Group items tagged Patterns - Coders

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Singleton pattern - Wikipedia, the free encyclopedia - 0 views

en.wikipedia.org/...Singleton_pattern singleton-pattern programming

shared by Tarik Guney on 03 Nov 09 -

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the singleton pattern is a design pattern that is used to restrict instantiation of a class to one object.
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Tarik Guney on 03 Nov 09

In software engineering, the singleton pattern is a design pattern that is used to restrict instantiation of a class to one object. This is useful when exactly one object is needed to coordinate actions across the system. The concept is sometimes generalized to systems that operate more efficiently when only one object exists, or that restrict the instantiation to a certain number of objects (say, five). Some consider it an anti-pattern, judging that it is overused, introduces unnecessary limitations in situations where a sole instance of a class is not actually required, and introduces global state into an application.

<div class="cArrow"> </div><div class="cContentInner">In software engineering, the singleton pattern is a design pattern that is used to restrict instantiation of a class to one object. This is useful when exactly one object is needed to coordinate actions across the system. The concept is sometimes generalized to systems that operate more efficiently when only one object exists, or that restrict the instantiation to a certain number of objects (say, five). Some consider it an anti-pattern, judging that it is overused, introduces unnecessary limitations in situations where a sole instance of a class is not actually required, and introduces global state into an application.</div>

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Design Patterns: 15 Years After the Revolution, by Danny Kalev @ InformIT [2009-10-30] - 1 views

www.informit.com/...content.aspx

shared by Fabien Cadet on 01 Nov 09 - No Cached

by defining a description template that included among the rest: Known uses. Sample code (as opposed to a typical algorithm which were often described in plain English and perhaps a few sketchy lines of pseudo-code). Collaboration (A description of how classes and objects used in the pattern interact with each other). Consequences (results and side-effects). Related patterns.
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Would a 2009 catalog of the 23 classic design patterns look much different? According to the authors of Design Patterns: Elements of Reusable Code, the answer is no.
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The authors would reclassify certain patterns and omit a few of the original patterns but the design and implementation would remain pretty much the same: "We have found that the object-oriented design principles and most of the patterns haven't changed since then" says Erich Gamma. You can't escape the feeling that patterns are frozen in time
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In the meantime, in the C++ world the tide has turned towards a completely different paradigm known as generic programming (and to some extent, functional programming). Instead of plain classes and a complex inheritance chain, C++ these days uses templates, meta-programming and static type checking. The C++ Standard Library is the most prominent showpiece of the generic and functional programming idioms.
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Over-engineering is another source of criticism. Programmers who become acquainted with patterns are often tempted to solve every problem using a pattern, even when a much simpler solution would probably be a better choice.
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Design pattern in simple examples @ go4expert.com - 0 views

www.go4expert.com/...showthread.php design patterns toread GoF

shared by Fabien Cadet on 07 Mar 09 - Cached

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Design Patterns in WordPress: We're Just Getting Started - 0 views

wp.tutsplus.com/...ress-were-just-getting-started Development web design programming develop

shared by htmlslicemate.com on 31 May 13 - No Cached

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Iterator Patterns To Traverse Container & Access Element | LINQ - 0 views

technet.weblineindia.com/...-container-access-element-linq Collections Dot Net Foreach IEnumerable IEnumerator Iterator Patterns LINQ

shared by Richard Boss on 27 Mar 14 - No Cached

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Use your singletons wisely - 0 views

www.ibm.com/...co-single.html design patterns singleton

shared by Fabien Cadet on 17 Mar 09 - Cached

I know where you live anti-pattern
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Liskov Substitution Principle
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the easier it is to test a class, the more likely a developer will test it.
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Don't worry: the code will always tell you what to do. Just listen.
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The key points here are that a class is only a singleton if all applications treat it exactly the same and if its clients can use the class without an application context.
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"[c]ode wants to be simple."
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Fabien Cadet on 17 Mar 09

"singletons are unnecessarily difficult to test and may make strong assumptions about the applications that will use them [...] I know where you live anti-pattern [...] Liskov Substitution Principle". "To decide whether a class is truly a singleton: * Will every application use this class exactly the same way? (exactly is the key word) * Will every application ever need only one instance of this class? (ever and one are the key words) * Should the clients of this class be unaware of the application they are part of?"

<div class="cArrow"> </div><div class="cContentInner">"singletons are unnecessarily difficult to test and may make strong assumptions about the applications that will use them [...] I know where you live anti-pattern [...] Liskov Substitution Principle". "To decide whether a class is truly a singleton: * Will every application use this class exactly the same way? (exactly is the key word) * Will every application ever need only one instance of this class? (ever and one are the key words) * Should the clients of this class be unaware of the application they are part of?"</div>

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Pattern Library - dofactory - 0 views

www.dofactory.com/...Patterns.aspx @public code-patterns database develop guidelines/practices

shared by Joel Bennett on 12 Feb 07 - Cached

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Deployment pipeline anti-patterns | Continuous Delivery - 6 views

continuousdelivery.com/...loyment-pipeline-anti-patterns software development deployment pipeline

shared by Fabien Cadet on 09 Jan 11 - No Cached

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GUI Architectures, by Martin Fowler, 2006 - 8 views

www.martinfowler.com/...uiArchs.html GUI coding design patterns MVC MVP article

shared by Fabien Cadet on 01 Apr 13 - Cached

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Partitioning and Layering a Software Application (Examples in C#) - 0 views

www.microsoft.com/...details.aspx development programming csharp design patterns software layers

shared by David Rietz on 16 Jul 10 - Cached

Pattern Library - Hillside - 0 views

www.hillside.net/patterns @public code-patterns database develop guidelines/practices

shared by Joel Bennett on 12 Feb 07 - Cached

MSDN Patterns - 0 views

www.microsoft.com/...patterns.mspx @public code-patterns database develop guidelines/practices

shared by Joel Bennett on 12 Feb 07 - Cached

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Classical Inheritance in JavaScript - 0 views

javascript.crockford.com/inheritance.html javascript inheritance Scripting programming

shared by Matteo Spreafico on 13 Aug 09 - Cached

function ZParenizor2(value) { var that = new Parenizor(value); that.toString = function () { if (this.getValue()) { return this.uber('toString'); } return "-0-" }; return that; }
- Matteo Spreafico on 13 Aug 09
  
  This constructors lies, wondeful!
  
  <div class="cArrow"> </div><div class="cContentInner">This constructors lies, wondeful!</div>
  
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Again, we augment Function. We make an instance of the parent class and use it as the new prototype. We also correct the constructor field, and we add the uber method to the prototype as well.
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This adds a public method to the Function.prototype, so all functions get it by Class Augmentation. It takes a name and a function, and adds them to a function's prototype object.
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To make the examples above work, I wrote four sugar methods. First, the method method, which adds an instance method to a class. Function.prototype.method = function (name, func) { this.prototype[name] = func; return this; };
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JavaScript can be used like a classical language, but it also has a level of expressiveness which is quite unique. We have looked at Classical Inheritance, Swiss Inheritance, Parasitic Inheritance, Class Augmentation, and Object Augmentation. This large set of code reuse patterns comes from a language which is considered smaller and simpler than Java.
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I have been writing JavaScript for 8 years now, and I have never once found need to use an uber function. The super idea is fairly important in the classical pattern, but it appears to be unnecessary in the prototypal and functional patterns. I now see my early attempts to support the classical model in JavaScript as a mistake.
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