Specification pattern: Difference between revisions

Revision as of 04:54, 10 September 2016

Revision as of 03:38, 24 September 2016

Line 287:

<source lang="csharp">

OverDueSpecificationvar OverDue = new OverDueSpecification();

NoticeSentSpecificationvar NoticeSent = new NoticeSentSpecification();

InCollectionSpecificationvar InCollection = new InCollectionSpecification();

// example of specification pattern logic chaining

ISpecification<Invoice>var SendToCollection = OverDue.And(NoticeSent).And(InCollection.Not());

var InvoiceCollection = Service.GetInvoices();

foreach (Invoicevar currentInvoice in InvoiceCollection) {

if (SendToCollection.IsSatisfiedBy(currentInvoice)) {

currentInvoice.SendToCollection();

Line 303:

</source>

== Criticisms ==

Contrast without the Specification Pattern:

The Specification Pattern could be considered a software [[Anti-pattern|Anti-Pattern]]:

* [[Cargo cult programming|Cargo Cult Programming]] - There lacks a well-defined purpose for this pattern, and there's no guide when to implement it or not. Also, see [[Law of the instrument]].

* [[Inner-platform effect]] - And() function which directly replicate [[&&]] in [[C#]]. Also, Not() and potentially more. Also, see [[Reinventing the wheel|Reinventing the square wheel]].

* [[Spaghetti code#Lasagna code|Spaghetti/Lasagna Code]] - Separate classes for each part of the specification fragments what could be a cohesive object. In the example above, OverDue is an extra layer between the Logic for SendToCollection and the OverDueSpecification implementation.

Most natural programming languages can accommodate ___domain-driven design with the core Object Oriented concepts.

ContrastAlternative example, without the Specification Pattern:

<source lang="csharp">

var InvoiceCollection = Service.GetInvoices();

foreach (Invoice currentInvoice in InvoiceCollection) {

currentInvoice.SendToCollectionIfNecessary();

Line 321 ⟶ 328:

this.SendToCollection();

}

</source>This alternative uses foundation concepts of Get-Only Properties, Condition-Logic, and Functions. The key alternative here is Get-Only Properties, which are well-named to maintain the Domain-Driven language, and enable the continued use of the natural && operator, instead of the Specification Pattern's And() function. Furthermore, the creation of a well-named function SendToCollectionIfNecessary is potentially more useful and descriptive, than the previous example (which could also be contained in such a function, except not directly on the object apparently).

</source>

==References==