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  • Class members allocation on heap/stack? C++

    - by simplebutperfect
    If a class is declared as follows: class MyClass { char * MyMember; MyClass() { MyMember = new char[250]; } ~MyClass() { delete[] MyMember; } }; And it could be done like this: class MyClass { char MyMember[250]; }; How does a class gets allocated on heap, like if i do MyClass * Mine = new MyClass(); Does the allocated memory also allocates the 250 bytes in the second example along with the class instantiation? And will the member be valid for the whole lifetime of MyClass object? As for the first example, is it practical to allocate class members on heap?

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  • Declaring interface in the same file as the base class, is it a good practice?

    - by Louis Rhys
    To be interchangable and testable, normally services with logic needs to have interface, e.g. public class FooService: IFooService { ... } Design-wise, I agree with this, but one of the things that bothers me with this approach is that for one service you will need to declare two things (the class and the interface), and in our team, normally two files (one for the class and one for the interface). Another discomfort is the difficulty in navigation because using "Go to definition" in IDE (VS2010) will point to the interface (since other classes refer to the interface), not the actual class. I was thinking that writing IFooService in the same file as FooService will reduce the above weirdness. After all, IFooService and FooService are very related. Is this a good practice? Is there a good reason that IFooService must be located in its own file?

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  • Is there anything wrong with my Factory class?

    - by Alex
    class PieceFactory { @SuppressWarnings("rawtypes") public Piece createPiece(String pieceType) throws Throwable{ Class pieceClass = Class.forName(pieceType); Piece piece = (Piece) pieceClass.newInstance(); return piece; } } I'm not all used to handling exceptions yet therefore I'm just throwing them, but everywhere I use a method that uses this factory it tells me I have to throw exceptions like throwable. For example, in one of my classes I have a method that instantiates a lot of objects using the method that uses the factory. I can use the method in that class by just throwing the exception, however it won't work if I try to pass a reference to that class to another class and then use the method from there. Then it forces me to try catch the exception. I probably don't need a factory but it seemed interesting and I'd like to try to use patterns. The reason I created the factory was that I have 6 subclasses of Piece and I wan't to use a method to instantiate them by passing the type of subclass I want as an argument to the method.

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  • API Class with intensive network requests

    - by Marco Acierno
    I'm working an API which works as "intermediary" between a REST API and the developer. In this way, when the programmer do something like this: User user = client.getUser(nickname); it will execute a network request to download from the service the data about the user and then the programmer can use the data by doing things like user.getLocation(); user.getDisplayName(); and so on. Now there are some methods like getFollowers() which execute another network request and i could do it in two ways: Download all the data in the getUser method (and not only the most important) but in this way the request time could be very long since it should execute the request to various urls Download the data when the user calls the method, it looks like the best way and to improve it i could cache the result so the next call to getFollowers returns immediately with the data already download instead of execute again the request. What is the best way? And i should let methods like getUser and getFollowers stop the code execution until the data is ready or i should implement a callback so when the data is ready the callback gets fired? (this looks like Javascript)

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  • menu with: hover, click, class change and ajax

    - by abdullah kahraman
    Hello! I have made a menu that adds class "active" on hover to each li, and removes the class when hovered out, except on li s that has a class "active" already. So far, this is done. However I have another .click() on every li that loads a content to somewhere with ajax. The problem starts here, when I click, I want to add class "active" to clicked element and remove class from all of them. I add the class, but the li that had class "active" before the click doesn't get "active" when hovered, I think the "active" class is not removed from it? Can anyone help? <div id="menu"> <ul> <li><a href="index.php" id="homeLink">home</a></li> <li><a href="#">news</a></li> <li><a id="test" href="#" class="active">blog</a></li> <li><a href="#">gallery</a></li> <li><a href="#">about</a></li> <li><a href="contact.php" id="contactLink">contact</a></li> <li id="ajaxP" style="display:none"><img alt="loading" style="border:none;" src="images/ajax-loader.gif"/></li> </ul> </div> Here is the jquery: $("#menu").find("a").not(".active").each(function(){ $(this).hover(function(){ alert($(this)); $(this).addClass("active"); },function(){ $(this).not(".clicking").removeClass("active"); }); }); $("#homeLink").click(function(){ var myThis=$(this); $("#ajaxP").fadeIn("slow"); $("#normalcontent").hide("slow").load("index.php #normalcontent").slideDown("slow"); $("#primarycontainer").hide("slow").load("index.php #primarycontainer").slideDown("slow"); $("#ajaxP").fadeOut("normal"); $("#menu").find("a").each(function(){ $(this).unbind('mouseover').unbind("mouseout"); $(this).removeClass("active clicking"); }); myThis.addClass("active clicking"); return false; });

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  • How can I run code in a C# class definition each time any instance of the class is deserialized?

    - by Ben
    I am trying to derive a class from ObservableCollection and I need to run just a single line of code each and every time any instance of this class is deserialized. My thought was to do this: [Serializable] public class ObservableCollection2<T> : ObservableCollection<T>, ISerializable { public ObservableCollection2() : base() { } public ObservableCollection2(SerializationInfo info, StreamingContext context) : base(info, context) { // Put additional code here. } void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context) { base.GetObjectData(info, context); } } But I don't have access to those base methods related to serialization. Am I forced to re-write all of the serialization manually?

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  • Using C++, how to call a base class method from a derived class method and apply this to an object passed as an argument?

    - by Chris
    I can't figure out how to call a base class method from a derived class method but concurrently applying this method call at an object passed as argument. What I mean is this: class Animal { virtual void eat(Animal& to_be_eaten) = 0; }; class Carnivores: public Animal { virtual void eat(Animal& to_be_eaten) { /*implementation here*/} }; class Wolf : public Carnivores { virtual void eat(Animal& to_be_eaten) { /*call eat method(of Base class) of Base to_be_eaten here*/ } } I thought of something like this dynamic_cast<Carnivores&>(to_be_eaten).eat(*this) //and got a segmentation fault Is there any way for this to be done? Thank you! New edit:: Updated the code

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  • Encrypt a file base upon a pregenerated "key" C#

    - by Anubis
    Hello everyone. I'm trying to determine the best course of action to implement a simple "licensing" system with a partner of mine. The concept is: Generate an encrypted value based upon several internal hardware components. Have the customer send this value to us which we will implement into our key generator. Once we have that, we add any other restrictions on the license (user, expires, etc.). From there we generate a file which we send to the customer they can add to their installation and voila, happy people about. I have the first part all done. My next part is trying to figure out which encryption methodology I would need to use. I already know Symmetric Encryption is pretty much the only route I can take. Most of the information I have found involves .NET already creating a key from its own internal methods. That's a bit of background, my question is: "Which encryption method could I use which would allow me to encrypt the restrictions based upon the "id" I was given from the customer's computer?" I'm writing this in C# by the way. Any ideas would be greatly appreciated! Take Care!

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  • derived class as default argument g++

    - by Vincent
    Please take a look at this code: template<class T> class A { class base { }; class derived : public A<T>::base { }; public: int f(typename A<T>::base& arg = typename A<T>::derived()) { return 0; } }; int main() { A<int> a; a.f(); return 0; } Compiling generates the following error message in g++: test.cpp: In function 'int main()': test.cpp:25: error: default argument for parameter of type 'A<int>::base&' has type 'A<int>::derived' The basic idea (using derived class as default value for base-reference-type argument) works in visual studio, but not in g++. I have to publish my code to the university server where they compile it with gcc. What can I do? Is there something I am missing?

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  • MCP 1.7.10 Java class navigation

    - by Elias Benevedes
    So, I'm new to the Minecraft modding community and trying to understand where to start. I've attempted to do it before, but dropped it to the complexity of starting and the lack of a site like this to help (Mind that I'm also semi-new to Java, but have worked extensively in Javascript and Python. I understand how Java is different from the two). I have downloaded MCP 9.08 (Decompiles 1.7.10), and decompiled Minecraft. I'm looking to mod client, so I didn't supply it with a server jar. Everything seemed to work fine in decompile (Only error was it couldn't find the server jar). I can find my files in /mcp908/src/minecraft/net/minecraft. However, if I open up one of the classes in, say, block, I see a bunch of variables starting with p_ and ending with _. Is there any way to make these variables more decipherable, to understand what's going on so I can learn by example? Thank you.

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  • Abstract classes in shared library

    - by JTom
    Hi, I have an ordinary abstract class that has couple of pure virtual methods. The class itself is a part of the shared library. The compilation of the shared library itself is OK. But when the library is linked to another program that has another class deriving from the abstract one in the shared library and defining the pure virtual methods, I get the following linker error: I compile like this..: g++ -I../path/to/the/library main.cpp derived.cpp -L../path/to/the/library -lsomename -o shared ...and the linker error is: libsomename.so: undefined reference to `AbstractClass::method()' It's like the abstract class cannot access its pure virtual methods but I do not try to make any instance of the abstract class anywhere in the library. What could be the problem?

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  • Trying to understand the usage of class_eval

    - by eMxyzptlk
    Hello everyone, I'm using the rails-settings gem, and I'm trying to understand how you add functions to ActiveRecord classes (I'm building my own library for card games), and I noticed that this gem uses one of the Meta-programming techniques to add the function to the ActiveRecord::Base class (I'm far from Meta-programming master in ruby, but I'm trying to learn it) module RailsSettings class Railtie < Rails::Railtie initializer 'rails_settings.initialize', :after => :after_initialize do Railtie.extend_active_record end end class Railtie def self.extend_active_record ActiveRecord::Base.class_eval do def self.has_settings class_eval do def settings RailsSettings::ScopedSettings.for_thing(self) end scope :with_settings, :joins => "JOIN settings ON (settings.thing_id = #{self.table_name}.#{self.primary_key} AND settings.thing_type = '#{self.base_class.name}')", :select => "DISTINCT #{self.table_name}.*" scope :with_settings_for, lambda { |var| { :joins => "JOIN settings ON (settings.thing_id = #{self.table_name}.#{self.primary_key} AND settings.thing_type = '#{self.base_class.name}') AND settings.var = '#{var}'" } } scope :without_settings, :joins => "LEFT JOIN settings ON (settings.thing_id = #{self.table_name}.#{self.primary_key} AND settings.thing_type = '#{self.base_class.name}')", :conditions => 'settings.id IS NULL' scope :without_settings_for, lambda { |var| { :joins => "LEFT JOIN settings ON (settings.thing_id = #{self.table_name}.#{self.primary_key} AND settings.thing_type = '#{self.base_class.name}') AND settings.var = '#{var}'", :conditions => 'settings.id IS NULL' } } end end end end end end What I don't understand is why he uses class_eval on ActiveRecord::Base, wasn't it easier if he just open the ActiveRecord::Base class and define the functions? Specially that there's nothing dynamic in the block (What I mean by dynamic is when you do class_eval or instance_eval on a string containing variables) something like this: module ActiveRecord class Base def self.has_settings class_eval do def settings RailsSettings::ScopedSettings.for_thing(self) end scope :with_settings, :joins => "JOIN settings ON (settings.thing_id = #{self.table_name}.#{self.primary_key} AND settings.thing_type = '#{self.base_class.name}')", :select => "DISTINCT #{self.table_name}.*" scope :with_settings_for, lambda { |var| { :joins => "JOIN settings ON (settings.thing_id = #{self.table_name}.#{self.primary_key} AND settings.thing_type = '#{self.base_class.name}') AND settings.var = '#{var}'" } } scope :without_settings, :joins => "LEFT JOIN settings ON (settings.thing_id = #{self.table_name}.#{self.primary_key} AND settings.thing_type = '#{self.base_class.name}')", :conditions => 'settings.id IS NULL' scope :without_settings_for, lambda { |var| { :joins => "LEFT JOIN settings ON (settings.thing_id = #{self.table_name}.#{self.primary_key} AND settings.thing_type = '#{self.base_class.name}') AND settings.var = '#{var}'", :conditions => 'settings.id IS NULL' } } end end end end I understand the second class_eval (before the def settings) is to define functions on the fly on every class that 'has_settings' right ? Same question here, I think he could use "def self.settings" instead of "class_eval.... def settings", no ?

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  • Dynamically creating objects at runtime that inherit from a base class

    - by Homeliss
    I am writing a game editor, and have a lot of different "tool" objects. They all inherit from BTool and have the same constructor. I would like to dynamically populate a toolbox at runtime with buttons that correspond to these tools, and when clicked have them create an instance of that tool and set it as the current tool. Is this possible, and if so will it be better/easier than creating those buttons by hand?

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  • Instantiate proper class based on some input

    - by Adam Backstrom
    I'm attempting to understand how "switch as a code smell" applies when the proper code path is determined by some observable piece of data. My Webapp object sets an internal "host" object based on the hostname of the current request. Each Host subclass corresponds to one possible hostname and application configuration: WwwHost, ApiHost, etc. What is an OOP way for a host subclass to accept responsibility for a specific hostname, and for Webapp to get an instance of the appropriate subclass? Currently, the hostname check and Host instantiation exists within the Webapp object. I could move the test into a static method within the Host subclasses, but I would still need to explicitly list those subclasses in Webapp unless I restructure further. It seems like any solution will require new subclasses to be added to some centralized list.

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  • use jQuery to get 'true size' of image without removing the class

    - by jon3laze
    I am using Jcrop on an image that is resized with css for uniformity. JS <script type="text/javascript"> $(window).load(function() { //invoke Jcrop API and set options var api = $.Jcrop('#image', { onSelect: storeCoords, trueSize: [w, h] }); api.disable(); //disable until ready to use //enable the Jcrop on crop button click $('#crop').click(function() { api.enable(); }); }); function storeCoords(c) { $('#X').val(c.x); $('#Y').val(c.y); $('#W').val(c.w); $('#H').val(c.h); }; </script> HTML <body> <img src="/path/to/image.jpg" id="image" class="img_class" alt="" /> <br /> <span id="crop" class="button">Crop Photo</span> <span id="#X" class="hidden"></span> <span id="#Y" class="hidden"></span> <span id="#W" class="hidden"></span> <span id="#H" class="hidden"></span> </body> CSS body { font-size: 13px; width: 500px; height: 500px; } .image { width: 200px; height: 300px; } .hidden { display: none; } I need to set the h and w variables to the size of the actual image. I tried using the .clone() manipulator to make a copy of the image and then remove the class from the clone to get the sizing but it sets the variables to zeros. var pic = $('#image').clone(); pic.removeClass('image'); var h = pic.height(); var w = pic.width(); It works if I append the image to an element in the page, but these are larger images and I would prefer not to be loading them as hidden images if there is a better way to do this. Also removing the class, setting the variables, and then re-adding the class was producing sporadic results. I was hoping for something along the lines of: $('#image').removeClass('image', function() { h = $(this).height(); w = $(this).width(); }).addClass('image'); But the removeClass function doesn't work like that :P

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  • Loading an NSArray on iPhone from a dynamic data base url in PHP or ASP

    - by Brad
    I have a database online that I would like to be able to load into an NSArray in my app. I can use arrayWithContentsOfURL with a static file, but I really need to go to a url that generates a plist file from the database and loading it into the array. I can use ASP or PHP. I tried setting the response type to "text/xml", but that doesn't help. Any thoughts?

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  • When to use functional programming approach and when not? (in Java)

    - by john smith optional
    let's assume I have a task to create a Set of class names. To remove duplication of .getName() method calls for each class, I used org.apache.commons.collections.CollectionUtils and org.apache.commons.collections.Transformer as follows: Snippet 1: Set<String> myNames = new HashSet<String>(); CollectionUtils.collect( Arrays.<Class<?>>asList(My1.class, My2.class, My3.class, My4.class, My5.class), new Transformer() { public Object transform(Object o) { return ((Class<?>) o).getName(); } }, myNames); An alternative would be this code: Snippet 2: Collections.addAll(myNames, My1.class.getName(), My2.class.getName(), My3.class.getName(), My4.class.getName(), My5.class.getName()); So, when using functional programming approach is overhead and when it's not and why? Isn't my usage of functional programming approach in snippet 1 is an overhead and why?

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  • jQuery arange li order base on #ID

    - by Mircea
    Hi, I have the following code: <ul> <li id="project_25">Proj Something</li> <li id="project_26">Proj Blah</li> <li id="project_27">Proj Else</li> <li id="project_31">Proj More</li> ... </ul> Is there a way to arrange these LIs, reverse their order, based on the LI ID? Something like: <ul> <li id="project_31">Proj More</li> <li id="project_27">Proj Else</li> <li id="project_26">Proj Blah</li> <li id="project_25">Proj Something</li> ... </ul> Thank you.

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  • abstract class in C++

    - by Alexander
    I have a derived derived class from an abstract class. The code is below. I have a FishTank class which is derived from an Aquarium and Aquarium is derived from item. My question is that should I put the definition of virtual int minWidth() const = 0; in aquarium again or is the code below sufficient? class Item{ public: virtual int minWidth() const = 0; }; class Aquarium{ public: virtual int calWidth() = 0; // Pure virtual function. }; class FishTank : public Aquarium{ public: FishTank(int base1, int base2, int height); ~FishTank(); int calWidth(); int minWidth(); };

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  • propertyplaceholderconfigurer class name substitution problem

    - by Alex
    The following example works for "class name substitution using the PropertyPlaceHolderConfigurer": http://forum.springsource.org/showpost.php?p=228136&postcount=2 HOWEVER, when porting this code over (messages.properties, com.spring.ioc.TestClass, and spring-config.xml) to a web application, the class name substitution now fails! 1) I am running on the webapp on Tomcat through the Eclipse plugin. 2) In the web.xml I have the following: <context-param> <param-name>contextConfigLocation</param-name> <param-value>/WEB-INF/spring-config.xml</param-value> </context-param> <listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener> 3) The following is output in the log: 282 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Ignoring bean class loading failure for bean 'test' org.springframework.beans.factory.CannotLoadBeanClassException: Cannot find class [${test.class}] for bean with name 'test' defined in ServletContext resource [/WEB-INF/spring-config.xml]; nested exception is java.lang.ClassNotFoundException: ${test.class} at org.springframework.beans.factory.support.AbstractBeanFactory.resolveBeanClass(AbstractBeanFactory.java:1141) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.predictBeanType(AbstractAutowireCapableBeanFactory.java:524) at org.springframework.beans.factory.support.AbstractBeanFactory.isFactoryBean(AbstractBeanFactory.java:1177) at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanNamesForType(DefaultListableBeanFactory.java:222) at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:505) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:362) at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:255) at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:199) at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:45) at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3795) at org.apache.catalina.core.StandardContext.start(StandardContext.java:4252) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1014) at org.apache.catalina.core.StandardHost.start(StandardHost.java:736) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1014) at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443) at org.apache.catalina.core.StandardService.start(StandardService.java:448) at org.apache.catalina.core.StandardServer.start(StandardServer.java:700) at org.apache.catalina.startup.Catalina.start(Catalina.java:552) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:295) at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:433) Caused by: java.lang.ClassNotFoundException: ${test.class} at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1438) at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1284) at org.springframework.util.ClassUtils.forName(ClassUtils.java:211) at org.springframework.beans.factory.support.AbstractBeanDefinition.resolveBeanClass(AbstractBeanDefinition.java:385) at org.springframework.beans.factory.support.AbstractBeanFactory.resolveBeanClass(AbstractBeanFactory.java:1138) ... 23 more Note: I haven't included it, but the PropertyPlaceHolderConfigurer is successfully locating the messages.properties file, but this seems to happen AFTER the above error is output?! DOES ANYBODY KNOW WHY THIS IS THE CASE AND HOW I CAN OVERCOME THIS PROBLEM?

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  • How to access the backing field of an inherited class using fluent nhibernate

    - by Akk
    How do i set the Access Strategy in the mapping class to point to the inherited _photos field? public class Content { private IList<Photo> _photos; public Content() { _photos = new List<Photo>(); } public virtual IEnumerable<Photo> Photos { get { return _photos; } } public virtual void AddPhoto() {...} } public class Article : Content { public string Body {get; set;} } I am currently using thw following to try and locate the backing field but an exception is thrown as it cannot be found. public class ArticleMap : ClassMap<Article> { HasManyToMany(x => x.Photos) .Access.CamelCaseField(Prefix.Underscore) //_photos //... } i tried moving the backing field _photos directly into the class and the access works. So how can i access the backing field of an inherited class?

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  • Objective-c class initializer executes multiple times

    - by apisip
    Unless I misunderstood it, this LINK from Apple's documentation clearly states that the class initializer, "+ (void)initialize)", only executes once per class. Here is the excerpt: Special Considerations initialize it is invoked only once per class. If you want to perform independent initialization for the class and for categories of the class, you should implement load methods. However, I'm getting a weird behavior on my project and the initializer is being executed twice. So I have to check if _classContext is null. I only got one class that has this method. What are the possible reasons why this is happening? I'm using XCode 4.5.2 and OS X 10.8.2. I got multiple iOS simulators, iPhone 5.1 and 6.0. + (void) initialize { num++; NSLog([NSString stringWithFormat:@"Times: %i", num]); if(_classContext == nil) _classContext = [[myClass alloc] init]; }

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  • Is the a pattern for iterating over lists held by a class (dynamicly typed OO languages)

    - by Roman A. Taycher
    If I have a class that holds one or several lists is it better to allow other classes to fetch those lists(with a getter) or to implement a doXList/eachXList type method for that list that take a function and call that function on each element of the list contained by that object. I wrote a program that did a ton of this and I hated passing around all these lists sometimes with method in class a calling method in class B to return lists contained in class C, B contains a C or multiple C's (note question is about dynamically typed OO languages languages like ruby or smalltalk) ex. (that came up in my program) on a Person class containing scheduling preferences and a scheduler class needing to access them.

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  • Best way to insert items from a Derived class's constructor into a Base class's private std::vector?

    - by Will
    I have these classes: class Base { ... private: std::vector<X> v; }; class Derived { Derived(X*, int n); } where the constructor of Derived is passed an array of item Xs, which I need to insert into my vector v in the Base class. (X is a smart pointer) Currently I see two ways to do this: 1) Create a function in Base: InsertItem(X*) that will insert an item into the vector. 2) Create a vector in Derived that contains the full list, then get it into Base by moving the entire vector. I dont see any advantages to #2, but was wondering if #1 was a good solution, or if there are better ways to do this. Thanks!

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