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  • How do I manipulate a tree of immutable objects?

    - by Frederik
    I'm building an entire application out of immutable objects so that multi-threading and undo become easier to implement. I'm using the Google Collections Library which provides immutable versions of Map, List, and Set. My application model looks like a tree: Scene is a top-level object that contains a reference to a root Node. Each Node can contain child Nodes and Ports. An object graph might look like this: Scene | +-- Node | +-- Node | +- Port +-- Node | +- Port +- Port If all of these objects are immutable, controlled by a top-level SceneController object: What is the best way to construct this hierarchy? How would I replace an object that is arbitrarily deep in the object tree? Is there a way to support back-links, e.g. a Node having a "parent" attribute?

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  • How do I use a custom select statement in Hibernate using the HibernateDaoSupport class

    - by Bill Leeper
    I am trying to write a custom select statement in Hibernate using the getHibernateTemplate() method. I am having problems with the resulting mapping. Example Code: List<User> users = getHibernateTemplate().find("Select user, sysdate as latestPost from User as user"); for (User user : users) { assertNotNull(users.name); } The goal of the above line is to eventually have a join where I get the max(date) of posts made by the user. The problem I am having is that the resulting users list is not a list of User objects and I get a class cast exception. Hopefully that is enough code. It is a greatly simplified version of my problem and a combination of snippets from various parts of my application.

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  • how can protected members of base class be accessed during unit test?

    - by amateur
    I am creating a unit test in mstest with rhino mocks. I have a class A that inherits class B. I am testing class A and create an instance of it for my test. The class it inherits, "B", has some protected methods and protected properties that I would like to access for the benefit of my tests. For example, validate that a protected property on my base class has the expected value. Any ideas how I might access these protected properties of class B during my test?

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  • benefit os having a factory for object creation?

    - by ajsie
    im trying to understand the factory design pattern. i dont understand why it's good to have a middleman between the client and the product (object that the client wants). example with no factory: $mac = new Mac(); example with a factory: $appleStore = new AppleStore(); $mac = $appleStore->getProduct('mac'); how does the factory pattern decouple the client from the product? could someone give an example of a future code change that will impact on example 1 negative, but positive in example 2 so i understand the importance of decoupling? thanks

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  • Delete on a very deep tree

    - by Kathoz
    I am building a suffix trie (unfortunately, no time to properly implement a suffix tree) for a 10 character set. The strings I wish to parse are going to be rather long (up to 1M characters). The tree is constructed without any problems, however, I run into some when I try to free the memory after being done with it. In particularly, if I set up my constructor and destructor to be as such (where CNode.child is a pointer to an array of 10 pointers to other CNodes, and count is a simple unsigned int): CNode::CNode(){ count = 0; child = new CNode* [10]; memset(child, 0, sizeof(CNode*) * 10); } CNode::~CNode(){ for (int i=0; i<10; i++) delete child[i]; } I get a stack overflow when trying to delete the root node. I might be wrong, but I am fairly certain that this is due to too many destructor calls (each destructor calls up to 10 other destructors). I know this is suboptimal both space, and time-wise, however, this is supposed to be a quick-and-dirty solution to a the repeated substring problem. tl;dr: how would one go about freeing the memory occupied by a very deep tree? Thank you for your time.

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  • Class properties vs NSArray / NSDictionary

    - by Frank Martin
    I want a custom class object to hold data and have somehow the feeling that creating about 80 properties is not the best way of doing it. Most of the properties would be bool values, so i'm thinking about creating Arrays (keys / values) or (probably better) a NSDictionary attached to the object for holding the data. Does that make sense or should i stay with the properties? Extra: Are there general pros and cons for the different approaches? And what keywords / concepts do i have to search for to find discussions about that somehow general question? Thanks in advance

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  • Scanner class is skipping lines

    - by user2403304
    I'm new to programing and I'm having a problem with my scanner class. This code is in a loop and when the loop comes around the second, third whatever time I have it set to it skips the first title input. I need help please why is it skipping my title scanner input in the beginning? System.out.println("Title:"); list[i].title=keyboard.nextLine(); System.out.println("Author:"); list[i].author=keyboard.nextLine(); System.out.println("Album:"); list[i].album=keyboard.nextLine(); System.out.println("Filename:"); list[i].filename=keyboard.nextLine();

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  • Problem in reading configuration file from Class library project

    - by Newbie
    If I create an app.config file in a console apps like this <?xml version="1.0" encoding="utf-8" ?> <configuration> <appSettings> <add key ="key1" value ="val1"/> </appSettings> </configuration> and access the same from the console application like object sourcePath = System.Configuration.ConfigurationManager.AppSettings["key1"]; or by object sourcePath = System.Configuration.ConfigurationSettings.AppSettings["key1"]; I am able to get the value. But if I do the same thing in a class library project, I am getting a null value. Why? Where I am making mistake? I have added the proper reference System.Configuration. I am using C# 3.0

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  • class classname(value); & class classname=value; difference when constructor is explicit

    - by Mahesh
    When constructor is explicit, it isn't used for implicit conversions. In the given snippet, constructor is marked as explicit. Then why in case foo obj1(10.25); it is working and in foo obj2=10.25; it isn't working ? #include <iostream> class foo { int x; public: explicit foo( int x ):x(x) {} }; int main() { foo obj(10.25); // Not an error. Why ? foo obj2 = 10.25; // Error getchar(); return 0; } error: error C2440: 'initializing' : cannot convert from 'double' to 'foo'

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  • Why and How to avoid Event Handler memory leaks ?

    - by gillyb
    Hey There, I just came to realize, by reading some questions and answers on StackOverflow, that adding event handlers using += in C# (or i guess, other .net languages) can cause common memory leaks... I have used event handlers like this in the past many times, and never realized that they can cause, or have caused, memory leaks in my applications. How does this work (meaning, why does this actually cause a memory leak) ? How can I fix this problem ? Is using -= to the same event handler enough ? Are there common design patterns or best practices for handling situations like this ? Example : How am I supposed to handle an application that has many different threads, using many different event handlers to raise several events on the UI ? Are there any good and simple ways to monitor this efficiently in an already built big application ? Thanks in advance!

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  • Sequencing ajax requests

    - by Scott Evernden
    I find I sometimes need to iterate some collection and make an ajax call for each element. I want each call to return before moving to the next element so that I don't blast the server with requests - which often leads to other issues. And I don't want to set async to false and freeze the browser. Usually this involves setting up some kind of iterator context that i step thru upon each success callback. I think there must be a cleaner simpler way? Does anyone have a clever design pattern for how to neatly work thru a collection making ajax calls for each item?

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  • PHP - Class Inherit problem

    - by TatMing
    I have A.php and B.php A.php <?php error_reporting(E_ALL); ini_set("display_errors",1); class myClass { function hello() { return 'hello'; } } ?> B.php <?php error_reporting(E_ALL); ini_set("display_errors",1); require_once('/A.php'); $a = new myClass(); testing(); function testing() { echo $a ->hello(); } ?> B.php inherits A.php , if i run B.php,but it show "Fatal error: Call to a member function hello() on a non-object." So the question is simple, how can i correct this ,but "$a = new myClass();" is not inside the function, since in .NET world can do this, i believe PHP also possible. And one more question is, what is the modify of function in A.php ,if i have not state private/public/protected???

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  • How to implement copy operator for such C++ structure?

    - by Kabumbus
    So having struct ResultStructure { ResultStructure(const ResultStructure& other) { // copy code in here ? using memcpy ? how??? } ResultStructure& operator=(const ResultStructure& other) { if (this != &other) { // copy code in here ? } return *this } int length; char* ptr; }; How to implement copy? (sorry - I am C++ nube)

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  • How should nested components interact with model in a GUI application?

    - by fig-gnuton
    Broad design/architecture question. If you have nested components in a GUI, what's the most common way for those components to interact with data? For example, let's say a component receives a click on one of its buttons to save data. Should the save request be delegated up that component's ancestors, with the uppermost ancestor ultimately passing the request to a controller? Or are models/datastores in a GUI application typically singletons, so that a component at any level of a hierarchy can directly get/set data? Or is a controller injected as a dependency down the hierarchy of components, so that any given component is only one intermediary away from the datastore/model?

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  • changing body class based on user's local time

    - by John
    I'm trying to add a body class of 'day' if it's 6am-5pm and 'night' if "else" based on the user's local time. I tried the following but it didn't work. Any ideas? In the head: <script> function setTimesStyles() { var currentTime = new Date().getHours(); if(currentTime > 5 && currentTime < 17) { document.body.className = 'day'; } else { document.body.className = 'night'; } } </script> In the body: <body onload="setTimeStyles();"> Also, is there a more elegant way to achieve what I need?

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  • C++ function will not return

    - by Mike
    I have a function that I am calling that runs all the way up to where it should return but doesn't return. If I cout something for debugging at the very end of the function, it gets displayed but the function does not return. fetchData is the function I am referring to. It gets called by outputFile. cout displays "done here" but not "data fetched" I know this code is messy but can anyone help me figure this out? Thanks //Given an inode return all data of i_block data char* fetchData(iNode tempInode){ char* data; data = new char[tempInode.i_size]; this->currentInodeSize = tempInode.i_size; //Loop through blocks to retrieve data vector<unsigned int> i_blocks; i_blocks.reserve(tempInode.i_blocks); this->currentDataPosition = 0; cout << "currentDataPosition set to 0" << std::endl; cout << "i_blocks:" << tempInode.i_blocks << std::endl; int i = 0; for(i = 0; i < 12; i++){ if(tempInode.i_block[i] == 0) break; i_blocks.push_back(tempInode.i_block[i]); } appendIndirectData(tempInode.i_block[12], &i_blocks); appendDoubleIndirectData(tempInode.i_block[13], &i_blocks); appendTripleIndirectData(tempInode.i_block[14], &i_blocks); //Loop through all the block addresses to get the actual data for(i=0; i < i_blocks.size(); i++){ appendData(i_blocks[i], data); } cout << "done here" << std::endl; return data; } void appendData(int block, char* data){ char* tempBuffer; tempBuffer = new char[this->blockSize]; ifstream file (this->filename, std::ios::binary); int entryLocation = block*this->blockSize; file.seekg (entryLocation, ios::beg); file.read(tempBuffer, this->blockSize); //Append this block to data for(int i=0; i < this->blockSize; i++){ data[this->currentDataPosition] = tempBuffer[i]; this->currentDataPosition++; } data[this->currentDataPosition] = '\0'; } void outputFile(iNode file, string filename){ char* data; cout << "File Transfer Started" << std::endl; data = this->fetchData(file); cout << "data fetched" << std::endl; char *outputFile = (char*)filename.c_str(); ofstream myfile; myfile.open (outputFile,ios::out|ios::binary); int i = 0; for(i=0; i < file.i_size; i++){ myfile << data[i]; } myfile.close(); cout << "File Transfer Completed" << std::endl; return; }

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  • Add another class to a div with javascript

    - by zac
    I have a function that checks the age of a form submission and then returns new content in a div depending on their age. right now I am just using getElementById to replace the html content. BUt I think would work better for me if I could also add a class to a div as well. So for example I have.. if (under certain age) { document.getElementById('hello').innerHTML = "<p>Good Bye</p>"; createCookie('age','not13',0) return false; } else { document.getElementById('hello').innerHTML = "<p>Hello</p>"; return true; } What I would like to do is have everything in a div and if return false then that div disappears and is replaced with other content.. can I get any ideas on a good way to achieve this with pure javascript. I dont want to use jQuery for this particular function.

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  • building an XML service parsing library

    - by DanInDC
    This is more of a design question I suppose. My company offers a web service to our client that spits data out in a custom xml format. I'd like to build a java library we can offer so our customers can just feed it the url and we will turn it into a set of POJOs built from the response. I can obviously just create a library that will do some simple xml parsing and building of the POJOs but I'm looking to build something a bit more robust. My brain is pulling me in a million directions, wondering if anyone has some pointers or some code to poke at. Was thinking about adding an Abdera extension, but it's not really a syndication format that fits the Abdera model. And most of the popular service libraries (twitter, facebook) all rely on standards format parsers, of which our format isn't.

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  • How to model a relationship that NHibernate (or Hibernate) doesn’t easily support

    - by MylesRip
    I have a situation in which the ideal relationship, I believe, would involve Value Object Inheritance. This is unfortunately not supported in NHibernate so any solution I come up with will be less than perfect. Let’s say that: “Item” entities have a “Location” that can be in one of multiple different formats. These formats are completely different with no overlapping fields. We will deal with each Location in the format that is provided in the data with no attempt to convert from one format to another. Each Item has exactly one Location. “SpecialItem” is a subtype of Item, however, that is unique in that it has exactly two Locations. “Group” entities aggregate Items. “LocationGroup” is as subtype of Group. LocationGroup also has a single Location that can be in any of the formats as described above. Although I’m interested in Items by Group, I’m also interested in being able to find all items with the same Location, regardless of which group they are in. I apologize for the number of stipulations listed above, but I’m afraid that simplifying it any further wouldn’t really reflect the difficulties of the situation. Here is how the above could be diagrammed: Mapping Dilemma Diagram: (http://www.freeimagehosting.net/uploads/592ad48b1a.jpg) (I tried placing the diagram inline, but Stack Overflow won't allow that until I have accumulated more points. I understand the reasoning behind it, but it is a bit inconvenient for now.) Hmmm... Apparently I can't have multiple links either. :-( Analyzing the above, I make the following observations: I treat Locations polymorphically, referring to the supertype rather than the subtype. Logically, Locations should be “Value Objects” rather than entities since it is meaningless to differentiate between two Location objects that have all the same values. Thus equality between Locations should be based on field comparisons, not identifiers. Also, value objects should be immutable and shared references should not be allowed. Using NHibernate (or Hibernate) one would typically map value objects using the “component” keyword which would cause the fields of the class to be mapped directly into the database table that represents the containing class. Put another way, there would not be a separate “Locations” table in the database (and Locations would therefore have no identifiers). NHibernate (or Hibernate) do not currently support inheritance for value objects. My choices as I see them are: Ignore the fact that Locations should be value objects and map them as entities. This would take care of the inheritance mapping issues since NHibernate supports entity inheritance. The downside is that I then have to deal with aliasing issues. (Meaning that if multiple objects share a reference to the same Location, then changing values for one object’s Location would cause the location to change for other objects that share the reference the same Location record.) I want to avoid this if possible. Another downside is that entities are typically compared by their IDs. This would mean that two Location objects would be considered not equal even if the values of all their fields are the same. This would be invalid and unacceptable from the business perspective. Flatten Locations into a single class so that there are no longer inheritance relationships for Locations. This would allow Locations to be treated as value objects which could easily be handled by using “component” mapping in NHibernate. The downside in this case would be that the domain model becomes weaker, more fragile and less maintainable. Do some “creative” mapping in the hbm files in order to force Location fields to be mapped into the containing entities’ tables without using the “component” keyword. This approach is described by Colin Jack here. My situation is more complicated than the one he describes due to the fact that SpecialItem has a second Location and the fact that a different entity, LocatedGroup, also has Locations. I could probably get it to work, but the mappings would be non-intuitive and therefore hard to understand and maintain by other developers in the future. Also, I suspect that these tricky mappings would likely not be possible using Fluent NHibernate so I would use the advantages of using that tool, at least in that situation. Surely others out there have run into similar situations. I’m hoping someone who has “been there, done that” can share some wisdom. :-) So here’s the question… Which approach should be preferred in this situation? Why?

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  • What is/are the Scala way(s) to implement this Java "byte[] to Hex" class

    - by nicerobot
    I'm specifically interested in Scala (2.8) techniques for building strings with formats as well as interesting ways to make such a capability easily accessible where it's useful (lists of bytes, String, ...?).. public class Hex { public static String valueOf (final byte buf[]) { if (null == buf) { return null; } final StringBuilder sb = new StringBuilder(buf.length * 2); for (final byte b : buf) { sb.append(String.format("%02X", b & 0xff)); } return sb.toString(); } public static String valueOf (final Byteable o) { return valueOf(o.toByteArray()); } } This is only a learning exercise (so the utility and implementation of the Java isn't a concern.) Thanks

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  • Dynamically create Javascript object and give class

    - by George
    I'm dynamically creating option elements for a drop down menu using Javascript and would like to know how to add a class to them so that I can style them with CSS. I have the following code: for (var i=0;i<portfolio.length-1;i++) { portfolioSelect.options[portfolioSelect.options.length] = new Option(portfolio[i]); } where portfolio is an array populated by an outside source. HTML where options inserted: <select id="portfolio" name="portfolio"> <option selected="selected" value="Select One">Select One</option> </select>

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