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  • Can a problem have a relation of aggregation and composition both between two classes at same point

    - by learner
    Can a problem have a relation of aggregation and composition both between two classes at same point of time? Like any real time scenario where there can be aggregation corresponding to one method and composition related to other method. I m unable to figure out any scenario where both composition and aggregation occurs simultaneously between two classes. Any help will be appreciable.

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  • C#: Specify that a function arg must inhert from one class, and implement an interface?

    - by Rosarch
    I'm making a game where each Actor is represented by a GameObjectController. Game Objects that can partake in combat implement ICombatant. How can I specify that arguments to a combat function must inherit from GameObjectController and implement ICombatant? Or does this indicate that my code is structured poorly? public void ComputeAttackUpdate(ICombatant attacker, AttackType attackType, ICombatant victim) In the above code, I want attacker and victim to inherit from GameObjectController and implement ICombatant. Is this syntactically possible?

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  • When to Use Properties & When to Use Methods?

    - by DaveDev
    Hi Guys I was looking at the following line of code foreach (PropertyInfo prop in t.GetProperties()) and I noticed that tprovides a method to return the type's properties instead of a property like t.Properties This makes me wonder why sometimes people use properties to make a type's data avilable and other times there's a method provided? Is there some logic behind the decision? Thanks Dave

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  • Are there any "gotchas" to watch for in using a Class (object) within itself?

    - by Clay Nichols
    I've got a Registry class and there are a few Registry values that I want to access from within that Registry class. (There is a bit of a calculation with these values so I thought I'd just put all that code right in the Registry Class itself). So we might have something within our RegistryRoutine.cls like: Function GetMyValue() as integer Dim R as new RegistryRoutine <calculations> GetMyValue=R.GetRegisetryValue (HKEY, key, value, etc.) End Function

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  • Elegant ways to print out a bunch of instance attributes in python 2.6?

    - by wds
    First some background. I'm parsing a simple file format, and wish to re-use the results in python code later, so I made a very simple class hierarchy and wrote the parser to construct objects from the original records in the text files I'm working from. At the same time I'd like to load the data into a legacy database, the loader files for which take a simple tab-separated format. The most straightforward way would be to just do something like: print "%s\t%s\t....".format(record.id, record.attr1, len(record.attr1), ...) Because there are so many columns to print out though, I thought I'd use the Template class to make it a bit easier to see what's what, i.e.: templ = Template("$id\t$attr1\t$attr1_len\t...") And I figured I could just use the record in place of the map used by a substitute call, with some additional keywords for derived values: print templ.substitute(record, attr1_len=len(record.attr1), ...) Unfortunately this fails, complaining that the record instance does not have an attribute __getitem__. So my question is twofold: do I need to implement __getitem__ and if so how? is there a more elegant way for something like this where you just need to output a bunch of attributes you already know the name for?

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  • Any method to denote object assignment?

    - by Droogans
    I've been studying magic methods in Python, and have been wondering if there's a way to outline the specific action of: a = MyClass(*params).method() versus: MyClass(*params).method() In the sense that, perhaps, I may want to return a list that has been split on the '\n' character, versus dumping the raw list into the variable a that keeps the '\n' intact. Is there a way to ask Python if its next action is about to return a value to a variable, and change action, if that's the case? I was thinking: class MyClass(object): def __init__(*params): self.end = self.method(*params) def __asgn__(self): return self.method(*params).split('\n') def __str__(self): """this is the fallback if __asgn__ is not called""" return self.method(*params)

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  • Possible to add hook as android fetches XML-strings?

    - by user247245
    I'm on my first week with android and would appreciate any insight if it's possible to hook or override the default behaviour when an android application reads their values from the resource-files to the shown layouts. What I want is to over time be able to add new/updated strings OTA and store locally and then on launch of application load new values instead of the ones in the default /res. Ideally i guess, would be an override of setContentView. Files holding updates will be in same xml-format as those in /res. (Please, no advices in other ways to do this. Just need to know if it's at all possible, without hacking the SDK) regards, /t

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  • One-to-One relation classes

    - by SeyZ
    I want to have a class named ProjectDirectory and a class named MetaDirectory. Each project has a MetaDirectory which contains some meta data. Is it the good way to write the classes like this: class ProjectDirectory(object): def __init__(self, directory=None): self.directory = directory self.meta_directory = MetaDirectory(self) def __repr__(self): return self.directory class MetaDirectory(object): def __init__(self, project_directory=None): self.project_directory = project_directory self.directory = "%s/.meta/" % project_directory ProjectDirectory has a reference to MetaDirectory and MetaDirectory has a reference to ProjectDirectory. Is there an other solution or this solution is good ?

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  • Running a loop (such as one for a mock webserver) within a thread

    - by bob c
    I'm trying to run a mock webserver within a thread within a class. I've tried passing the class' @server property to the thread block but as soon as I try to do server.accept the thread stops. Is there some way to make this work? I want to basically be able to run a webserver off of this script while still taking user input via stdin.gets. Is this possible? class Server def initialize() @server = TCPServer.new(8080) end def run() @thread = Thread.new(@server) { |server| while true newsock = server.accept puts "some stuff after accept!" next if !newsock # some other stuff end } end end def processCommand() # some user commands here end test = Server.new while true do processCommand(STDIN.gets) end In the above sample, the thread dies on server.accept

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  • Upcasting in C#: Making a Fruit a Pear

    - by Adam Kane
    Why can't I upcast (?) a Fruit to a Pear? public static class PearGenerator { public static Pear CreatePear () { // Make a new generic fruit. Fruit genericFruit = new Fruit(); // Upcast it to a pear. (Throws exception: Can't cast a Fruit to a Pear.) Pear pear = (Pear)genericFruit; // Return freshly grown pear. return ( pear ); } } public class Fruit { // some code } public class Pear : Fruit { public void PutInPie () { // some code } } Thanks!

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  • Javascript: Inherit method from base class and return the subclass's private variable

    - by marisbest2
    I have the following BaseClass defined: function BaseClass (arg1,arg2,arg3) { //constructor code here then - var privateVar = 7500; this.getPrivateVar = function() { return privateVar; }; } I want to have the following subclass which allows changing privateVar like so: function SubClass (arg1,arg2,arg3,privateVar) { //constructor code here then - var privateVar = privateVar; } SubClass.prototype = new BaseClass(); Now I want SubClass to inherit the getPrivateVar method. However, when I try this, it always returns 7500 which is the value in the BaseClass and not the value of privateVar. In other words, is it possible to inherit a BaseClass's public methods but have any references in them refer to the SubClass's properties? And how would I do that?

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  • Why this doesnt't work in C++?

    - by user3377450
    I'm doing something and I have this: //main.cpp file template<typename t1, typename t2> std::ostream& operator<<(std::ostream& os, const std::pair<t1, t2>& pair) { return os << "< " << pair.first << " , " << pair.second << " >"; } int main() { std::map<int, int> map = { { 1, 2 }, { 2, 3 } }; std::cout << *map.begin() << std::endl;//This works std::copy(map.begin(), map.end(), std::ostream_iterator<std::pair<int,int> >(std::cout, " "));//this doesn't work } I guess this is not working because in the std::copy algorithm the operator isn't defined, but what can I do?

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  • why can not create instance from any class out side of constructor?

    - by Phsika
    why i generate instance outside of class. i give inheritance snifC to sinifD i need to create instance sinifC sinifc= new sinifC() in SinifD out side of constructor? public class sinifC { public void method3() { Console.WriteLine("Deneme3"); } } public class sinifD : sinifC { void method4() { Console.WriteLine("Deneme4"); } public sinifD() { sinifC sinifc = new sinifC(); sinifc.method3(); } } i want to make it below: public class sinifC { public void method3() { Console.WriteLine("Deneme3"); } } public class sinifD : sinifC { void method4() { Console.WriteLine("Deneme4"); } sinifC sinifc = new sinifC(); sinifc.method3(); } Error: Invalid token '(' in class, struct, or interface member declaration

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  • Java : Using parent class method to access child class variable

    - by Jayant
    I have the following scenario : public class A { private int x = 5; public void print() { System.out.println(x); } } public class B extends A { private int x = 10; /*public void print() { System.out.println(x); }*/ public static void main(String[] args) { B b = new B(); b.print(); } } On executing the code, the output is : 5. How to access the child class(B's) variable(x) via the parent class method? Could this be done without overriding the print() method (i.e. uncommenting it in B)? [This is important because on overriding we will have to rewrite the whole code for the print() method again]

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  • AS3 - Can I know if a class implements an interface (or is a subclass of another class) ?

    - by lk
    With this code function someFunction(classParam:Class):Boolean { // how to know if classParam implements some interface? } i.e. Comparing classParam with IEventDispatcher interface: someFunction(EventDispatcher) // returns true someFunction(Object) // returns false I know it can't be done with is operator. But, is there a way to do it? Is there a way to know if a class implements some interface? (or is a subclass of another class?)

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  • Property and Encapsulation

    - by Lijo
    Hi Team, Following is a question regarding using Properties in class. I am software engineer with 3 years of experience. I have been using public properties instead of exposing member variables publically. Many a people told that this approach helps in encapsulation. I don’t realize any encapsulation advantage by making it a property. While discussions, I came to know that not many people knows about the real reason for going for Property. They just do it as part of coding standard. Can someone clearly explain how Property is better than public member variable? How it improves encapsulation? Thanks Lijo

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  • Is it best to make fewer calls to the database and output the results in an array?

    - by Jonathan
    I'm trying to create a more succinct way to make hundreds of db calls. Instead of writing the whole query out every time I wanted to output a single field, I tried to port the code into a class that did all the query work. This is the class I have so far: class Listing { /* Connect to the database */ private $mysql; function __construct() { $this->mysql = new mysqli(DB_LOC, DB_USER, DB_PASS, DB) or die('Could not connect'); } function getListingInfo($l_id = "", $category = "", $subcategory = "", $username = "", $status = "active") { $condition = "`status` = '$status'"; if (!empty($l_id)) $condition .= "AND `L_ID` = '$l_id'"; if (!empty($category)) $condition .= "AND `category` = '$category'"; if (!empty($subcategory)) $condition .= "AND `subcategory` = '$subcategory'"; if (!empty($username)) $condition .= "AND `username` = '$username'"; $result = $this->mysql->query("SELECT * FROM listing WHERE $condition") or die('Error fetching values'); $info = $result->fetch_object() or die('Could not create object'); return $info; } } This makes it easy to access any info I want from a single row. $listing = new Listing; echo $listing->getListingInfo('','Books')->title; This outputs the title of the first listing in the category "Books". But if I want to output the price of that listing, I have to make another call to getListingInfo(). This makes another query on the db and again returns only the first row. This is much more succinct than writing the entire query each time, but I feel like I may be calling the db too often. Is there a better way to output the data from my class and still be succinct in accessing it (maybe outputting all the rows to an array and returning the array)? If yes, How?

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  • why can not see my method if i implamented interface to normal class?

    - by Phsika
    i can not see MyLoad.TreeLoader(.... but why i can not see? i implemented iloader to TreeViewLoad. i should see TreeLoader why? namespace Rekursive { public partial class Form1 : Form { public Form1() { InitializeComponent(); } private void Form1_Load(object sender, EventArgs e) { //treeView1.Nodes.Add("Test"); iloader MyLoad = new TreeViewLoad(); MyLoad.loader("test", treeView1, 1); // i can not see MyLoad.TreeLoader(.... but why i can not see? // i implemented iloader to TreeViewLoad. i should see TreeLoader why? //TreeViewLoad myloader = new TreeViewLoad(); } } interface iloader { void loader(string nodeName, TreeView myTre, int id); } class TreeViewLoad : iloader { public void TreeLoader(TreeView tre) { // i will call loader... } public void loader(string nodeName, TreeView myTre, int id) { myTre.Nodes.Add(nodeName + id.ToString()); if (id

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  • access a property via string with array in php?

    - by sprugman
    (This is in drupal, but I don't really think that matters.) I have a big list of properties that I need to map between two objects, and in one, the value that I need to map is buried inside an array. I'm hoping to avoid hard-coding the property names in the code. If I have a class like this: class Product { public $colors, $sizes; } I can access the properties like this: $props = array('colors', 'sizes'); foreach ($props as $p) { $this->$p = $other_object->$p; } As far as I can tell, if each of the properties on the left are an array, I can't do this: foreach ($props as $p) { $this->$p[0]['value'] = $other_object->$p; } Is that correct, or am I missing some clever way around this?

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