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  • Logging class using delegates (NullReferenceException)

    - by Leroy Jenkins
    I have created a small application but I would now like to incorporate some type of logging that can be viewed via listbox. The source of the data can be sent from any number of places. I have created a new logging class that will pass in a delegate. I think Im close to a solution but Im receiving a NullReferenceException and I don’t know the proper solution. Here is an example of what Im trying to do: Class1 where the inbound streaming data is received. class myClass { OtherClass otherClass = new OtherClass(); otherClass.SendSomeText(myString); } Logging Class class OtherClass { public delegate void TextToBox(string s); TextToBox textToBox; Public OtherClass() { } public OtherClass(TextToBox ttb) { textToBox = ttb; } public void SendSomeText(string foo) { textToBox(foo); } } The Form public partial class MainForm : Form { OtherClass otherClass; public MainForm() { InitializeComponent(); otherClass = new OtherClass(this.TextToBox); } public void TextToBox(string pString) { listBox1.Items.Add(pString); } } Whenever I receive data in myClass, its throwing an error. Any help you could give would be appreciated.

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  • Intellisense for custom config section problem with namespaces

    - by Quick Joe Smith
    I have just rolled a custom configuration section, created an accompanying schema document for Intellisense and added it to the Web.config's Schemas property as per Michael Stum's answer to another similar question. Unfortunately, and possibly due to me creating the XSD by hand with limited knowledge, the Intellisense relies on an xmlns attribute pointing to my XSD file's namespace being present in the custom config element. However, when running the project I get an Unrecognized attribute 'xmlns'. Note that attribute names are case-sensitive error. I could probably just modify my XSD file to define the xmlns attribute for that element, however I am wondering if this is just a bandaid fix to a larger problem. I must confess I don't have a very good understanding of XML namespaces so this might be an oppportunity to set me straight on a few things. Here is the attributes for my XSD file's root xs:schema element: <xs:schema id="awesomeConfig" targetNamespace="http://awesome.com/schemas" xmlns="http://awesome.com/schemas" elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema"> ... </xs:schema> And on creating the element in the Web.config file, Visual Studio 2008 automatically appends: <awesomeConfig xmlns="http://awesome.com/schemas"></awesomeConfig> So have I misunderstood the meaning of the xs:schema attributes at all, or is the proper solution as simple as it seems?

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  • Database Error Handling: What if You have to Call Outside service and the Transaction Fails?

    - by Ngu Soon Hui
    We all know that we can always wrap our database call in transaction ( with or without a proper ORM), in a form like this: $con = Propel::getConnection(EventPeer::DATABASE_NAME); try { $con->begin(); // do your update, save, delete or whatever here. $con->commit(); } catch (PropelException $e) { $con->rollback(); throw $e; } This way would guarantee that if the transaction fails, the database is restored to the correct status. But the problem is that let's say when I do a transaction, in addition to that transaction, I need to update another database ( an example would be when I update an entry in a column in databaseA, another entry in a column in databaseB must be updated). How to handle this case? Let's say, this is my code, I have three databases that need to be updated ( dbA, dbB, dbc): $con = Propel::getConnection("dbA"); try { $con->begin(); // update to dbA // update to dbB //update to dbc $con->commit(); } catch (PropelException $e) { $con->rollback(); throw $e; } If dbc fails, I can rollback the dbA but I can't rollback dbb. I think this problem should be database independent. And since I am using ORM, this should be ORM independent as well. Update: Some of the database transactions are wrapped in ORM, some are using naked PDO, oledb ( or whatever bare minimum language provided database calls). So my solution has to take care this. Any idea?

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  • iphone crash log with dSym not loading debug information

    - by AngeDeLaMort
    Hello, I was trying to see why my application crashed on the device (iPhone) using the dSym generated along the executable (in ad hoc), but I don't know why, there isn't any useful information. It seems that "Organizer" is able to find the appropriate dSym and translate some data into more readable one, but when it comes to my application, I just have an address. Since I know how to reproduce it, I've tried to setup my build so it can help me in the future. So, I've tried to find if I had all the proper flags set int the project build properties and everything seems fine. So after doing some research, it seems that all information are stripped during link time and the dSym seems completely useless. I've played with some flags, but nothing changed. So, is there something special to do in order to get the crash file human readable? Or is it impossible in the ad hoc setting? The closest thing near to work that I've done was to build a debug version and look up the address in it. At least it seems to give the right file. So, I made a sample app and here what I have: (the line I want is #4): Thread 0 Crashed: 0 libobjc.A.dylib 0x00003ebc objc_msgSend + 20 1 UIKit 0x0005c970 -[UIView dealloc] + 60 2 UIKit 0x0005c840 -[UIImageView dealloc] + 76 3 CoreFoundation 0x0003963a -[NSObject release] + 28 4 MyApplication 0x000046a6 0x1000 + 13990 5 UIKit 0x00069750 -[UIViewController view] + 44 6 MyApplication 0x000053fa 0x1000 + 17402 The crash is made using 2 successive releases on an object. Thanks in advance.

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  • Confused as to use a class or a function: Writing XML files using lxml and Python

    - by PulpFiction
    Hi. I need to write XML files using lxml and Python. However, I can't figure out whether to use a class to do this or a function. The point being, this is the first time I am developing a proper software and deciding where and why to use a class still seems mysterious. I will illustrate my point. For example, consider the following function based code I wrote for adding a subelement to a etree root. from lxml import etree root = etree.Element('document') def createSubElement(text, tagText = ""): etree.SubElement(root, text) # How do I do this: element.text = tagText createSubElement('firstChild') createSubElement('SecondChild') As expected, the output of this is: <document> <firstChild/> <SecondChild/> </document> However as you can notice the comment, I have no idea how to do set the text variable using this approach. Is using a class the only way to solve this? And if yes, can you give me some pointers on how to achieve this?

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  • How do I use HttpWebRequest GET method w/ ContentType="application/json"

    - by Stephen Patten
    Hello, This one is real simple, run this Silverlight4 example with the ContentType property commented out and you'll get back a response from from my service in xml. Now uncomment the property and run it and you'll get an ProtocolViolationException, what should happen is the service returns JSON formatted data. HttpWebRequest wreq = (HttpWebRequest)WebRequestCreator.ClientHttp.Create(new Uri("http://stephenpattenconsulting.com/Services/GetFoodDescriptionsLookup(2100)")); //wreq.ContentType = "application/json"; wreq.BeginGetResponse((cb) => { HttpWebRequest rq = cb.AsyncState as HttpWebRequest; HttpWebResponse resp = rq.EndGetResponse(cb) as HttpWebResponse; // Exception StreamReader rdr = new StreamReader(resp.GetResponseStream()); string result = rdr.ReadToEnd(); rdr.Close(); }, wreq); EDIT: While perusing SO, I noticed similar posts, like this one Why am I getting ProtocolViolationException when trying to use HttpWebRequest? and this one How do I use HttpWebRequest with GET method EDIT: The WCF 4 end point is 'adapted' from this link http://geekswithblogs.net/michelotti/archive/2010/08/21/restful-wcf-services-with-no-svc-file-and-no-config.aspx. I can use Fiddler's request builder to to construct the proper requests and changing the content type does yield the correct results.

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  • How can I distinguish between overlapping segments of text using HTML?

    - by Siracuse
    Easy question, it is valid to have overlapping spans in html? Example: <span id="1">This is <span id="2"> some text </span> some other text </span> ^ ^ End1 End2 Edit: I see now that the spans closing tag would be ambiguous about which one it is closing, and that first </span> would close span id = 2, not 1 like I intended. My problem is, I have a block of text which I'm trying to highlight based on what the mouse hovers over. This block of text is composed of sections, some of which "overlap" eachother. I'm trying to use some jQuery and HTML to present this document so when I hover over the sections, the appropriate one will be highlighted. So, in my example above, the first span is meant to be ended with the first span close tag, and the second span is meant to be ended to with the second span close tag. This is because of the semantics of my document, these are two overlapping segments. I want it so when I hover to the left, it will only highlight up to span id = 1 and the first span close, if I hover between the two "overlapping" spans, it will highlight both of them, and if I hover to the right, it will highlight from span id=2 to the last span close. However, I'm starting to think this isn't possible. Is there any way I can distinguish segments of text in HTML that allows overlapping? So my jQuery script that highlights when I hover over different spans will highlight the correct portions. Should I alternate between div's and spans? Would that disambiguate what I'm closing then and allow me the do the proper highlighting with my jQuery hover script? I'm wondering about more than 2 segments overlapping now. Sigh, I wish I could just be explicate about what I'm closing.

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  • dig works but dig +trace <domain_name> not working

    - by anoopmathew
    In my local system i can't get the proper result of dig +trace , but dig works fine. I'm using Ubuntu 10.04 LTS version. I'll attach the result of dig and dig +trace along with this updates. dig +trace gmail.com ; << DiG 9.7.0-P1 << +trace gmail.com ;; global options: +cmd ;; Received 12 bytes from 4.2.2.4#53(4.2.2.4) in 291 ms dig gmail.com ; << DiG 9.7.0-P1 << gmail.com ;; global options: +cmd ;; Got answer: ;; -HEADER<<- opcode: QUERY, status: NOERROR, id: 59528 ;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;gmail.com. IN A ;; ANSWER SECTION: gmail.com. 49 IN A 74.125.236.118 gmail.com. 49 IN A 74.125.236.117 ;; Query time: 302 msec ;; SERVER: 4.2.2.4#53(4.2.2.4) ;; WHEN: Sat Oct 13 14:57:56 2012 ;; MSG SIZE rcvd: 59 Please anyone update a solution for this issue. I'm just worried about my issue.

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  • PHP: Retrieving JSON via jQuery ajax help

    - by iamjonesy
    Hey I have a script that is creating and echoing a JSON encoded array of magento products. I have a script that calls this script using jQuery's ajax function but I'm not getting a proper response. This is the script that creates the array: $collection = Mage::getModel('catalog/product')->getCollection(); $collection->addAttributeToSelect('name'); $collection->addAttributeToSelect('price'); $products = array(); foreach ($collection as $product){ $products[$product->getPrice()] = $product->getName(); } header('Content-Type: application/x-json; charset=utf-8'); echo(json_encode($products)); Here is my jQuery: <select id="products"> <option value="#">Select</option> </select> <script type="text/javascript"> jQuery.noConflict(); jQuery(document).ready(function(){ jQuery.ajax({ type: "GET", url: "http://localhost.com/magento/modules/products/get.php", dataType: "json", success: function(products) { jQuery.each(products,function(price,name) { var opt = jQuery('<option />'); opt.val(name); opt.text(price); jQuery('#products').append(opt); }); } }); }); </script> I'm getting a response from this but I'm not seeing a any JSON. I'm using firebug. I can see there has been a JSON encoded response but the response tab is emtyp and my select boxes have no options. Can anyone see and problems with my code? Here is the response I should get: {"82.9230":"Dummy","177.0098":"Dummy 2","76.0208":"Dummy 3","470.6054":"Dummy 4","357.0083":"Dummy Product 5"} Thanks, Billy

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  • How to create extensible dynamic array in Java without using pre-made classes?

    - by AndrejaKo
    Yeah, it's a homework question, so givemetehkodezplsthx! :) Anyway, here's what I need to do: I need to have a class which will have among its attributes array of objects of another class. The proper way to do this in my opinion would be to use something like LinkedList, Vector or similar. Unfortunately, last time I did that, I got fire and brimstone from my professor, because according to his belief I was using advanced stuff without understanding basics. Now next obvious solution would be to create array with fixed number of elements and add checks to get and set which will see if the array is full. If it is full, they'd create new bigger array, copy older array's data to the new array and return the new array to the caller. If it's mostly empty, they'd create new smaller array and move data from old array to new. To me this looks a bit stupid. For my homework, there probably won't be more that 3 elements in an array, but I'd like to make a scalable solution without manually calculating statistics about how often is array filled, what is the average number of new elements added, then using results of calculation to calculate number of elements in new array and so on. By the way, there is no need to remove elements from the middle of the array. Any tips?

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  • How can I distinguish between overlapping segments of text using HTML / jQuery?

    - by Siracuse
    Easy question, it is valid to have overlapping spans in html? Example: <span id="1">This is <span id="2"> some text </span> some other text </span> ^ ^ End1 End2 Edit: I see now that the spans closing tag would be ambiguous about which one it is closing, and that first </span> would close span id = 2, not 1 like I intended. My problem is, I have a block of text which I'm trying to highlight based on what the mouse hovers over. This block of text is composed of sections, some of which "overlap" eachother. I'm trying to use some jQuery and HTML to present this document so when I hover over the sections, the appropriate one will be highlighted. So, in my example above, the first span is meant to be ended with the first span close tag, and the second span is meant to be ended to with the second span close tag. This is because of the semantics of my document, these are two overlapping segments. I want it so when I hover to the left, it will only highlight up to span id = 1 and the first span close, if I hover between the two "overlapping" spans, it will highlight both of them, and if I hover to the right, it will highlight from span id=2 to the last span close. However, I'm starting to think this isn't possible. Is there any way I can distinguish segments of text in HTML that allows overlapping? So my jQuery script that highlights when I hover over different spans will highlight the correct portions. Should I alternate between div's and spans? Would that disambiguate what I'm closing then and allow me the do the proper highlighting with my jQuery hover script? I'm wondering about more than 2 segments overlapping now. Sigh, I wish I could just be explicate about what I'm closing.

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  • How to allow one thread to mutate an array property while another thread iterates on a copy of the a

    - by Steve918
    I would like to implement an observer pattern in Objective-C where the observer implements an interface similar to SKPaymentTransactionObserver and the observable class just extends my base observable. My observable class looks something like what is below. Notice I'm making copies of the observers before enumeration to avoid throwing an exception . I've tried adding an NSLock around add observers and notify observers, but I run into a deadlock. What would be the proper way to handle concurrency when observers are being added as notifications are being sent? @implementation Observable -(void)notifyObservers:(SEL)selector { @synchronized(self) { NSSet* observer_copy = [observers copy]; for (id observer in observer_copy) { if([observer respondsToSelector: selector]) { [observer performSelector: selector]; } } [observer_copy release]; } } -(void)notifyObservers:(SEL)selector withObject:(id)arg1 withObject:(id)arg2 { @synchronized(self) { NSSet* observer_copy = [observers copy]; for (id observer in observer_copy) { if([observer respondsToSelector: selector]) { [observer performSelector: selector withObject: arg1 withObject: arg2]; } } [observer_copy release]; } } -(void)addObserver:(id)observer { @synchronized(self) { [observers addObject: observer]; } } -(void)removeObserver:(id)observer { @synchronized(self) { [observers removeObject: observer]; } }

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  • Update "Properties" model when adding a new record in CakePHP

    - by Paul Willy
    Hi, I'm writing an application in CakePHP that, for now, is to be used to make quotes for customers. So Quote is a model. I want to have a separate model/table for something like "Property," which may be used by other models. Each time a user gets to the "Add Quote" action, I basically want to pull a Property called "nextQuoteNumber" or something along those lines, and then automatically increment that property, even if the new Quote isn't saved. So I don't think just using an autoincrement for Quote's id is appropriate here - also, the "quote number" could be different from the row's id. I know this is simple enough to do, but I'm trying to figure out the "proper" CakePHP way of doing it! I'm thinking that I should have a method inside the Property model, say "getProperty($property_name)", which would pull the value to return, and also increment the value... but I'm not sure what the best way of doing that is, or how to invoke this method from the Quotes controller. What should I do? Thanks in advance!

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  • How can we serialize a class that is not a custom class of our own?

    - by Doug
    I need to look at the properties of an object and I cannot instantiate this object in the proper state on my dev machine. I need my client to run some code on her machine, serialize the object in question to disk and then I can analyze the file. Here is the class I want to serialize. System.Security.AccessControl.RegistrySecurity Here is my code: Private Sub SerializeRegSecurity(ByVal regKey As RegistryKey) Try Dim regSecurity As System.Security.AccessControl.RegistrySecurity = regKey.GetAccessControl() Dim oXS As XmlSerializer = New XmlSerializer(GetType(System.Security.AccessControl.RegistrySecurity)) Dim oStmW As StreamWriter Dim regDebugFilePath As String = Path.Combine(My.Computer.FileSystem.SpecialDirectories.Desktop, "RegDebugFile.xml") 'Serialize object to XML and write it to XML file oStmW = New StreamWriter(regDebugFilePath) oXS.Serialize(oStmW, regSecurity) oStmW.Close() Catch ex As Exception Console.WriteLine(ex.ToString) End Try End Sub And here's what I end up with in my XML file: <?xml version="1.0" encoding="utf-8"?> Any ideas on how to accomplish what I am trying to do? How can we serialize a class that is not a custom class of our own? Thanks for ANY help. Even an alternate method.

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  • What is the return type for a anonymous linq query select? What is the best way to send this data ba

    - by punkouter
    This is a basic question. I have the basic SL4/RIA project set up and I want to create a new method in the domain service and return some data from it. I am unsure the proper easiest way to do this.. Should I wrap it up in a ToList()? I am unclear how to handle this anonymous type that was create.. what is the easiest way to return this data? public IQueryable<ApplicationLog> GetApplicationLogsGrouped() { var x = from c in ObjectContext.ApplicationLogs let dt = c.LogDate group c by new { y = dt.Value.Year, m = dt.Value.Month, d = dt.Value.Day } into mygroup select new { aaa = mygroup.Key, ProductCount = mygroup.Count() }; return x; // return this.ObjectContext.ApplicationLogs.Where(r => r.ApplicationID < 50); } Cannot implicitly convert type 'System.Linq.IQueryable<AnonymousType#1>' to 'System.Linq.IQueryable<CapRep4.Web.ApplicationLog>'. An explicit conversion exists (are you missing a cast?) 58 20 CapRep4.Web

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  • Am I abusing Policies?

    - by pmr
    I find myself using policies a lot in my code and usually I'm very happy with that. But from time to time I find myself confronted with using that pattern in situations where the Policies are selected and runtime and I have developed habbits to work around such situations. Usually I start with something like that: class DrawArrays { protected: void sendDraw() const; }; class DrawElements { protected: void sendDraw() const; }; template<class Policy> class Vertices : public Policy { using Policy::sendDraw(); public: void render() const; }; When the policy is picked at runtime I have different choices of working around the situation. Different code paths: if(drawElements) { Vertices<DrawElements> vertices; } else { Vertices<DrawArrays> vertices; } Inheritance and virtual calls: class PureVertices { public: void render()=0; }; template<class Policy> class Vertices : public PureVertices, public Policy { //.. }; Both solutions feel wrong to me. The first creates an umaintainable mess and the second introduces the overhead of virtual calls that I tried to avoid by using policies in the first place. Am I missing the proper solutions or do I use the wrong pattern to solve the problem?

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  • Simple jQuery code contains a syntax error that I can't find

    - by inkedmn
    I've got this (remarkably) simple JavaScript function that is called when a user clicks a "Cancel" link: function hideNewUserPanel(){ $('#create_user_panel').slideUp('slow'); $('.right_interior_panel').slideDown('slow'); } And the code to add the handler: $(function(){ $('#cancel_create_user_btn').live('click', function(){ hideNewUserPanel(); } }); Functionally, everything works as expected. Trouble is, when I click the "Cancel" link, Firebug shows an error in the console: uncaught exception: Syntax error, unrecognized expression: # I've stepped through the code several times and the error appears at some point before the call to hideNewUserPanel(). At the risk of sounding like one of "those programmers" (the kind that claim to have found a bug in GCC and assume their own code is perfect), the exception is being thrown from somewhere within jQuery proper, so I assume the issue is in there. I'm using jQuery 1.3.2 (this is a legacy project using many jQuery plugins that will break if we update to 1.4.x). Is there anything obviously wrong with my code that I'm simply not seeing? This code is, frankly, very simple and I don't really see what the issue could be. Thanks!

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  • Password hashing, salt and storage of hashed values

    - by Jonathan Leffler
    Suppose you were at liberty to decide how hashed passwords were to be stored in a DBMS. Are there obvious weaknesses in a scheme like this one? To create the hash value stored in the DBMS, take: A value that is unique to the DBMS server instance as part of the salt, And the username as a second part of the salt, And create the concatenation of the salt with the actual password, And hash the whole string using the SHA-256 algorithm, And store the result in the DBMS. This would mean that anyone wanting to come up with a collision should have to do the work separately for each user name and each DBMS server instance separately. I'd plan to keep the actual hash mechanism somewhat flexible to allow for the use of the new NIST standard hash algorithm (SHA-3) that is still being worked on. The 'value that is unique to the DBMS server instance' need not be secret - though it wouldn't be divulged casually. The intention is to ensure that if someone uses the same password in different DBMS server instances, the recorded hashes would be different. Likewise, the user name would not be secret - just the password proper. Would there be any advantage to having the password first and the user name and 'unique value' second, or any other permutation of the three sources of data? Or what about interleaving the strings? Do I need to add (and record) a random salt value (per password) as well as the information above? (Advantage: the user can re-use a password and still, probably, get a different hash recorded in the database. Disadvantage: the salt has to be recorded. I suspect the advantage considerably outweighs the disadvantage.) There are quite a lot of related SO questions - this list is unlikely to be comprehensive: Encrypting/Hashing plain text passwords in database Secure hash and salt for PHP passwords The necessity of hiding the salt for a hash Clients-side MD5 hash with time salt Simple password encryption Salt generation and Open Source software I think that the answers to these questions support my algorithm (though if you simply use a random salt, then the 'unique value per server' and username components are less important).

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  • Passing IDisposable objects through constructor chains

    - by Matt Enright
    I've got a small hierarchy of objects that in general gets constructed from data in a Stream, but for some particular subclasses, can be synthesized from a simpler argument list. In chaining the constructors from the subclasses, I'm running into an issue with ensuring the disposal of the synthesized stream that the base class constructor needs. Its not escaped me that the use of IDisposable objects this way is possibly just dirty pool (plz advise?) for reasons I've not considered, but, this issue aside, it seems fairly straightforward (and good encapsulation). Codes: abstract class Node { protected Node (Stream raw) { // calculate/generate some base class properties } } class FilesystemNode : Node { public FilesystemNode (FileStream fs) : base (fs) { // all good here; disposing of fs not our responsibility } } class CompositeNode : Node { public CompositeNode (IEnumerable some_stuff) : base (GenerateRaw (some_stuff)) { // rogue stream from GenerateRaw now loose in the wild! } static Stream GenerateRaw (IEnumerable some_stuff) { var content = new MemoryStream (); // molest elements of some_stuff into proper format, write to stream content.Seek (0, SeekOrigin.Begin); return content; } } I realize that not disposing of a MemoryStream is not exactly a world-stopping case of bad CLR citizenship, but it still gives me the heebie-jeebies (not to mention that I may not always be using a MemoryStream for other subtypes). It's not in scope, so I can't explicitly Dispose () it later in the constructor, and adding a using statement in GenerateRaw () is self-defeating since I need the stream returned. Is there a better way to do this? Preemptive strikes: yes, the properties calculated in the Node constructor should be part of the base class, and should not be calculated by (or accessible in) the subclasses I won't require that a stream be passed into CompositeNode (its format should be irrelevant to the caller) The previous iteration had the value calculation in the base class as a separate protected method, which I then just called at the end of each subtype constructor, moved the body of GenerateRaw () into a using statement in the body of the CompositeNode constructor. But the repetition of requiring that call for each constructor and not being able to guarantee that it be run for every subtype ever (a Node is not a Node, semantically, without these properties initialized) gave me heebie-jeebies far worse than the (potential) resource leak here does.

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  • C# parameters by reference and .net garbage collection

    - by Yarko
    I have been trying to figure out the intricacies of the .NET garbage collection system and I have a question related to C# reference parameters. If I understand correctly, variables defined in a method are stored on the stack and are not affected by garbage collection. So, in this example: public class Test { public Test() { } public int DoIt() { int t = 7; Increment(ref t); return t; } private int Increment(ref int p) { p++; } } the return value of DoIt() will be 8. Since the location of t is on the stack, then that memory cannot be garbage collected or compacted and the reference variable in Increment() will always point to the proper contents of t. However, suppose we have: public class Test { private int t = 7; public Test() { } public int DoIt() { Increment(ref t); return t; } private int Increment(ref int p) { p++; } } Now, t is stored on the heap as it is a value of a specific instance of my class. Isn't this possibly a problem if I pass this value as a reference parameter? If I pass t as a reference parameter, p will point to the current location of t. However, if the garbage collector moves this object during a compact, won't that mess up the reference to t in Increment()? Or does the garbage collector update even references created by passing reference parameters? Do I have to worry about this at all? The only mention of worrying about memory being compacted on MSDN (that I can find) is in relation to passing managed references to unmanaged code. Hopefully that's because I don't have to worry about any managed references in managed code. :)

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  • Database nesting layout confusion

    - by arzon
    I'm no expert in databases and a beginner in Rails, so here goes something which kinda confuses me... Assuming I have three classes as a sample (note that no effort has been made to address any possible Rails reserved words issue in the sample). class File < ActiveRecord::Base has_many :records, :dependent => :destroy accepts_nested_attributes_for :records, :allow_destroy => true end class Record < ActiveRecord::Base belongs_to :file has_many :users, :dependent => :destroy accepts_nested_attributes_for :users, :allow_destroy => true end class User < ActiveRecord::Base belongs_to :record end Upon entering records, the database contents will appear as such. My issue is that if there are a lot of Files for the same Record, there will be duplicate record names. This will also be true if there will be multiple Records for the same user in the the Users table. I was wondering if there is a better way than this so as to have one or more files point to a single Record entry and one or more Records will point to a single User. BTW, the File names are unique. Files table: id name 1 name1 2 name2 3 name3 4 name4 Records table: id file_id record_name record_type 1 1 ForDaisy1 ... 2 2 ForDonald1 ... 3 3 ForDonald2 ... 4 4 ForDaisy1 ... Users table: id record_id username 1 1 Daisy 2 2 Donald 3 3 Donald 4 4 Daisy Is there any way to optimize the database to prevent duplication of entries, or this should really the correct and proper behavior. I spread out the database into different tables to be able to easily add new columns in the future.

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  • Dynamcally resizing an open Accordion

    - by alavers
    I have an Accordion and the height of its content can be dynamically resized. I would like to see the Accordion dynamically respond to the child item's height, but I'm having trouble doing this. <lt:Accordion Name="MyAccordion" SelectionMode="ZeroOrOne" HorizontalAlignment="Stretch"> <lt:AccordionItem Name="MyAccordionItem" Header="MyAccordion" IsSelected="True" HorizontalContentAlignment="Stretch" VerticalAlignment="Stretch"> <StackPanel> <Button Content="Grow" Click="Grow"/> <Button Content="Shrink" Click="Shrink"/> <TextBox Name="GrowTextBox" Text="GrowTextBox" Height="400" Background="Green" SizeChanged="GrowTextBox_SizeChanged"/> </StackPanel> </lt:AccordionItem> </lt:Accordion> private void Grow(object sender, System.Windows.RoutedEventArgs e) { GrowTextBox.Height += 100; } private void Shrink(object sender, System.Windows.RoutedEventArgs e) { GrowTextBox.Height -= 100; } private void GrowTextBox_SizeChanged(object sender, System.Windows.SizeChangedEventArgs e) { MyAccordion.UpdateLayout(); MyAccordionItem.UpdateLayout(); } Mind you, if I collapse and then re-open the accordion, it takes shape just the way I want, but I'd like this resizing to occur immediately when the child resizes. I feebly attempted to fix this by adding a SizeChanged event handler that calls UpdateLayout() on the Accordion and AccordionItem, but this doesn't have any visual effect. I can't figure out where proper resizing takes place inside the Accordion control. Does anyone have an idea?

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  • Python: circular imports needed for type checking

    - by phild
    First of all: I do know that there are already many questions and answers to the topic of the circular imports. The answer is more or less: "Design your Module/Class structure properly and you will not need circular imports". That is true. I tried very hard to make a proper design for my current project, I in my opinion I was successful with this. But my specific problem is the following: I need a type check in a module that is already imported by the module containing the class to check against. But this throws an import error. Like so: foo.py: from bar import Bar class Foo(object): def __init__(self): self.__bar = Bar(self) bar.py: from foo import Foo class Bar(object): def __init__(self, arg_instance_of_foo): if not isinstance(arg_instance_of_foo, Foo): raise TypeError() Solution 1: If I modified it to check the type by a string comparison, it will work. But I dont really like this solution (string comparsion is rather expensive for a simple type check, and could get a problem when it comes to refactoring). bar_modified.py: from foo import Foo class Bar(object): def __init__(self, arg_instance_of_foo): if not arg_instance_of_foo.__class__.__name__ == "Foo": raise TypeError() Solution 2: I could also pack the two classes into one module. But my project has lots of different classes like the "Bar" example, and I want to seperate them into different module files. After my own 2 solutions are no option for me: Has anyone a nicer solution for this problem?

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  • Passing Derived Class Instances as void* to Generic Callbacks in C++

    - by Matthew Iselin
    This is a bit of an involved problem, so I'll do the best I can to explain what's going on. If I miss something, please tell me so I can clarify. We have a callback system where on one side a module or application provides a "Service" and clients can perform actions with this Service (A very rudimentary IPC, basically). For future reference let's say we have some definitions like so: typedef int (*callback)(void*); // This is NOT in our code, but makes explaining easier. installCallback(string serviceName, callback cb); // Really handled by a proper management system sendMessage(string serviceName, void* arg); // arg = value to pass to callback This works fine for basic types such as structs or builtins. We have an MI structure a bit like this: Device <- Disk <- MyDiskProvider class Disk : public virtual Device class MyDiskProvider : public Disk The provider may be anything from a hardware driver to a bit of glue that handles disk images. The point is that classes inherit Disk. We have a "service" which is to be notified of all new Disks in the system, and this is where things unravel: void diskHandler(void *p) { Disk *pDisk = reinterpret_cast<Disk*>(p); // Uh oh! // Remainder is not important } SomeDiskProvider::initialise() { // Probe hardware, whatever... // Tell the disk system we're here! sendMessage("disk-handler", reinterpret_cast<void*>(this)); // Uh oh! } The problem is, SomeDiskProvider inherits Disk, but the callback handler can't receive that type (as the callback function pointer must be generic). Could RTTI and templates help here? Any suggestions would be greatly appreciated.

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  • Any info about book "Unix Internals: The New Frontiers" by Uresh Vahalia 2nd edition (Jan 2010)

    - by claws
    This summer I'm getting into UNIX (mostly *BSD) development. I've graduate level knowledge about operating systems. I can also understand the code & read from here and there but the thing is I want to make most of my time. Reading books are best for this. From my search I found that these two books The Design and Implementation of the 4.4 BSD Operating System "Unix Internals: The New Frontiers" by Uresh Vahalia are like established books on UNIX OS internals. But the thing is these books are pretty much outdated. yay!! Lucky me. "Unix Internals: The New Frontiers" by Uresh Vahalia 2 edition (Jan 2010) is released. I've been search for information on this book. Sadly, Amazon says "Out of Print--Limited Availability" & I couldn't find any info regarding this book. This is the information I'm looking for: Table of Contents Whats new in this edition? Where the hell can I buy soft-copy of this book? I really cannot afford buying a hardcopy. How can I contact the author? I've lot of hopes & expectations on this book. I've been waiting for its release for a long time. I've sent random mails to & & requesting to have a proper website for this book. I even contacted publisher for any further information but no replies from any one. If you have any other books that you think will help me. I again repeat, I want to get max possible out of these 2.5 months summer.

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