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  • Why should I abstract my data layer?

    - by Gazillion
    OOP principles were difficult for me to grasp because for some reason I could never apply them to web development. As I developed more and more projects I started understanding how some parts of my code could use certain design patterns to make them easier to read, reuse, and maintain so I started to use it more and more. The one thing I still can't quite comprehend is why I should abstract my data layer. Basically if I need to print a list of items stored in my DB to the browser I do something along the lines of: $sql = 'SELECT * FROM table WHERE type = "type1"';' $result = mysql_query($sql); while($row = mysql_fetch_assoc($result)) { echo '<li>'.$row['name'].'</li>'; } I'm reading all these How-Tos or articles preaching about the greatness of PDO but I don't understand why. I don't seem to be saving any LoCs and I don't see how it would be more reusable because all the functions that I call above just seem to be encapsulated in a class but do the exact same thing. The only advantage I'm seeing to PDO are prepared statements. I'm not saying data abstraction is a bad thing, I'm asking these questions because I'm trying to design my current classes correctly and they need to connect to a DB so I figured I'd do this the right way. Maybe I'm just reading bad articles on the subject :) I would really appreciate any advice, links, or concrete real-life examples on the subject!

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  • jtable update data not visible

    - by Thomas n
    I am running into a problem similar to what I have read here about inserted data and added data not showing up on jtable. I have tried repaint() and revalidate(), but to no avail. Basically, I have two classes say A and B. A calls a function in class B to add a row of data to the table. Here is the code.(By the way I am using Netbeans 7.1.2 to add a table and then add some code to handle the update.) public void callUpdateTable(){ DefaultTableModel myModel = (DefaultTableModel)jTable1.getModel(); DateFormat dateFormate = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss"); Object[] str = new Object[3]; Date date = new Date(); str[0] = dateFormate.format(date); str[1] = "Robot"; str[2] = "hello"; // myModel.addRow(str); myModel.insertRow(1, str); myModel.setValueAt("Hello", 1, 2); System.out.println("count = " + myModel.getValueAt(1, 2)); jTable1.repaint(); } The funny thing is on system print it prints out the value at the cell(1,2) I set the value, but doesn't show up on the table. Thank you for your help.

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  • Why can't we just use a hash of passphrase as the encryption key (and IV) with symmetric encryption algorithms?

    - by TX_
    Inspired by my previous question, now I have a very interesting idea: Do you really ever need to use Rfc2898DeriveBytes or similar classes to "securely derive" the encryption key and initialization vector from the passphrase string, or will just a simple hash of that string work equally well as a key/IV, when encrypting the data with symmetric algorithm (e.g. AES, DES, etc.)? I see tons of AES encryption code snippets, where Rfc2898DeriveBytes class is used to derive the encryption key and initialization vector (IV) from the password string. It is assumed that one should use a random salt and a shitload of iterations to derive secure enough key/IV for the encryption. While deriving bytes from password string using this method is quite useful in some scenarios, I think that's not applicable when encrypting data with symmetric algorithms! Here is why: using salt makes sense when there is a possibility to build precalculated rainbow tables, and when attacker gets his hands on hash he looks up the original password as a result. But... with symmetric data encryption, I think this is not required, as the hash of password string, or the encryption key, is never stored anywhere. So, if we just get the SHA1 hash of password, and use it as the encryption key/IV, isn't that going to be equally secure? What is the purpose of using Rfc2898DeriveBytes class to generate key/IV from password string (which is a very very performance-intensive operation), when we could just use a SHA1 (or any other) hash of that password? Hash would result in random bit distribution in a key (as opposed to using string bytes directly). And attacker would have to brute-force the whole range of key (e.g. if key length is 256bit he would have to try 2^256 combinations) anyway. So either I'm wrong in a dangerous way, or all those samples of AES encryption (including many upvoted answers here at SO), etc. that use Rfc2898DeriveBytes method to generate encryption key and IV are just wrong.

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  • What is an interface in C (COM) is it the same as a interface in C#

    - by numerical25
    Ok, I know what a interface is, but since I got into C and working with COM objects, it seems an interface in COM is a little different from the interface I know of. So what I am trying to do is bridge the gaps here cause since I been learning C, alot of things have been sounding very familiar to me but are not exactly what they seem. The interface I know of are like contracts. They are objects that have only method declarations, with no body. All classes that implement an interface must include the methods of the interface. The interface I hear about in COM seems to be just pointers. They can not retrieve objects directly but only can retrieve objects through the means of a method. Is this what a COM Interface is ?? If so, then why did they give them the same names if they are completely different. Also I just wanted to add that headers in C++ kind of remind me of the C# Interfaces. Not sure if their are any relations. But anyways, I am just trying to clear that up.

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  • ASP.NET Grid with CSS in Rows and Columns

    - by user1089173
    I have the following code List<Department> depts = new List<Department>(); Department.Add(new Department() { DNo = 1, DName = "Accounting", DFloor="6" }); Department.Add(new Department() { DNo = 2, DName = "FInance", DFloor="3" }); I want to bind this data to a GridView, so that it outputs the following. Observe the classes on each th and tr. How can I achieve this in ASP.NET? <thead> <tr> <th class="DNo">DNo</th> <th class="DName">DName</th> <th class= "DFloor">DFloor</th> </tr> </thead> <tr> <td class="DNo">1</td> <td class="DName">Accounting</td> <td class="DFloor">6</td> </tr> <tr> <td class="DNo">2</td> <td class="DName">FInance</td> <td class="DFloor">3</td> </tr>

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  • Serializing a class containing a custom class

    - by Netfangled
    I want to serialize an object as xml that contains other custom classes. From what I understand (I've been reading MSDN and SO mostly), the XmlSerializer doesn't take this into account. This is the line that's confusing me: XML serialization serializes only the public fields and property values of an object into an XML stream. XML serialization does not include type information. For example, if you have a Book object that exists in the Library namespace, there is no guarantee that it will be deserialized into an object of the same type. Taken from MSDN, here For example, I want to serialize an object of type Order, but it contains a list of Products, and each one contains an object of type Category: class Order { List<Product> products; } class Product { Category type; } class Category { string name; string description; } And I want my Order object to be serialized like so: <Order> <Product> <Category Name=""> <Description></Description> </Category> </Product> <Product> <Category Name=""> <Description></Description> </Category> </Product> <Order> Does the XmlSerializer already do this? If not, is there another class that does or do I have to define the serialization process myself?

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  • Activator.CreateInstance uses a huge amount of memory

    - by Marco
    I have been playing a bit with Silverlight and try to port my Silverlight 3.0 application to Silverlight 4.0. My application loads different XAP files and upon a user request create an instance of a Xaml user control and adds it to the main container, in a sort of MEF approach in order I can have an extensible and pluggable application. The application is pretty huge and to keep acceptable the performances and the initial loading I have built up some helper classes to load in the background all pages and user controls that might be used later on. On Silverlight 3.0 everything was running smoothly without any problem so far. Switching to SL 4.0 I have noticed that when the process approaches to create the instances of the user controls using Activator.CreateInstance, the layout freezes unexpectedly for a minute and sometimes for more. Looking at the task manager the memory usage of IE jumps from 50MB to 400MB and sometimes to 1.5 GB. If the process won't take that much the layout is rendered properly and the memory falls back to 50 MB. Otherwise everything crashes due to out of memory exeption. Does anybody encountered the same problem? Or has anybody a solution about this tricky issue?

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  • Passing an arbritrary JavaScript object in Xul

    - by Tom Brito
    I'm following this example to pass an object to a window, but when it as an argument it's with "undefined" value. This is my first window (obs. dump is the way to print to console when debug options are turned on): <?xml version="1.0"?> <?xml-stylesheet href="chrome://global/skin/" type="text/css"?> <!DOCTYPE window SYSTEM "chrome://XulWindowArgTest/locale/XulWindowArgTest.dtd"> <window id="windowID" width="400" height="300" xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"> <script> <![CDATA[ function onClickMe(event) { dump("begin\n"); try { var args = { param1: true, param2: 42 }; args.wrappedJSObject = args; var watcher = Components.classes["@mozilla.org/embedcomp/window-watcher;1"].getService(Components.interfaces.nsIWindowWatcher); watcher.openWindow(null, "chrome://XulWindowArgTest/content/about.xul", "windowName", "chrome", args); } catch (e) { dump("error: " + e + "\n"); } dump("end\n"); } ]]> </script> <button label="Click me !" oncommand="onClickMe();" /> </window> and my second window: <?xml version="1.0"?> <?xml-stylesheet href="chrome://global/skin/" type="text/css"?> <!DOCTYPE window SYSTEM "chrome://XulWindowArgTest/locale/XulWindowArgTest.dtd"> <window xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul" onload="onload()"> <script> <![CDATA[ function onload() { dump('arg = ' + window.arguments[0].wrappedJSObject + "\n"); } ]]> </script> <label value="test" /> </window> when the second window loads, it calls the onload and prints: arg = undefined Any idea how to fix it?

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  • JDO architecture: One to many relationship and cascading deleting

    - by user361897
    I’m new to object oriented database designs and I’m trying to understand how I should be structuring my classes in JDO for google app engine, particularly one to many relationships. Let’s say I’m building a structure for a department store where there are many departments, and each department has many products. So I’d want to have a class called Department, with a variable that is a list of a Product class. @PersistenceCapable public class Department { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) private String deptID; @Persistent private String departmentName; @Persistent private List<Product>; } @PersistenceCapable public class Product { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) private String productID; @Persistent private String productName; } But one Product can be in more than one Department (like a battery could be in electronics and household supplies). So the next question is, how do I not duplicate data in the OOD world and have only one copy of product data in numerous departments? And the next question is, let’s say I delete out a particular product, how do each of the departments know it was deleted?

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  • Which options do I have for Java process communication?

    - by Dmitriy Matveev
    We have a place in a code of such form: void processParam(Object param) { wrapperForComplexNativeObject result = jniCallWhichMayCrash(param); processResult(result); } processParam - method which is called with many different arguments. jniCallWhichMayCrash - a native method which is intended to do some complex processing of it's parameter and to create some complex object. It can crash in some cases. wrapperForComplexNativeObject - wrapper type generated by SWIG processResult - a method written in pure Java which processes it's parameter by creation of several kinds (by the kinds I'm not meaning classes, maybe some like hierarchies) of objects: 1 - Some non-unique objects which are referencing each other (from the same hierarchy), these objects can have duplicates created from the invocations of processParam() method with different parameter values. Since it's costly to keep all the duplicates it's necessary to cache them. 2 - Some unique objects which are referencing each other (from the same hierarchy) and some of the objects of 1st kind. After processParam is executed for each of the arguments from some set the data created in processResult will be processed together. The problem is in fact that jniCallWhichMayCrash method may crash the entire JVM and this will be very bad. The reason of crash may be such that it can happen for one argument value and not for the other. We've decided that it's better to ignore crashes inside of JVM and just skip some chunks of data when such crashes occur. In order to do this we should run processParam function inside of separate process and pass the result somehow (HOW? HOW?! This is a question) to the main process and in case of any crashes we will only lose some part of data (It's ok) without lose of everything else. So for now the main problem is implementation of transport between different processes. Which options do I have? I can think about serialization and transmitting of binary data by the streams, but serialization may be not very fast due to object complexity. Maybe I have some other options of implementing this?

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  • CSS - Why is this invisible margin being applied to my <a> tag css-button?

    - by Kenny Bones
    I was having trouble with two types of buttons. It was a form button and a css button basically. And I was advised that the css button whould use display:inline-block; This made the whole a href tag actually look like a button. But this invisible margin seems to be screwing up something. I tried separating them into separate css classes, but oddly, applying a real margin to the css button gives an additional margin as well. What's causing this? You can easily see it here (low graphics): www.matkalenderen.no Basically, code looks like this: <input type="submit" value="Logg inn" class="button_blue" alt="ready to login"> <a class="button_css_red" href="access.php">Glemt passord</a> CSS .button_red, .button_blue, .button_css_red, .button_css_blue { background-image:url("../img/sprite_buttons.png"); background-repeat:no-repeat; border: none; color:#FFFFFF; display:inline-block; display:inline-block; font-size:12px; height:27px; width:98px; } .button_css_red, .button_css_blue { margin-top:20px; }

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  • C++ Dynamic object construction

    - by Rajesh Subramanian
    I have a base class, class Msg { ParseMsg() { ParseMsgData(); ParseTrailer(); } virtual void ParseMsgData() = 0; ParseTrailer(); }; and derived classes, class InitiateMsg { void ParseMsgData() { ... } }; class ReadOperationMsg { void ParseMsgData() { ... } }; class WriteOperationMsg { void ParseMsgData() { ... } }; and the scenario is below, void UsageFunction(string data) { Msg* msg = ParseHeader(data); ParseMsg } Msg* ParseHeader(string data) { Msg *msg = NULL; .... switch() { case 1: msg = new InitiateMsg(); break; case 2: msg = new ReadOperationMsg{(); break; case 3: msg = new WriteOperationMsg{(); break; .... } return msg; } based on the data ParseHeader method will decide which object has to be created, So I have implemented ParseHeader function outside the class where I am using. How can I make the ParseHeader function inside the Msg class and then use it? In C# the same is achieved by defining ParseHeader method as static with in class and use it from outside,

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  • Debugging scripts loaded with GroovyShell (in eclipse)

    - by MSh
    I am working with eclipse and groovy plug in. I am building a test harness to debug and test groovy scripts. The scripts are really simple but long, most of them just if/else/return. I figured out that I can call them using GroovyShell and Bindings to pass in the values. The problem is that, while I can call the script and get the results just fine, I CAN NOT step in there with the debugger. Breakpoints in those scripts are not active. Is there a way to debug the scripts? Maybe I should use something other than GroovyShell? I really don't want to modify the scripts by wrapping them into functions, and then calling those functions from my test classes. That's how I am using Binding and GroovyShell: def binding = new Binding(); binding.lineList = [list1]; binding.count = 5; def shell = new GroovyShell(binding); def result = shell.evaluate(new File("src/Rules/checkLimit.groovy"));

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  • Best way to design a class in python

    - by Fraz
    So, this is more like a philosophical question for someone who is trying to understand classes. Most of time, how i use class is actually a very bad way to use it. I think of a lot of functions and after a time just indent the code and makes it a class and replacing few stuff with self.variable if a variable is repeated a lot. (I know its bad practise) But anyways... What i am asking is: class FooBar: def __init__(self,foo,bar): self._foo = foo self._bar = bar self.ans = self.__execute() def __execute(self): return something(self._foo, self._bar) Now there are many ways to do this: class FooBar: def __init__(self,foo): self._foo = foo def execute(self,bar): return something(self._foo, bar) Can you suggest which one is bad and which one is worse? or any other way to do this. This is just a toy example (offcourse). I mean, there is no need to have a class here if there is one function.. but lets say in __execute something() calls a whole set of other methods.. ?? Thanks

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  • In Java, is there a performance gain in using interfaces for complex models?

    - by Gnoupi
    The title is hardly understandable, but I'm not sure how to summarize that another way. Any edit to clarify is welcome. I have been told, and recommended to use interfaces to improve performances, even in a case which doesn't especially call for the regular "interface" role. In this case, the objects are big models (in a MVC meaning), with many methods and fields. The "good use" that has been recommended to me is to create an interface, with its unique implementation. There won't be any other class implementing this interface, for sure. I have been told that this is better to do so, because it "exposes less" (or something close) to the other classes which will use methods from this class, as these objects are referring to the object from its interface (all public methods from the implementation being reproduced in the interface). This seems quite strange to me, as it seems like a C++ use to me (with header files). There I see the point, but in Java? Is there really a point in making an interface for such unique implementation? I would really appreciate some clarifications on the topic, so I could justify not following such kind of behavior, and the hassle it creates from duplicating all declarations. Edit: Plenty of valid points in most answers, I'm wondering if I won't switch this question for a community wiki, so we can regroup these points in more structured answers.

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  • GUI for server-client program

    - by sksingh73
    I am making a server-client application in c++. In this i am also using shared memory & file read-write operations. my program is completely ready & i now wants to make a gui for it. someone suggested me to go for QT4, but when i tried it, i found i have to re-write 80% of the code because QT has got its own classes & variable. i don't want to do it. i want suggestions from you on this regard. my requirements for gui are very simple i.e there will be a main form, which will have two text boxes in which all messages being sent & received by client & server should be shown. there should be another lineedit box, through which i can send the messages to the other end server. I don't know how to make this gui. someone suggested tcl/tk, other suggested me use php/swig. i am not sure how to go about this. my only requirement is that i want to make this simple gui with minimum of changes in my code. THANX

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  • In Ruby or Python can the very idea of Class be rewritten?

    - by John Berryman
    Howdy All... first time at stack overflow. I'm looking into using some of the metaprogramming features provided by Ruby or Python, but first I need to know the extent to which they will allow me to extend the language. The main thing I need to be able to do is to rewrite the concept of Class. This doesn't mean that I want to rewrite a specific class during run time, but rather I want to make my own conceptualization of what a Class is. To be a smidge more specific here, I want to make something that is like what people normally call a Class, but I want to follow an "open world" assumption. In the "closed world" of normal Classes, if I declare Poodle to be a subclass of Dog to be a subclass of Animal, then I know that Poodle is not going to also be a type of FurCoat. However, in an open world Class, then the Poodle object I've defined may or may not be and object of type FurCoat and we won't know for sure until I explain that I can wear the poodle. (Poor poodle.) This all has to do with a study I'm doing concerning OWL ontologies. Just so you know, I've tried to find information online, but due to the overloading of terms here I haven't found anything helpful. Super thanks, John

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  • Add file in ANT build (Tomcat server)

    - by Shaded
    Hey everyone, I have an ANT build that I need to setup so on deployment of the .war a certain file will be placed in a specific location. Currently my ant builds the war as follows... <target name="war" depends="jar"> <war destfile="${deploy}/file.war" webxml="${web-inf}/web.xml"> <fileset dir="${WebRoot}"> <include name="**/*.vm" /> <include name="**/*.js" /> <include name="**/*.jsp" /> <include name="**/*.html" /> <include name="**/*.css" /> <include name="**/*.gif" /> <include name="**/*.jpg" /> <include name="**/*.png" /> <include name="**/*.tld" /> <include name="**/applicationContext*.xml" /> <include name="**/jpivot/**" /> <include name="**/wcf/**" /> <include name="**/platform/**" /> <include name="**/Reports/**" /> </fileset> <lib dir="${web-inf.lib}" /> </war> </target> The file I need is called Scriptlet.class and it needs to be in WebRoot/WEB-INF/classes/ I've tried several things to get this to work and have yet to find one that works... if anyone can point me in the right direction I'd appreciate it!

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  • Is there a proper and wrong way to format CSS?

    - by DavidR
    When I first started writing CSS, I was writing it in an expanded form div.class { margin: 10px 5px 3px; border: 1px solid #333; font-weight: bold; } .class .subclass { text-align:right; } but now I find myself writing css like this: (Example from code I'm actually writing now) .object1 {} .scrollButton{width:44px;height:135px;} .scrollButton img {padding:51px 0 0 23px;} .object2 {width:165px;height:94px;margin:15px 0 0 23px;padding:15px 0 0 10px;background:#fff;} .featuredObject .symbol{line-height:30px; padding-top:6px;} .featuredObject .value {width:90px;} .featuredObject .valueChange {padding:5px 0 0 0;} .featuredObject img {position:absolute;margin:32px 0 0 107px;} and I'm beginning to worry because a lot of the time I see the first form done in examples online, while I find the second form a lot easier for me to work with. It has a lower vertical height, so I can see all the classes at a glance with less scrolling, the tabulation of the hierarchy seems more apparent, and it looks more like code I'd write with javascript or html. Is this a valid way of doing code, or to keep with standards when putting it online should I use the vertical form instead?

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  • what patern is layerd architechture in asp.net ?

    - by haansi
    Hi, I am a asp.net developer and don't know much about patterns and architecture. I will very thankful if you can please guide me here. In my web applications I use 4 layers. Web site project (having web forms + code behind cs files, user controls + code behind cs files, master pages + code behind cs files) CustomTypesLayer a class library (having custom types, enumerations, DTOs, constructers, get, set and validations) BusinessLogicLayer a class library (having all business logic, rules and all calls to DAL functions) DataAccessLayer a class library( having just classes communicating to database.) -My user interface just calls BusinessLogicLayer. BusinessLogicLayer do proecessign in it self and for data it calls DataAccessLayer funtions. -Web forms do not calls directly DAL. -CustomTypesLayer is shared by all layers. Please guide me is this approach a pattern ? I though it may be MVC or MVP but pages have there code behind files as well which are confusing me. If it is no patren is it near to some patren ? pleaes guide thanks

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  • Hibernate many-to-one - bad usage?

    - by DaveA
    Just trying out Hibernate (with Annotations) and I'm having problems with my mappings. I have two entity classes, AudioCD and Artist. @Entity public class AudioCD implements CatalogItem { @Id @GeneratedValue(strategy = GenerationType.AUTO) private int id; private String title; @ManyToOne(cascade = { CascadeType.ALL }, optional = false) private Artist artist; .... } @Entity @Table(uniqueConstraints = { @UniqueConstraint(columnNames = { "name" }) }) public class Artist { @Id @GeneratedValue(strategy = GenerationType.AUTO) private int id; @Column(nullable = false) private String name; ..... } I get AudioCD objects from an external source. When I try to persist the AudioCD the Artist gets persisted as well, just like I want to happen. If I try persisting another different CD, but Artist already exists I get errors due to constraint violations. I want Hibernate to recognise that the Artist already exists and shouldn't be inserted again. Can this be done via annotations? Or do I have to manage the persistence of the AudioCD and Artist seperately?

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  • Implementation help... Subclass NSManagedObject?

    - by Canada Dev
    I'm working on an app where I have some products that I download in a list. The downloaded products are displayed in a table and each will is showing a detail view with more information. These same products can be saved as a favorite, and for this I am using Core Data. I'd like to be able to re-use a bunch of views for displaying the products, which means the stores object and the downloaded object would have to be the same kind. Now, how would I go about best implementing the objects? Can I make a class such as this: FavoriteProduct : NSManageObject // implementation and then subclass Product : FavoriteProduct // implementation ? The CD class just doesn't give me everything. What would be the best way to merge these two object classes so I have as little work ahead of me in terms of implementing the different views for each object? Basically, I just want to be able to call the same methods, etc. on the Product objects as I would on the ones that are FavoriteProduct objects, and re-use views for both kinds. There's only a bit of difference between the two (one is of course stored as a favorite and has some extra values such as notes, tags, while the Product one doesn't). Thanks in advance

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  • C++ private inheritance and static members/types

    - by WearyMonkey
    I am trying to stop a class from being able to convert its 'this' pointer into a pointer of one of its interfaces. I do this by using private inheritance via a middle proxy class. The problem is that I find private inheritance makes all public static members and types of the base class inaccessible to all classes under the inheriting class in the hierarchy. class Base { public: enum Enum { value }; }; class Middle : private Base { }; class Child : public Middle { public: void Method() { Base::Enum e = Base::value; // doesn't compile BAD! Base* base = this; // doesn't compile GOOD! } }; I've tried this in both VS2008 (the required version) and VS2010, neither work. Can anyone think of a workaround? Or a different approach to stopping the conversion? Also I am curios of the behavior, is it just a side effect of the compiler implementation, or is it by design? If by design, then why? I always thought of private inheritance to mean that nobody knows Middle inherits from Base. However, the exhibited behavior implies private inheritance means a lot more than that, in-fact Child has less access to Base than any namespace not in the class hierarchy!

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  • java: assigning object reference IDs for custom serialization

    - by Jason S
    For various reasons I have a custom serialization where I am dumping some fairly simple objects to a data file. There are maybe 5-10 classes, and the object graphs that result are acyclic and pretty simple (each serialized object has 1 or 2 references to another that are serialized). For example: class Foo { final private long id; public Foo(long id, /* other stuff */) { ... } } class Bar { final private long id; final private Foo foo; public Bar(long id, Foo foo, /* other stuff */) { ... } } class Baz { final private long id; final private List<Bar> barList; public Baz(long id, List<Bar> barList, /* other stuff */) { ... } } The id field is just for the serialization, so that when I am serializing to a file, I can write objects by keeping a record of which IDs have been serialized so far, then for each object checking whether its child objects have been serialized and writing the ones that haven't, finally writing the object itself by writing its data fields and the IDs corresponding to its child objects. What's puzzling me is how to assign id's. I thought about it, and it seems like there are three cases for assigning an ID: dynamically-created objects -- id is assigned from a counter that increments reading objects from disk -- id is assigned from the number stored in the disk file singleton objects -- object is created prior to any dynamically-created object, to represent a singleton object that is always present. How can I handle these properly? I feel like I'm reinventing the wheel and there must be a well-established technique for handling all the cases.

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  • How do I access abstract private data from derived class without friend or 'getter' functions in C++?

    - by John
    So, I am caught up in a dilemma right now. How am I suppose to access a pure abstract base class private member variable from a derived class? I have heard from a friend that it is possible to access it through the base constructor, but he didn't explain. How is it possible? There are some inherited classes from base class. Is there any way to gain access to the private variables ? class Base_button { private: bool is_vis; Rect rButton; public: // Constructors Base_button(); Base_button( const Point &corner, double height, double width ); // Destructor virtual ~ Base_button(); // Accessors virtual void draw() const = 0; bool clicked( const Point &click ) const; bool is_visible() const; // Mutators virtual void show(); virtual void hide(); void move( const Point &loc ); }; class Button : public Base_button { private: Message mButton; public: // Constructors Button(); Button( const Point &corner, const string &label ); // Acessors virtual void draw() const; // Mutators virtual void show(); virtual void hide(); }; I want to be able access Rect and bool in the base class from the subclass

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