should not follow that object further down the chain. However, my logic seems to have a flaw as I still get stuck in an infinite loop. Does anyone know why this is happening?

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  • Ordering the results of a Hibernate Criteria query by using information of the child entities of the

    - by pkainulainen
    I have got two entities Person and Book. Only one instance of a specific book is stored to the system (When a book is added, application checks if that book is already found before adding a new row to the database). Relevant source code of the entities is can be found below: @Entity @Table(name="persons") @SequenceGenerator(name="id_sequence", sequenceName="hibernate_sequence") public class Person extends BaseModel { @Id @Column(name = "id") @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "id_sequence") private Long id = null; @ManyToMany(targetEntity=Book.class) @JoinTable(name="persons_books", joinColumns = @JoinColumn( name="person_id"), inverseJoinColumns = @JoinColumn( name="book_id")) private List<Book> ownedBooks = new ArrayList<Book>(); } @Entity @Table(name="books") @SequenceGenerator(name="id_sequence", sequenceName="hibernate_sequence") public class Book extends BaseModel { @Id @Column(name = "id") @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "id_sequence") private Long id = null; @Column(name="name") private String name = null; } My problem is that I want to find persons, which are owning some of the books owned by a specific persons. The returned list of persons should be ordered by using following logic: The person owning most of the same books should be at the first of the list, second person of the the list does not own as many books as the first person, but more than the third person. The code of the method performing this query is added below: @Override public List<Person> searchPersonsWithSimilarBooks(Long[] bookIds) { Criteria similarPersonCriteria = this.getSession().createCriteria(Person.class); similarPersonCriteria.add(Restrictions.in("ownedBooks.id", bookIds)); //How to set the ordering? similarPersonCriteria.addOrder(null); return similarPersonCriteria.list(); } My question is that can this be done by using Hibernate? And if so, how it can be done? I know I could implement a Comparator, but I would prefer using Hibernate to solve this problem.

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  • How to understand the BODYSTRUCTURE information returned by IMAP servers?

    - by Tony
    I'm using python's IMAPClient to retrieve email messages from IMAP server. One of the attributes I retrieve is BODYSTRUCTURE. However, I can't find any documentation on how to interpret the return values. Here's the body structure that IMAP server returns 16:12.679978 < FLAGS (NotJunk $NotJunk \Seen) BODYSTRUCTURE ((("TEXT" "PLAIN" ("CHARSET" "us-ascii") NIL NIL "QUOTED-PRINTABLE" 4888 170 NIL NIL NIL)("TEXT" "HTML" ("CHARSET" "us-ascii") NIL NIL "QUOTED-PRINTABLE" 32407 479 NIL NIL NIL) "ALTERNATIVE" ("BOUNDARY" "Apple-Mail=_3AAA7CD7-3B07-406A-83CB-2C7762C3306E") NIL NIL)("APPLICATION" "PKCS7-SIGNATURE" ("NAME" "smime.p7s") NIL NIL "BASE64" 2414 NIL ("ATTACHMENT" ("FILENAME" "smime.p7s")) NIL) "SIGNED" ("BOUNDARY" "Apple-Mail=_DF4FE6BB-F796-46D7-A593-9723F4315DD2" "MICALG" "sha1" "PROTOCOL" "application/pkcs7-signature") NIL NIL)) Here's the same body structure parsed to python type. "BODYSTRUCTURE": [ [ [ [ "TEXT", "PLAIN", [ "CHARSET", "us-ascii" ], null, null, "QUOTED-PRINTABLE", 4888, 170, null, null, null ], [ "TEXT", "HTML", [ "CHARSET", "us-ascii" ], null, null, "QUOTED-PRINTABLE", 32407, 479, null, null, null ], "ALTERNATIVE", [ "BOUNDARY", "Apple-Mail=_3AAA7CD7-3B07-406A-83CB-2C7762C3306E" ], null, null ], [ "APPLICATION", "PKCS7-SIGNATURE", [ "NAME", "smime.p7s" ], null, null, "BASE64", 2414, null, [ "ATTACHMENT", [ "FILENAME", "smime.p7s" ] ], null ] ], "SIGNED", [ "BOUNDARY", "Apple-Mail=_DF4FE6BB-F796-46D7-A593-9723F4315DD2", "MICALG", "sha1", "PROTOCOL", "application/pkcs7-signature" ], null, null ], The arrays don't seems to be constant length. What each element of the array stand for?

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  • how to remove all text nodes and only preserve structure information of a html page with nokogiri

    - by user58948
    I want to remove all text from html page that I load with nokogiri. For example, if a page has the following: <body><script>var x = 10;</script><div>Hello</div><div><h1>Hi</h1></div></body> I want to process it with Nokogiri and return html like the following after stripping the text like so: <body><script>var x = 10;</script><div></div><div><h1></h1></div></body> (THat is, remove the actual h1 text, text between divs, text in p elements etc, but keep the tags. also, dont remove text in the script tags.) How can I do that?

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  • Why is function's length information of other shared lib in ELF?

    - by minastaros
    Our project (C++, Linux, gcc, PowerPC) consists of several shared libraries. When releasing a new version of the package, only those libs should change whose source code was actually affected. With "change" I mean absolute binary identity (the checksum over the file is compared. Different checksum - different version according to the policy). (I should mention that the whole project is always built at once, no matter if any code has changed or not per library). Usually this can by achieved by hiding private parts of the included Header files and not changing the public ones. However, there was a case where just a delete was added to the destructor of a class TableManager (in the TableManager.cpp file!) of library libTableManager.so, and yet the binary/checksum of library libB.so (which uses class TableManager ) has changed. TableManager.h: class TableManager { public: TableManager(); ~TableManager(); private: int* myPtr; } TableManager.cpp: TableManager::~TableManager() { doSomeCleanup(); delete myPtr; // this delete has been added } By inspecting libB.so with readelf --all libB.so, looking at the .dynsym section, it turned out that the length of all functions, even the dynamically used ones from other libraries, are stored in libB! It looks like this (length is the 668 in the 3rd column): 527: 00000000 668 FUNC GLOBAL DEFAULT UND _ZN12TableManagerD1Ev So my questions are: Why is the length of a function actually stored in the client lib? Wouldn't a start address be sufficient? Can this be suppressed somehow when compiling/linking of libB.so (kind of "stripping")? We would really like to reduce this degree of dependency...

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  • How should i store availability calendar information in mysql? for [id] [date] [available/unavailab

    - by Haroldo
    I'm building a simple calendar for holiday cottages to show when they are booked or available. What would be the fastest mysql table design for this, bearing in mind when users mark dates as available/booked they will do so via a start date and an end date. i can see 2 obvious options Store 'booked' data for every day [more rows] or, store 'booked' data with 2 columns a start_date and end_date [more processing?] Which is best or is there another method i'm missing?

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  • How can I declare a pointer with filled information in C++?

    - by chacham15
    typedef struct Pair_s { char *first; char *second; } Pair; Pair pairs[] = { {"foo", "bar"}, //this is fine {"bar", "baz"} }; typedef struct PairOfPairs_s { Pair *first; Pair *second; } PairOfPairs; PairOfPairs pops[] = { {{"foo", "bar"}, {"bar", "baz"}}, //How can i create an equivalent of this NEATLY {&pairs[0], &pairs[1]} //this is not considered neat (imagine trying to read a list of 30 of these) }; How can I achieve the above style declaration semantics?

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  • How much information do pdb files contain? (C# / .NET)

    - by Silver Dragon
    Is is wise to redistribute the pdb files along with a commercial application? Occasionally, I'm using the stack trace to get a more detailed error reporting logs from the deployed applications; can this functionality be achieved without relying to those files? Also, how much hints of the original source code does these files contain? Would it be easier to reverse-engineer my application using it?

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  • Getting information about where c++ exceptions are thrown inside of catch block?

    - by tfinniga
    I've got a c++ app that wraps large parts of code in try blocks. When I catch exceptions I can return the user to a stable state, which is nice. But I'm not longer receiving crash dumps. I'd really like to figure out where in the code the exception is taking place, so I can log it and fix it. Being able to get a dump without halting the application would be ideal, but I'm not sure that's possible. Is there some way I can figure out where the exception was thrown from within the catch block? If it's useful, I'm using native msvc++ on windows xp and higher. My plan is to simply log the crashes to a file on the various users' machines, and then upload the crashlogs once they get to a certain size.

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  • How can I pass information between 2 different View Controllers?

    - by sagiftw
    Hi, This is a simple question: I have 2 different view controllers, and each one has its own data stored in its .m file. I want to take a value, for instance, an integer value (int i=3;) that is declared in ViewController1 and pass it to ViewController2, so I will be able to use that value in the second view controller. Can anyone please tell me how to do it? Thanks in advance, Sagiftw

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  • How to make use of Tags property of an xml node to get its information and attributes?

    - by user72731
    How would i make use of tags property of a node so that i can get the attributes of an xml node. I have to display an xml tree in a winform and then when i click on any node, its attributes should get displayed on a list box in same window. I want to make use of tags property, but for that i need to convert that tree node in the winform into an xml node. I wanted to store the tree node in the tag and then typecast that tag to an xml node. I dont know how to do it? I am a newbie at C# so there might be some discrpancy in language...please help

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