Design Patterns: The Registry Pattern (Atlanta PHP February 2009)

Transcript

1. Design Patterns:
   The Registry Pattern Ben Ramsey Atlanta PHP •

   5 Feb 2009

2. What Is a Design Pattern? “A design pattern is a

   general reusable solution to a commonly occurring problem in software design. ...”

3. What Is a Design Pattern? “... A design pattern is

   not a finished design that can be transformed directly into code. It is a description or template for how to solve a problem that can be used in many different situations.” -- Wikipedia

4. Patterns We’ve Discussed • Singleton • Factory

5. Registry Pattern • Application data store • Acts as a

   “dictionary” of name/value pairs of data • Can contain scalars, arrays, objects, etc. • Pass it around to have a more-or-less “global” data store; sensitive to scope
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8. Example Usage

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10. The downside (or upside) is you have to pass the

    Registry object around.

11. Singleton Registry • The store itself is a singleton •

    Truly “global” data store • No need to pass registry around, exists in all scopes
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14. Example Usage

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16. Criticism • The Registry is a kind of global variable;

    global variables create code smell • Martin Fowler advocates the use of static methods for the Registry; this creates mixed feelings in developer communities