A methodology that enables a system to be modeled as a set of objects that can be controlled and manipulated in a modular manner

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2answers
213 views

Can an object call a method on it's immediate descendant? [closed]

I have an inheritance hierarchy three deep : an abstract base class, from which I derive another abstract class, call it the intermediate class, from which will derive possibly a large variety of ...
5
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5answers
577 views

Should I always encapsulate an internal data structure entirely?

Please consider this class: class ClassA{ private Thing[] things; // stores data // stuff omitted public Thing[] getThings(){ return things; } } This class exposes the ...
3
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3answers
173 views

Understanding UML composition better

The difference between Composition and Aggregation in UML (and sometimes in programming too) is that with Composition, the lifetime of the objects composing the composite (e.g. an engine and a ...
4
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3answers
327 views

Inheritance vs containment while extending a large legacy project

I have got a legacy Java project with a lot of code. The code uses MVC pattern and is well structured and well written. It also has a lot of unit tests and it is still actively maintained (bug fixing, ...
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0answers
74 views

Is this considered an implementation of the Template Method design pattern?

Please consider a StringBank class. This class holds a list of Strings and can return them to the client. It's code (irrelevant stuff omitted): abstract class StringBank{ List<String> ...
1
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1answer
89 views

How to properly handle conditional dependencies in a factory?

Let's say you have a string $action run-time, that specifies which type of $object needs to be created: $dbobject, $memcacheobject, $fileobject, $xmlobject, etc. Assume also, that creation of an ...
3
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1answer
156 views

Does this Decorator implementation violate the Liskov Substitution Principle?

Please consider the following implementation of the Decorator design pattern: WordBank objects store strings and return them to the client through the method getWords(). The decorator class, ...
1
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2answers
150 views

Three variants of circular references between objects: how to choose?

I'm designing an object dependency graph of my program and one ambiguity between design variants appears from time to time. Imagine two objects having a reference to each other. Obviously, at least ...
5
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1answer
583 views

Is this actually good OO design?

Context I have Specification class with several properties including: StartDate, EndDate, DaysToComplete, DateToComplete. A specification contains a list of required courses (i.e. a company requires ...
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4answers
186 views

Why encapsulate container variables? [duplicate]

I wasn't sure how to formulate the title, but there's something that's made little sense to me in OOP I understand the idea of encapsulation, which is to create a layer of protection, and ...
2
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0answers
115 views

How does a search functionality fit in DDD with CQRS?

In Vaughn Vernon's book Implementing domain driven design and the accompanying sample application I found that he implemented a CQRS approach to the iddd_collaboration bounded context. He presents ...
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4answers
248 views

Why is Java not 'pure' OOP? [duplicate]

Java is designed in a very OO approach, and somewhat even 'forces' programmers to program within the OO paradigm (which can be considered good or bad, a matter of opinion). However while almost ...
0
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7answers
345 views

Using a Simple/Static Factory vs. instantiating directly: new Thing() vs. factory.createThing() - what's the benefit?

Here are two ways to instantiate an object: Option 1: Thing thing = new Thing(); Option 2: (the factory is a Static Factory, but it could also be a Simple Factory). Thing thing = ...
2
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1answer
127 views

Calling static method from instance of class

As a developer I am fan of static methods. Recently I come across difference between OOP languages about this static methods. All OOP language use static method to access any method without ...
0
votes
1answer
46 views

Restricting object types that can be added to each other using the Composite Pattern

The Situation: I am building a custom PHP application framework. I have implemented a composite pattern so I can build a object tree representing the page to be rendered. Example: abstract class ...
-4
votes
1answer
110 views

How is the Decorator Pattern actually used in practice? [closed]

I understand completely how to implement the Decorator pattern, and I also understand what it's intent is. The Decorator is used in one of two cases: As an alternative to subclassing - when there ...
0
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0answers
54 views

Import data and modify

I should build an importer in PHP. So below you can see how it should work or how it currently works. This is only a small example, the real importer is much bigger so the import() method is also ...
0
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1answer
233 views

Many-to-many in OOP: Class A instantiates Class B, which instantiates Class A, which

I am mapping Field1 to Field2. The map object instantiates the field object and vice versa, creating an infinite loop. This is in PHP. class field { protected $maps; // mapCollection object. all ...
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2answers
186 views

I'm not sure how to add common functionality to my business objects using DTOs/DDD? [closed]

I have created a couple of projects to create a better division of my code: I have a Portable Class Library targeting all frameworks that contains just basic DTOs (auto-generated against a database). ...
1
vote
1answer
109 views

From a DDD perspective is a report generating service a domain service or an infrastructure service?

Let assume we have the following service whose responsibility is to generate Excel reports: class ExcelReportService{ public String generateReport(String fileFormatFilePath, ResultSet data){ ...
6
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3answers
275 views

How to adhere to the open-closed principle in practice

I understand the intent of the open-closed principle. It's meant to reduce the risk of breaking something that already works while modifying it, by telling you to try to extend without modifying. ...
15
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1answer
544 views

How to effectively cooperate in a team having mixed background/mindset regarding OOP? [duplicate]

I've been recently assigned for a new high-performance C++ project (finance) together with 3 other guys who, like, me, refer to themselves as "primarily C/C++ programmers", meaning, all of us have ...
1
vote
1answer
78 views

Using a list of tuples vs a list of custom objects

I have a situation where I have several text documents and I want to create a list that contains the words in those documents. But I also need to record several properties of each word. These ...
2
votes
1answer
91 views

What's the right OO way to create a counter/inventory class that works for both differentiated and undifferentiated countables?

You are writing a videogame about trading beans. Red beans, black beans, pinto beans, you name it. As everybody knows all beans are the same. You write the "Inventory" class for a trader in that ...
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3answers
94 views

How to divide OO project into packages?

I'm a hobbyist programmer working on my own projects. I use Java. Until recently my average project was only 1000 LoC. My latest project however is bigger and is starting to exceed 1500 LoC. I ...
3
votes
4answers
214 views

Why is there no 'subclasses-only' access modifier in Java?

In Java, there are four available access modifiers for methods: public - any class can use this method. protected - classes in the same package and subclasses in any package can use this method. ...
3
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1answer
87 views

Object-Oriented Object Transformations

At my company, we are considering rewriting our business logic and database to have a better architecture after years of organic and unforeseen growth, leading to the inevitable maintenance nightmare. ...
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2answers
544 views

How exactly to use the MVC design pattern

I have read the documentation on the apple's developer website which refer following guidelines A view class shouldn't depend on a model class (although this may be unavoidable with some custom ...
2
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2answers
208 views

What do I gain by using the Strategy pattern in this case?

I wrote a program with Java that plays simple music. Currently chords have only one way ('strumming pattern') to be played. I want to expand this and create different 'strumming patterns' that chords ...
3
votes
6answers
286 views

Do you have to have boxing of primitives in OO language?

Is boxing of primitives required in OO languages to keep them consistent with the rest of the object system (generics etc.)? Or is it avoidable - is it possible to avoid any additional performance ...
1
vote
3answers
105 views

Reason to treat internal class variables and functions inside a class as “separate” entities

Note: there is a similar question that addresses my subject: Better style for member variables? ... but that question does not address "dealing with large legacy code base and comprehension of ...
0
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1answer
73 views

MVC: Where should I store interchangeable algorithms used by the Model (whose names also need to be accessible to the View)?

Please consider a program, where the user chooses an algorithm from a list, and the Strategy pattern is utilized to set this algorithm as the model's operation. For example, an image procession ...
6
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2answers
440 views

MVC: my controller seems useless half of the time. Is this a problem?

Often when I design a program with MVC, the controller is useless half of the time. What I mean is this: something happens on the view (e.g. a button click). The view then notifies the controller. ...
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2answers
237 views

Can I create a query which allows me to do this?

I have a table which stores user information, one column stores their ID. I had implemented four different attributes in the same table which stored a bit indicating which file operations that user ...
0
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2answers
162 views

Is often using int constants as parameters in communication between objects considered bad design?

An app I'm working on is designed with MVC. The components often interacts with each other by passing int constants, which then have to be interpreted with if statements. I'm wondering if this is ...
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4answers
130 views

Dealing with similar objects with different method signatures

I am fairly new to OO design and have problems with the design of some software and looking for a pattern or a combination of patterns that could help me solving my problem. I have a type that has a ...
2
votes
3answers
185 views

Should data models know where / how they're stored?

I have some classes that represent, for the most part, data that's deserialized from XML. They also have some behavior in them, because I don't want to suffer from an anemic domain model. These domain ...
2
votes
1answer
90 views

Interface hierarchy design for separate domains

There are businesses and people. People could be liked and businesses could be commented on: class Like class Comment class Person implements iLikeTarget class Business implements iCommentTarget ...
0
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2answers
80 views

High-Level Classes and Low-Level Classes [duplicate]

I've seen at SOLID there is a principle Dependency inversion principle. Also I've seen that: High-level Classes should not depend on Low-level Classes but both of them should depend on abstractions. ...
7
votes
3answers
349 views

Object Identity and Mutability

I was reading a proposal for value types in Java, and I came across this sentence: "Object identity serves only to support mutability, where an object’s state can be mutated but remains the same ...
4
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4answers
394 views

MVC: Does the Controller break the Single Responsibility Principle?

The Single Responsibility Principle states that "a class should have one reason the change". In the MVC pattern, the Controller's job is to mediate between the View and the Model. It offers an ...
2
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2answers
113 views

MVC: Controller often simply delegates to Model when notified by View of GUI events. Is this reasonable?

Since I learnt about MVC, I used it for every app I made (which is arguably not the best idea, but that's not the topic of this question). All of them small, 1000 LoC apps. I am using Java and Swing ...
2
votes
3answers
194 views

Should POCO domain classes contain collections?

The question title is not good, but I couldn't think of a way to word it better. I am used to develop using POCO classes in my projects, that is, domain objects contain absolutely no logic, only ...
1
vote
2answers
274 views

Classes shouldn't call other classes? [closed]

I've just finished reading The Art of Unit Testing, by Roy Osherove. It was an interesting book, but I'm having trouble with something he mentions near the end (section 11.2.2): Identifying ...
2
votes
2answers
105 views

How to (or should I) have one assert per test with object comparisons? [duplicate]

I've recently read The Art of Unit Testing by Roy Osherove which I found very useful for helping me establish how to define a good unit test. One key aspect of the guidelines Roy puts forward are to ...
0
votes
2answers
128 views

Interface method signature not restrictive enough

I wrote a piece of code at my job sometime ago. While writting the code I wrote few interfaces who would allow me to add more flexibility and at that time I was also trying to understand OOP concept ...
1
vote
1answer
169 views

Practical programming according to the Dependency Inversion Principle

What the Dependency Inversion Priciple implies in practice is that in a system, high level components should depend on abstractions of the low level components (instead of on the low level components ...
0
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1answer
78 views

Persisting type in Java - should I be using flags?

Is there some specific piece of advice around persist values that indicate type? Specifically I want to know if I should persist a flag/state indicating the type in persistence or not. I get the ...
3
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2answers
97 views

UML class diagram: how to annotate observer-subject relationship?

How can I annotate in a UML class diagram that an instance of ClassA is registered as an observer of an instance of ClassB? (Both implement the appropriate interfaces). This doesn't really belong in ...
1
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4answers
502 views

Is it considered 'reasonable' to implement a major part of a program largely by subclassing a library class? [closed]

I'm planning to implement a word processor using Java, and Swing for the GUI. I was thinking how I can implement the text area where the user types the text. My idea was to subclass JTextArea. It ...