On Wed, Jun 11, 2008 at 12:02 AM, Larry Garfield <larry@xxxxxxxxxxxxxxxx> wrote: > On Tuesday 10 June 2008, Shelley wrote: > > Hi all, > > > > If you are designing with OO principles, could you give an explanation of > > what is the difference classes and packages? > > > > Several principles talks about classes and packages, such as: > > The classes in a package are reused together. If you reuse one of the > > classes in a package, you reuse them all. > > > > but few explains the difference between them. > > > > When I was summarizing the OO principles, that question confused me: > > > http://phparch.cn/index.php/php/43-php-advanced-programming/170-principles- > >of-object-oriented-design > > > > Thanks in advance. :) > > A class is a syntactic way of grouping behavior and data together in an > encapsulated fashion (at least that's the PHP definition). > > A formal package is a syntactic way of grouping related classes together, > either for easier distribution, somewhat tighter coupling, or syntactic > sugar. For instance, you could have 5 classes that make up your "Database > abstraction" package; they're all discrete, but all work in concert. > > PHP does not have a syntactic "package" concept. The closest thing would > be > namespaces as implemented in PHP 5.3, but that's not out yet. Many systems > emulate packages with verbose class naming (eg, Database_Connection, > Database_Query, Database_Transaction, Database_Query_Select, etc.), but I > personally find that ugly. :-) furthermore, in languages such as java (and likely others) packages have access levels which are conceptually similar to ppp in classes. this allows designers to limit access to certain classes in a given package (duh); it turns out to be quite useful. imagine you are a library author and some of the classes you distribute, you dont intend for your clients to use, well then, you simply mark those classes as private. i dont believe the php namespace concept incorporates this feature, nor do i think its really relevant, in a source based language. however, i do find it relevant to the discussion ;D -nathan
