Elements of Design Patterns Example: Iterator Pattern Iterator
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Capturing Interactions in Architectural Patterns
Capturing Interactions in Architectural Patterns Dharmendra K Yadav Rushikesh K Joshi Department of Computer Science and Engineering Department of Computer Science and Engineering Indian Institute of Technology Bombay Indian Institute of Technology Bombay Powai, Mumbai 400076, India Powai, Mumbai 400076, India Email: [email protected] Email: [email protected] TABLE I Abstract—Patterns of software architecture help in describing ASUMMARY OF CCS COMBINATORS structural and functional properties of the system in terms of smaller components. The emphasis of this work is on capturing P rimitives & Descriptions Architectural the aspects of pattern descriptions and the properties of inter- Examples Significance component interactions including non-deterministic behavior. Prefix (.) Action sequence intra-component Through these descriptions we capture structural and behavioral p1.p2 sequential flow specifications as well as properties against which the specifications Summation (+) Nondeterminism choice within a component are verified. The patterns covered in this paper are variants of A1 + A2 Proxy, Chain, MVC, Acceptor-Connector, Publisher-Subscriber Composition (|) Connect matching multiple connected and Dinning Philosopher patterns. While the machines are CCS- A1 | A2 i/o ports in assembly components based, the properties have been described in Modal µ-Calculus. Restriction (\) Hiding ports from Internal The approach serves as a framework for precise architectural A\{p1, k1, ..} further composition features descriptions. Relabeling ([]) Renaming of ports syntactic renaming A[new/old, ..] I. INTRODUCTION In component/connector based architectural descriptions [6], [13], components are primary entities having identities in the represents interface points as ports uses a subset of CSP for system and connectors provide the means for communication it’s formal semantics. -
Automatic Verification of Java Design Patterns
Automatic Verification of Java Design Patterns Alex Blewitt, Alan Bundy, Ian Stark Division of Informatics, University of Edinburgh 80 South Bridge, Edinburgh EH1 1HN, UK [email protected] [email protected] [email protected] Abstract 2. Design patterns There are a number of books which catalogue and de- Design patterns are widely used by object oriented de- scribe design patterns [4, 1, 6] including an informal de- signers and developers for building complex systems in ob- scription of the key features and examples of their use. ject oriented programming languages such as Java. How- However, at the moment there are no books which attempt ever, systems evolve over time, increasing the chance that to formalise these descriptions, possibly for the following the pattern in its original form will be broken. reasons: We attempt to show that many patterns (implemented in Java) can be verified automatically. Patterns are defined 1. The implementation (and description) of the pattern is in terms of variants, mini-patterns, and constraints in a language-specific. pattern description language called SPINE. These specifi- 2. There are often several ways to implement a pattern cations are then processed by HEDGEHOG, an automated within the same language. proof tool that attempts to prove that Java source code 3. Formal language descriptions are not common within meets these specifications. the object oriented development community. Instead, each pattern is presented as a brief description, and an example of its implementation and use. Designers and developers are then expected to learn the ‘feel’ of a pat- 1. -
One-Slide Summary Lecture Outline
Using Design Patterns #1 One-Slide Summary • Design patterns are solutions to recurring OOP design problems. There are patterns for constructing objects, structuring data, and object behavior . • Since this is PL, we’ll examine how language features like (multiple) inheritance and dynamic dispatch relate to design patterns. #2 Lecture Outline • Design Patterns • Iterator • Observer • Singleton • Mediator #3 1 What is a design pattern? • A solution for a recurring problem in a large object-oriented programming system – Based on Erich Gamma’s Ph.D. thesis, as presented in the “gang of four” book • “Each pattern describes a problem which occurs over and over again in our environment, and then describes the core of the solution to that problem, in such a way that you can use this solution a million times over, without ever doing it the same way twice” – Charles Alexander #4 Types of design patterns • Design patterns can be (roughly) grouped into three categories: • Creational patterns – Constructing objects • Structural patterns – Controlling the structure of a class, e.g. affecting the API or the data structure layout • Behavioral patterns – Deal with how the object behaves #5 Iterator design pattern • Often you may have to move through a collection – Tree (splay, AVL, binary, red-black, etc.), linked list, array, hash table, dictionary, etc. • Easy for arrays and vectors • But hard for more complicated data structures – Hash table, dictionary, etc. • The code doing the iteration should not have to know the details of the data structure -
Object-Oriented Analysis, Design and Implementation
Undergraduate Topics in Computer Science Brahma Dathan Sarnath Ramnath Object-Oriented Analysis, Design and Implementation An Integrated Approach Second Edition Undergraduate Topics in Computer Science Undergraduate Topics in Computer Science (UTiCS) delivers high-quality instruc- tional content for undergraduates studying in all areas of computing and information science. From core foundational and theoretical material to final-year topics and applications, UTiCS books take a fresh, concise, and modern approach and are ideal for self-study or for a one- or two-semester course. The texts are all authored by established experts in their fields, reviewed by an international advisory board, and contain numerous examples and problems. Many include fully worked solutions. More information about this series at http://www.springer.com/series/7592 Brahma Dathan • Sarnath Ramnath Object-Oriented Analysis, Design and Implementation An Integrated Approach Second Edition 123 Brahma Dathan Sarnath Ramnath Department of Information and Computer Department of Computer Science Science and Information Technology Metropolitan State University St. Cloud State University St. Paul, MN St. Cloud, MN USA USA Series editor Ian Mackie Advisory Board Samson Abramsky, University of Oxford, Oxford, UK Karin Breitman, Pontifical Catholic University of Rio de Janeiro, Rio de Janeiro, Brazil Chris Hankin, Imperial College London, London, UK Dexter Kozen, Cornell University, Ithaca, USA Andrew Pitts, University of Cambridge, Cambridge, UK Hanne Riis Nielson, Technical University of Denmark, Kongens Lyngby, Denmark Steven Skiena, Stony Brook University, Stony Brook, USA Iain Stewart, University of Durham, Durham, UK A co-publication with the Universities Press (India) Private Ltd., licensed for sale in all countries outside of India, Pakistan, Bhutan, Bangladesh, Sri Lanka, Nepal, The Maldives, Middle East, Malaysia, Indonesia and Singapore. -
Co-Occurrence of Design Patterns and Bad Smells in Software Systems
XI Brazilian Symposium on Information System, Goi^ania,GO, May 26-29, 2015. Co-Occurrence of Design Patterns and Bad Smells in Software Systems: An Exploratory Study Bruno Cardoso Eduardo Figueiredo Software Engineering Lab (LabSoft) Software Engineering Lab (LabSoft) Federal University of Minas Gerais (UFMG) Federal University of Minas Gerais (UFMG) Belo Horizonte, MG - Brazil Belo Horizonte, MG - Brazil [email protected] [email protected] ABSTRACT In a previous work [1], we performed a systematic literature A design pattern is a general reusable solution to a recurring review in order to understand how studies investigate these two problem in software design. Bad smells are symptoms that may topics, design patterns and bad smells, together. Our results indicate something wrong in the system design or code. showed that, in general, studies have a narrow view concerning Therefore, design patterns and bad smells represent antagonistic the relation between these concepts. Most of them focus on structures. They are subject of recurring research and typically refactoring opportunities. Among these, some tools [3][7][15][17] appear in software systems. Although design patterns represent have been proposed to identify code fragments that can be good design, their use is often inadequate because their refactored to patterns. Other studies [2][6] establish a structural implementation is not always trivial or they may be unnecessarily relationship between the terms design pattern and bad smell. In employed. The inadequate use of design patterns may lead to a addition, there are reported cases in the literature where the use of bad smell. Therefore, this paper performs an exploratory study in design patterns may not always be the best option and the wrong order to identify instances of co-occurrences of design patterns use of a design pattern can even introduce bad smells in code [19] and bad smells. -
Enterprise Development with Flex
Enterprise Development with Flex Enterprise Development with Flex Yakov Fain, Victor Rasputnis, and Anatole Tartakovsky Beijing • Cambridge • Farnham • Köln • Sebastopol • Taipei • Tokyo Enterprise Development with Flex by Yakov Fain, Victor Rasputnis, and Anatole Tartakovsky Copyright © 2010 Yakov Fain, Victor Rasputnis, and Anatole Tartakovsky.. All rights reserved. Printed in the United States of America. Published by O’Reilly Media, Inc., 1005 Gravenstein Highway North, Sebastopol, CA 95472. O’Reilly books may be purchased for educational, business, or sales promotional use. Online editions are also available for most titles (http://my.safaribooksonline.com). For more information, contact our corporate/institutional sales department: (800) 998-9938 or [email protected]. Editor: Mary E. Treseler Indexer: Ellen Troutman Development Editor: Linda Laflamme Cover Designer: Karen Montgomery Production Editor: Adam Zaremba Interior Designer: David Futato Copyeditor: Nancy Kotary Illustrator: Robert Romano Proofreader: Sada Preisch Printing History: March 2010: First Edition. Nutshell Handbook, the Nutshell Handbook logo, and the O’Reilly logo are registered trademarks of O’Reilly Media, Inc. Enterprise Development with Flex, the image of red-crested wood-quails, and related trade dress are trademarks of O’Reilly Media, Inc. Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and O’Reilly Media, Inc. was aware of a trademark claim, the designations have been printed in caps or initial caps. While every precaution has been taken in the preparation of this book, the publisher and authors assume no responsibility for errors or omissions, or for damages resulting from the use of the information con- tained herein. -
Design Patterns Design Patterns
Design Patterns CSC207 – Software Design Design Patterns • Design pattern: – A general description of the solution to a well- established problem using an arrangement of classes and objects. • Patterns describe the shape of code rather than the details. – There are lots of them in CSC 301 and 302. Loop patterns from first year • Loop pattern: – A general description of an algorithm for processing items in a collection. • All of you (hopefully) have some loop patterns in your heads. • You don’t really need to think about these any more; you just use them, and you should be able to discuss them with your fellow students. • Some first-year patterns: – Process List – Counted Loop – Accumulator – Sentinel Process list pattern • Purpose: to process every item in a collection where you don’t care about order or context; you don’t need to remember previous items. • Outline: • Example: • Other example: darken every pixel in a picture Counted loop pattern • Purpose: to process a range of indices in a collection. • Outline: • Example: • Other example: print indices of even-length string Accumulator pattern • Purpose: to accumulate information about items in a collection. • Outline: • Example: • Other examples: sum, min, accumulate a list of items meeting a particular criterion. Sentinel pattern • Purpose: to remove a condition in a loop guard. • Outline: • Example: Sentinel pattern, continued • Here is the code that Sentinal replaces; note that i != list.size() is evaluated every time through the loop, even though it is false only once. Design Pattern -
Behavioral Patterns
Behavioral Patterns 101 What are Behavioral Patterns ! " Describe algorithms, assignment of responsibility, and interactions between objects (behavioral relationships) ! " Behavioral class patterns use inheritence to distribute behavior ! " Behavioral object patterns use composition ! " General example: ! " Model-view-controller in UI application ! " Iterating over a collection of objects ! " Comparable interface in Java !" 2003 - 2007 DevelopIntelligence List of Structural Patterns ! " Class scope pattern: ! " Interpreter ! " Template Method ! " Object scope patterns: ! " Chain of Responsibility ! " Command ! " Iterator ! " Mediator ! " Memento ! " Observer ! " State ! " Strategy ! " Visitor !" 2003 - 2007 DevelopIntelligence CoR Pattern Description ! " Intent: Avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request. Chain the receiving objects and pass the request along the chain until an object handles it. ! " AKA: Handle/Body ! " Motivation: User Interfaces function as a result of user interactions, known as events. Events can be handled by a component, a container, or the operating system. In the end, the event handling should be decoupled from the component. ! " Applicability: ! " more than one object may handle a request, and the handler isn't known a priori. ! " Want to issue a request to one of several objects without specifying the receiver !" 2003 - 2007 DevelopIntelligence CoR Real World Example ! " The Chain of Responsibility pattern avoids coupling the sender of a request to the receiver, by giving more than one object a chance to handle the request. ! " Mechanical coin sorting banks use the Chain of Responsibility. Rather than having a separate slot for each coin denomination coupled with receptacle for the denomination, a single slot is used. When the coin is dropped, the coin is routed to the appropriate receptacle by the mechanical mechanisms within the bank. -
Prof. Catalin Boja, Phd [email protected] Source Code Quality
Design patterns Prof. Catalin Boja, PhD [email protected] http://acs.ase.ro/software-quality-testing Source code quality Principles for writing the code: • Easy to read / understand - clear • Easy to modify - structured • Easy to reuse • Simple (complexity) • Easy to test • Implement patterns for the standard problem Left: Simply Explained: Code Reuse 2009-12- acs.ase.ro [email protected] 03.By Oliver Widder, Webcomics Geek Aad Poke.2 Source code quality Forces that influence it: • Available time (delivery terms) • Costs • The experience of the programmer • Programmer competences • Specifications clarity • Solution complexity • Change rates for specifications, requirements, team, etc http://khristianmcfadyen.com/ acs.ase.ro [email protected] 3 Anti-Pattern: Big ball of mud “A Big Ball of Mud is a haphazardly structured, sprawling, sloppy, duct-tape- and-baling-wire, spaghetti- code jungle.” Brian Foote and Joseph Yoder, Big Ball of Mud, September 1997 acs.ase.ro [email protected] 4 Anti-Pattern: Big ball of mud Where from ? Why ? • Throwaway code - Temporary (Prototyping) solutions to be replaced / rewritten • Cut and Paste code • Adapting code by commenting / deleting other solutions • Very short or unrealistic deadlines • Lack of experience • Lack of standards / procedures acs.ase.ro [email protected] 5 Anti-Pattern: Big ball of mud How do you avoid it? • Rewriting the code (Refactoring) to an acceptable maturity level • Use Clean Code Principles • Design Patterns Implementation acs.ase.ro [email protected] 6 Design-pattern • A pattern is a reusable solution for a standard problem in a given context • Facilitates the reuse of architectures and software design • They are not data structures acs.ase.ro [email protected] 7 Design-pattern “A pattern involves a general “.. -
Reducing Maintenance Costs Through the Application of Modern Software Architecture Principles
Reducing Maintenance Costs Through the Application of Modern Software Architecture Principles Christine Hulse and Michael Ubnoske Louis Vazquez Scott Edgerton Architecture Technology Department of the Army United Defense, LP Minneapolis, Minnesota Picatinny Arsenal, Minneapolis, Minnesota 1.612.829.5864 New Jersey 1.612.572.6109/6156 [email protected] 1.973.724.5259 [email protected] [email protected] [email protected] 1. ABSTRACT 1.1 Keywords Large software programs are usually long lived Architecture, design patterns, software maintenance, modeling, real-time software and continually evolve. Substantial maintenance effort is often extended by 2. INTRODUCTION engineers trying to understand the software The Crusader Field Artillery System is the U.S. Army's next prior to making changes. To successfully generation 155-mm self-propelled howitzer (SPH) and its companion resupply vehicle (RSV). The Crusader is a evolve the software, a thorough understanding software-intensive system that is being designed to last well of the architect's intentions about software into the next century. Ada95 is the implementation language organization is required. Software for all software development on the Crusader program. maintenance costs can be reduced significantly Modern software architecture methods are being applied to if the software architecture is well defined, capture the general principles used throughout the design and to provide a guide for further development of the clearly documented, and creates an software. The architecture is being modeled using the environment that promotes design consistency Unified Modeling Language (UML) to bring together the through the use of guidelines and design design vision of all of the key stakeholders. -
Behavioral Patters
11. Behavioral Pattern Venkat Subramaniam BDP-1 Behavioral Patters • Concerned with algorithms & assignment of responsibilities • Patterns of Communication between Objects Venkat Subramaniam BDP-2 Chain of Responsibility Pattern —Avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request. Chain the receiving objects and pass the request along the chain until an object handles it“ Venkat Subramaniam BDP-3 Example that would benefit from Chain Of Responsibility Pattern • Various types of Controls are used in an application. Controls handle certain events while they do not handle others. Each control may be invoked from other controls. An event not handled by a control must be passed on to its parent control. Venkat Subramaniam BDP-4 Example using Chain of Responsibility Pattern Client Event Handler handleEvent() Control1 Control2 handleEvent() handleEvent() Venkat Subramaniam BDP-5 When to use Chain Of Responsibility Pattern • More than one object may handle a request, and the handler isn‘t known ahead of time. • One of several objects may be the intended receiver • Set of objects that handle request is dynamic Venkat Subramaniam BDP-6 Consequences of using Chain Of Responsibility • Reduced Coupling • Flexibility in assigning responsibilities œ Distributes responsibilities among objects • Receipt isn‘t guaranteed Venkat Subramaniam BDP-7 Chain Of Responsibility Vs. Other Patterns • Often used with Composite œ Parent acts as Successor Venkat Subramaniam BDP-8 Iterator Pattern —Provide -
Scala by Example (2009)
Scala By Example DRAFT January 13, 2009 Martin Odersky PROGRAMMING METHODS LABORATORY EPFL SWITZERLAND Contents 1 Introduction1 2 A First Example3 3 Programming with Actors and Messages7 4 Expressions and Simple Functions 11 4.1 Expressions And Simple Functions...................... 11 4.2 Parameters.................................... 12 4.3 Conditional Expressions............................ 15 4.4 Example: Square Roots by Newton’s Method................ 15 4.5 Nested Functions................................ 16 4.6 Tail Recursion.................................. 18 5 First-Class Functions 21 5.1 Anonymous Functions............................. 22 5.2 Currying..................................... 23 5.3 Example: Finding Fixed Points of Functions................ 25 5.4 Summary..................................... 28 5.5 Language Elements Seen So Far....................... 28 6 Classes and Objects 31 7 Case Classes and Pattern Matching 43 7.1 Case Classes and Case Objects........................ 46 7.2 Pattern Matching................................ 47 8 Generic Types and Methods 51 8.1 Type Parameter Bounds............................ 53 8.2 Variance Annotations.............................. 56 iv CONTENTS 8.3 Lower Bounds.................................. 58 8.4 Least Types.................................... 58 8.5 Tuples....................................... 60 8.6 Functions.................................... 61 9 Lists 63 9.1 Using Lists.................................... 63 9.2 Definition of class List I: First Order Methods..............