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  • How to make some functions of a class as private for third level of inheritance.

    - by Shantanu Gupta
    I have created a class say A which has some functions defined as protected. Now Class B inherits A and class C inherits B. Class A has private default constructor and protected parameterized constructor. I want Class B to be able to access all the protected functions defined in Class A but class C can have access on some of the functions only not all the functions and class C is inheriting class B. How can I restrict access to some of the functions of Class A from Class C ? Class A { private A(){} protected A(int ){} protected calc(){} protected allow(){} } Class B : A {} // calc() and allow() should be accessible here CLass C:B { // calc() should not be accessible here but allow() should be accessible here. }

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  • What does ER_WARN_FIELD_RESOLVED mean?

    - by VolkerK
    When SHOW WARNINGS after a EXPLAIN EXTENDED shows a Note 1276 Field or reference 'test.foo.bar' of SELECT #2 was resolved in SELECT #1 what exactly does that mean and what impact does it have? In my case it prevents mysql from using what seems to be a perfectly good index. But it's not about fixing that specific query (as it is an irrelevant test). I found http://dev.mysql.com/doc/refman/5.0/en/error-messages-server.html butError: 1276 SQLSTATE: HY000 (ER_WARN_FIELD_RESOLVED) Message: Field or reference '%s%s%s%s%s' of SELECT #%d was resolved in SELECT #%d isn't much of an explaination.

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  • Database: Storing Dates as Numeric Values

    - by Chin
    I'm considering storing some date values as ints. i.e 201003150900 Excepting the fact that I lose any timezone information, is there anything else I should be concerned about with his solution? Any queries using this column would be simple 'where after or before' type lookups. i.e Where datefield is less than 201103000000 (before March next year). currently the app is using MSSQL2005. Any pointers to pitfalls appreciated.

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  • Need some clarification with Patterns (DAO x Gateway)

    - by Marcos Placona
    Me and my colleagues got into this discussion early this morning, and our opinions started to clash a bit, so I decided to get some impartial advice here. One of my colleagues reckons that the DAO should return an object (populated bean). I think it's completely fine when you're returning a recordset with only one line, but think it's overkill if you have to return 10 lines, and create 10 separate objects. I on the other see that the difference between DAO and Gateway pattern is that the gateway pattern will allow you to return a recordset to your business class, which will therefore deal with the recordset data and do whatever it needs to do. My questions here are: Which assumptions are correct? What should the return type be for a DAO (i.e. getContact() - for one record) Should getContacts() (for multiple records) even be on the DAO, if so, what's it's returntype? We seem to be having some sort of confusion about DAO and Gateway Patterns. Should they be used together? Thanks in advance

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  • Is there an ORM that supports composition w/o Joins

    - by Ken Downs
    EDIT: Changed title from "inheritance" to "composition". Left body of question unchanged. I'm curious if there is an ORM tool that supports inheritance w/o creating separate tables that have to be joined. Simple example. Assume a table of customers, with a Bill-to address, and a table of vendors, with a remit-to address. Keep it simple and assume one address each, not a child table of addresses for each. These addresses will have a handful of values in common: address 1, address 2, city, state/province, postal code. So let's say I'd have a class "addressBlock" and I want the customers and vendors to inherit from this class, and possibly from other classes. But I do not want separate tables that have to be joined, I want the columns in the customer and vendor tables respectively. Is there an ORM that supports this? The closest question I have found on StackOverflow that might be the same question is linked below, but I can't quite figure if the OP is asking what I am asking. He seems to be asking about foregoing inheritance precisely because there will be multiple tables. I'm looking for the case where you can use inheritance w/o generating the multiple tables. Model inheritance approach with Django's ORM

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  • When do you trust the data / variables

    - by Wizzard
    We all know that all user data, GET/POST/Cookie etc etc needs to be validated for security. But when do you stop, once it's converted into a local variable? eg if (isValidxxx($_GET['foo']) == false) { throw InvalidArgumentException('Please enter a valid foo!'); } $foo = $_GET['foo']; fooProcessor($foo); function fooProcessor($foo) { if (isValidxxx($foo) == false) { throw Invalid...... } //other stuff } To me thats over the top. But what if you load the value from the database... I hope I make sense :)

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  • Managing inverse relationships without CoreData

    - by Nathaniel Martin
    This is a question for Objective-J/Cappuccino, but I added the cocoa tag since the frameworks are so similar. One of the downsides of Cappuccino is that CoreData hasn't been ported over yet, so you have to make all your model objects manually. In CoreData, your inverse relationships get managed automatically for you... if you add an object to a to-many relationship in another object, you can traverse the graph in both directions. Without CoreData, is there any clean way to setup those inverse relationships automatically? For a more concrete example, let's take the typical Department and Employees example. To use rails terminology, a Department object has-many Employees, and an Employee belongs-to a Department. So our Department model has an NSMutableSet (or CPMutableSet ) "employees" that contains a set of Employees, and our Employee model has a variable "department" that points back to the Department model that owns it. Is there an easy way to make it so that, when I add a new Employee model into the set, the inverse relationship (employee.department) automatically gets set? Or the reverse: If I set the department model of an employee, then it automatically gets added to that department's employee set? Right know I'm making an object, "ValidatedModel" that all my models subclass, which adds a few methods that setup the inverse relationships, using KVO. But I'm afraid that I'm doing a lot of pointless work, and that there's already an easier way to do this. Can someone put my concerns to rest?

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  • Is it possible to create a domain model for legacy code without refactoring?

    - by plaureano
    I currently have a client that wants me to 'abstract' out a domain model from the existing code but they specifically said that I shouldn't refactor the existing code itself. My question is 1) whether or not this is advisable and 2) what techniques would you apply in this scenario if you can't refactor the code yet they expect you to come up with a model for it? (EDIT: I can't quite put my finger on it, but somehow, not being able to refactor in this case just feels wrong. Has anyone else run into this type of scenario?)

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  • Should I use custom exceptions to control the flow of application?

    - by bonefisher
    Is it a good practise to use custom business exceptions (e.g. BusinessRuleViolationException) to control the flow of user-errors/user-incorrect-inputs??? The classic approach: I have a web service, where I have 2 methods, one is the 'checker' (UsernameAlreadyExists()) and the other one is 'creator' (CreateUsername())... So if I want to create a username, I have to do 2 roundtrips to webservice, 1.check, 2.if check is OK, create. What about using UsernameAlreadyExistsException? So I call only the 2. web service method (CrateUsername()), which contains the check and if not successfull, it throws the UsernameAlreadyExistsException. So the end goal is to have only one round trip to web service and the checking can be contained also in other web service methods (so I avoid calling the UsernameAlreadyExists() all the times..). Furthermore I can use this kind of business error handling with other web service calls completely avoiding the checking prior the call.

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  • Cleanly handling events

    - by nkr1pt
    I have code similar to this in all my observer classes that handle events fired by an event bus class. As you can see there are a lot of instanceof checks to choose the path of action needed to appropriately handle events, and I was wondering if this could be done more cleanly, eliminating the instanceof tests? @Override public void handleEvent(Event event) { if (event instanceof DownloadStartedEvent) { DownloadStartedEvent dsEvent = (DownloadStartedEvent)event; dsEvent.getDownloadCandidateItem().setState(new BusyDownloadingState()); } else if (event instanceof DownloadCompletedEvent) { DownloadCompletedEvent dcEvent = (DownloadCompletedEvent)event; dcEvent.getDownloadCandidateItem().setState(new FinishedDownloadingState()); DownloadCandidate downloadCandidate = dcEvent.getDownloadCandidateItem(). getDownloadCandidate(); if (downloadCandidate.isComplete()) { // start extracting } } else if (event instanceof DownloadFailedEvent) { DownloadFailedEvent dfEvent = (DownloadFailedEvent)event; dfEvent.getDownloadCandidateItem().setState(new FailedDownloadingState()); } }

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  • PHP Object References in Frameworks

    - by bigstylee
    Before I dive into the disscusion part a quick question; Is there a method to determine if a variable is a reference to another variable/object? For example $foo = 'Hello World'; $bar = &$foo; echo (is_reference($bar) ? 'Is reference' : 'Is orginal'; I have been using PHP5 for a few years now (personal use only) and I would say I am moderately reversed on the topic of Object Orientated implementation. However the concept of Model View Controller Framework is fairly new to me. I have looked a number of tutorials and looked at some of the open source frameworks (mainly CodeIgnitor) to get a better understanding how everything fits together. I am starting to appreciate the real benefits of using this type of structure. I am used to implementing object referencing in the following technique. class Foo{ public $var = 'Hello World!'; } class Bar{ public function __construct(){ global $Foo; echo $Foo->var; } } $Foo = new Foo; $Bar = new Bar; I was surprised to see that CodeIgnitor and Yii pass referencs of objects and can be accessed via the following method: $this->load->view('argument') The immediate advantage I can see is a lot less code and more user friendly. But I do wonder if it is more efficient as these frameworks are presumably optimised? Or simply to make the code more user friendly? This was an interesting article Do not use PHP references.

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  • Is the set of data always normalized in one form or the other in Databases

    - by manugupt1
    Suppose I have a set of data, given the data and the relation schemas can I assume that the set of data is normalized in one form or the other. In my opinion raw data given, has to be normalized into some form. However a discussion with a friend has led to ask me this question here. To expound more on the question, I would say given a set of functional dependencies for a relation or table, is it guaranteed that the table would atleast be in 1NF if not others

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  • I want define tables from a part of my ER Diagram.

    - by M R Jafari
    I have a ER-Diagram (Show in http://www.4freeimagehost.com/show.php?i=f82997ca4d5d.png). In the diagram you see 2 entities and a 1:N relataion together. Project has 2 columns as ProjectID, ProjectName. Employee has 3 colums as EmployeeID, EmployeeName and ProjectID. A project has ONLY 1 project-manager and project-manager is a employee. What columns add them?

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  • Building a professional company website

    - by Sphynx
    Hi fellows, I want to create a professional website for my company. I'm not a designer. I know some html/css, but I don't have much experience making up advanced pages and layouts. I'd expect public area, with various articles, and a "customer zone", accessible via username and password, where clients will be able to track their orders and download files. It needs to look very modern. I don't want to use website templates, because they're too simple. I know some Wordpress, but that's mostly for blogs, and anyways you need to find a right theme besides the CMS itself... Is there any alternative solution, some kind of framework for building such portals? Preferably a system that doesn't require designer skills. Thanks!

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  • strategy for observer pattern?

    - by fayer
    I want to use observer pattern for a logging system. We have got logObservers and logObservables. The class that will have to log something will implement iLogObservable and include these methods: private $logObservers = array(); public function addLogObserver($logObserver) { $this->logObservers[] = $logObserver; } public function removeLogObserver($logObserver) { $this->logObservers[] = $logObserver; } public function write($type, $message) { foreach($this->logObservers as $logObserver) { $logObserver->log($level, $message); ; } } Then I noticed, that a lot of classes that will use logging will have these methods and I have to copy paste. So isn't it better to have these methods in a class I call LogObservable or just Log and then use strategy (instantiate this class inside all classes that will have to log). When I change the methods in Log, all logObservables will be affected. However, I have not seen anyone use observer pattern with strategy pattern yet, but it seems to be very efficient and remove the duplications. What do you think?

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  • How can I handle dynamic calculated attributes in a model in Django?

    - by bullfish
    In Django I calculate the breadcrumb (a list of fathers) for an geographical object. Since it is not going to change very often, I am thinking of pre calculating it once the object is saved or initialized. 1.) What would be better? Which solution would have a better performance? To calculate it at _init_ or to calculate it when the object is saved (the object takes about 500-2000 characters in the DB)? 2.) I tried to overwrite the _init_ or save() methods but I don't know how to use attributes of the just saved object. Accessing *args, **kwargs did not work. How can I access them? Do I have to save, access the father and then save again? 3.) If I decide to save the breadcrumb. Whats the best way to do it? I used http://www.djangosnippets.org/snippets/1694/ and have crumb = PickledObjectField(). Thats the method to calculate the attribute crumb() def _breadcrumb(self): breadcrumb = [ ] x = self while True: x = x.father try: if hasattr(x, 'country'): breadcrumb.append(x.country) elif hasattr(x, 'region'): breadcrumb.append(x.region) elif hasattr(x, 'city'): breadcrumb.append(x.city) else: break except: break breadcrumb.reverse() return breadcrumb Thats my save-Method: def save(self,*args, **kwargs): # how can I access the father ob the object? father = self.father # does obviously not work father = kwargs['father'] # does not work either # the breadcrumb gets calculated here self.crumb = self._breadcrumb(father) super(GeoObject, self).save(*args,**kwargs) Please help me out. I am working on this for days now. Thank you.

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  • How to store data in mysql, to get the fastest performance?

    - by Oden
    Hey, I'm thinking about it, witch of the following two query types would give me the fastest performance for a user messaging module inside my site: The first one i thought about is a multi table setup, witch has a connection table, and a main table. The connection table holds the connection between accounts, and the messaging table. In this case a query would look like following, to get some data of the author, and the messages he has sent: SELECT m.*, a.username FROM messages AS m LEFT JOIN connection_table ON (message_id = m.id) LEFT JOIN accounts AS a ON (account_id = a.id) WHERE m.id = '32341' Inserting into it is a little bit more "complicated". My other idea, and in my thought the better solution of this problem is that i store the data i would use in a connection table in the same table where is store the data of the mail. Sounds like i would get lots of duplicated entries, but no, because i have a field witch has text type and holds user ids like this: *24*32*249* If I want to query them, i use the mysql LIKE method. Deleting is an other problem, but for this i have one more field where i store who has deleted the post. Sad about that i don't know how to join this. So what would you recommend? Are there other ways?

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  • [Delphi] How would you refactor this code?

    - by Al C
    This hypothetical example illustrates several problems I can't seem to get past, even though I keep trying!! ... Suppose the original code is a long event handler, coded in the UI, triggered when a user clicks a cell in a grid. Expressed as pseudocode it's: if Condition1=true then begin //loop through every cell in row, //if aCell/headerCellValue>1 then //color aCell red end else if Condition2=true then begin //do some other calculation adding cell and headerCell values, and //if some other product>2 then //color the whole row green end else show an error message I look at this and say "Ah, refactor to the strategy pattern! The code will be easier to understand, easier to debug, and easier to later extend!" I get that. And I can easily break the code into multiple procedures. The problem is ultimately scope related. Assume the pseudocode makes extensive use of grid properties, values displayed in cells, maybe even built-in grid methods. How do you move all that to another unit, without referencing the grid component in the UI--which would break all the "rules" about loose coupling that make OOP valuable? ... I'm really looking forward to responses. Thanks, as always -- Al C.

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  • Low cost way to host a large table yet keep the performance scalable?

    - by Leo Liang
    I have a growing table storing time series data, 500M entries now, and 200K new records every day. The total size is around 15GB for now. My clients are querying the table via a PHP script mostly, and the size of the result set is around 10K records (not very large). select * from T where timestamp > X and timestamp < Y and additionFilters And I want this operation cheap. Currently my table is hosting in Postgres 7, on a single 16G memory Box, and I would love to see some good suggestion for me to host this in low cost and also allow me to scale up for performance if needed. The table serves: 1. Query: 90% 2. Insert: 9.9% 2. Update: 0.1% <-- very rare.

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  • Automated Java to Scala source code conversion?

    - by Alex R
    (Yes I know I can call Java code from Scala; but that is pointless; I want to DELETE the Java code, not keep it around and have to look at it and maintain it forever!) Are there any utilities out there to convert Java source to Scala source? I believe theoretically it should be possible to accomplish with minimal lossage. I have found this but it seems inactive, probably buggy/incomplete... http://sourceforge.net/projects/java2scala/ Any alternatives?

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  • Why should GoTos be bad?

    - by lisn
    I'm using gotos and a lot of them. C++, PHP or COBOL - I use them on nearly all occasions where everybody else would use functions or even classes. Yet my code is Clear Maintainable Bug-free Fast So why does everybody I meet tell me about how bad gotos are? Are there any facts that show that they are "bad"?

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  • Events and references pattern

    - by serhio
    In a project I have the following relation between BO and GUI By e.g. G could represent a graphic with time lines, C a TimeLine curve, P - points of that curve and T the time that represents each point. Each GUI object is associated with the BO corresponding object. When T changes GUI P captures the Changed event and changes its location. So, when G should be modified, it modifies internally its objects and as result T changes, P moves and the GuiG visually changes, everything is OK. But there is an inconvenient of this architecture... BO should not be recreated, because this will breack the link between BO and GUIO. In particular, GUI P should always have the same reference of T. If in a business logic I do by e.g. P1.T = new T(this.T + 10) GUI_P1 will not move anymore, because it wait an event from the reference of former P1.T object, that does not belongs to P1 anymore. So the solution was to always modify the existing objects, not to recreate it. But here is an other inconvenient: performance. Say I have a ready newC object that should replace the older one. Instead of doing G1.C = newC I should do foreach T in foreach P in C replace with T from P from newC. Is there an other more optimal way to do it?

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