Post on 16-Jul-2015
Principles of Package DesignHow to create cohesive, stable packages
Matthias Noback - Noback's OfficeFOSDEM - 1 Feb 2015
A Year With Symfony
leanpub.com/a-year-with-symfony
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Tight couplingCoupling to a framework
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Code
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PackagesThere are many different kinds
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Class design
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Package designNothing?
butunclebob.com
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Principles of Package Design
leanpub.com/principles-of-package-design
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Package designCohesion
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Package designCoupling
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A - Cohesion principlesPerspective: the package in isolation
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1 - The Release Reuse Equivalence PrincipleThe granule of reuse is the granule of release
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1 - The Release Reuse Equivalence Principle
Version control and hostingComposer package definitionMeta-filesAuto-loading
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Semantic versioning
Quality control
·BranchesTagsBackward compatibility
---
·
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1 - The Release Reuse Equivalence Principle
If you don't have the time to turn your reusable code into a proper package...
Don't release it.
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2- The Common Reuse PrincipleClasses that are used together are packaged together
If you use one class of a package,you will use all its other classes too.
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2- The Common Reuse PrincipleSmell: Feature strata
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2- The Common Reuse PrincipleExample of feature strata: the Symfony Security Component
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2- The Common Reuse PrincipleSmell: Classes with different dependencies
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2- The Common Reuse PrincipleExample of different dependencies: Gaufrette
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2- The Common Reuse PrincipleDifferent dependencies: Gaufrette
{
"name": "knplabs/gaufrette",
...
"suggest": {
"knplabs/knp-gaufrette-bundle": "to use with Symfony2",
"dropbox-php/dropbox-php": "to use the Dropbox adapter",
"rackspace/php-opencloud" : "to use Opencloud adapter",
"herzult/php-ssh": "to use SFtp adapter",
"phpseclib/phpseclib": "to use PhpseclibSftp adapter",
"aws/aws-sdk-php": "to use the Amazon S3 adapter",
"amazonwebservices/aws-sdk-for-php": "to use the legacy Amazon S3 adapters",
"doctrine/dbal": "to use the Doctrine DBAL adapter",
"microsoft/windowsazure": "to use Microsoft Azure Blob Storage adapter",
"ext-zip": "to use the Zip adapter",
"ext-apc": "to use the APC adapter",
...
},
...
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2 - The Common Reuse PrincipleLeszek Prabucki's response
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3 - The Common Closure PrincipleClasses that change together are packaged together
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3 - The Common Closure PrincipleReasons for change
The application's features changeThe business rules changeThe web framework's best practices changeThe persistence library's configuration changes...
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3 - The Common Closure PrincipleSmell: code for multiple application layers
Web User InterfaceCommand-line interfaceModelInfrastructure services
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B - Coupling principlesPerspective: the package in relation to other packages
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4 - The Acyclic Dependencies PrincipleThe dependency graph of packages must have no cycles
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4 - The Acyclic Dependencies Principle
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Stability
Something is stable if it's resistant to change.
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5 - The Stable Dependencies PrincipleAn irresponsible package
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5 - The Stable Dependencies PrincipleA dependent package
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5 - The Stable Dependencies PrincipleAn instable package: irresponsible and dependent
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5 - The Stable Dependencies PrincipleA responsible package
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5 - The Stable Dependencies PrincipleAn independent package
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5 - The Stable Dependencies PrincipleA stable package: responsible and independent
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5 - The Stable Dependencies PrincipleDepend in the direction of stability
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5 - The Stable Dependencies PrincipleCounter example
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6 - The Stable Abstractions PrincipleWhat is more likely to change?
Something concrete or something abstract?A class or an interface?
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6 - The Stable Abstractions PrincipleAbstractness should increase with stability
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SummaryReuse/release equivalence principle
Common reuse principle
Common closure principle
Acyclic dependencies principle
Stable dependencies principle
Stable abstractions principle
·Reuse only code that you can release as a product.-
·All code in a package is reused at the same time.-
·Code in a package only changes for a few reasons.-
·No cycles in the dependency graph.-
·Only depend on more stable packages.-
·More stable packages are also more abstract.-
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Word of advice
You can't maximize them all at the same time.
Keep them in mind while you are working on a package.
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Principles of Package Design
leanpub.com/principles-of-package-design
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Questions?
twitter @matthiasnoback
feedback joind.in/13057
leanpub leanpub.com/principles-of-package-design
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Image courtesyClean CodersGitHubBitBucketPackagistPoEAABut Uncle BobRobert Martin
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