Object models strategies patterns and applications Yourdon press company series. Material. Type. Book. Language English. Title. Object models strategies. Book Reviews: Object Models Strategies, Patterns, and Applications, Peter Coad. Full Text: PDF . A multi-threaded object-oriented programming model. Books» » Object Models: Strategies, Pa. Object Models: Strategies, Patterns, and Applications (2nd Edition) pdf by David North Download. Download .
|Language:||English, Spanish, Portuguese|
|Distribution:||Free* [*Sign up for free]|
fines the notion of pattern for object models as "a template of objects with stereotypical pattern for interpreting and understanding an application domain. .. A section on an appropriate development strategy which, in our case, considers. r epolres. Peter Coad. Object-Oriented. Patterns his article explores patterns, Pattern. A fully realized form, original, or model accepted or proposed for imitation: something an overall strategy . . and by observing many applications. Object Models: Strategies, Patterns, and Applications (2nd Edition) [Peter Coad, David North, Mark Mayfield] on podmimokongist.ga *FREE* shipping on qualifying.
Within the Module pattern, variables or methods declared are only available inside the module itself thanks to closure. Variables or methods defined within the returning object however are available to everyone. History From a historical perspective, the Module pattern was originally developed by a number of people including Richard Cornford in It was later popularized by Douglas Crockford in his lectures.
Another piece of trivia is that if you've ever played with Yahoo's YUI library, some of its features may appear quite familiar and the reason for this is that the Module pattern was a strong influence for YUI when creating their components.
Examples Let's begin looking at an implementation of the Module pattern by creating a module which is self-contained. The counter variable is actually fully shielded from our global scope so it acts just like a private variable would - its existence is limited to within the module's closure so that the only code able to access its scope are our two functions.
Our methods are effectively namespaced so in the test section of our code, we need to prefix any calls with the name of the module e. When working with the Module pattern, we may find it useful to define a simple template that we use for getting started with it. The module itself is completely self-contained in a global variable called basketModule. The basket array in the module is kept private and so other parts of our application are unable to directly read it.
It only exists with the module's closure and so the only methods able to access it are those with access to its scope i. Notice how the scoping function in the above basket module is wrapped around all of our functions, which we then call and immediately store the return value of.
This has a number of advantages including: The freedom to have private functions and private members which can only be consumed by our module. As they aren't exposed to the rest of the page only our exported API is , they're considered truly private. Given that functions are declared normally and are named, it can be easier to show call stacks in a debugger when we're attempting to discover what function s threw an exception. J Crowder has pointed out in the past, it also enables us to return different functions depending on the environment.
In the past, I've seen developers use this to perform UA testing in order to provide a code-path in their module specific to IE, but we can easily opt for feature detection these days to achieve a similar goal.
Module Pattern Variations Import mixins This variation of the pattern demonstrates how globals e. This effectively allows us to import them and locally alias them as we wish.
Ben Cherry previously suggested an implementation where a function wrapper is used around module definitions in the event of there being a number of commonalities between modules. In the following example, a library function is defined which declares a new library and automatically binds up the init function to document.
Disadvantages The disadvantages of the Module pattern are that as we access both public and private members differently, when we wish to change visibility, we actually have to make changes to each place the member was used.
We also can't access private members in methods that are added to the object at a later point.
That said, in many cases the Module pattern is still quite useful and when used correctly, certainly has the potential to improve the structure of our application.
Other disadvantages include the inability to create automated unit tests for private members and additional complexity when bugs require hot fixes. It's simply not possible to patch privates. Instead, one must override all public methods which interact with the buggy privates. Developers can't easily extend privates either, so it's worth remembering privates are not as flexible as they may initially appear.
For further reading on the Module pattern, see Ben Cherry's excellent in-depth article on it. The Revealing Module pattern came about as Heilmann was frustrated with the fact that he had to repeat the name of the main object when we wanted to call one public method from another or access public variables.
The result of his efforts was an updated pattern where we would simply define all of our functions and variables in the private scope and return an anonymous object with pointers to the private functionality we wished to reveal as public. It also makes it more clear at the end of the module which of our functions and variables may be accessed publicly which eases readability.
Disadvantages A disadvantage of this pattern is that if a private function refers to a public function, that public function can't be overridden if a patch is necessary.
This is because the private function will continue to refer to the private implementation and the pattern doesn't apply to public members, only to functions. Public object members which refer to private variables are also subject to the no-patch rule notes above. As a result of this, modules created with the Revealing Module pattern may be more fragile than those created with the original Module pattern, so care should be taken during usage.
The Singleton Pattern The Singleton pattern is thus known because it restricts instantiation of a class to a single object.
Classically, the Singleton pattern can be implemented by creating a class with a method that creates a new instance of the class if one doesn't exist.
In the event of an instance already existing, it simply returns a reference to that object. Singletons differ from static classes or objects as we can delay their initialization, generally because they require some information that may not be available during initialization time.
They don't provide a way for code that is unaware of a previous reference to them to easily retrieve them. This is because it is neither the object or "class" that's returned by a Singleton, it's a structure.
The master component distributes the work among identical slave components, and computes a final result from the results which the slaves return. Usage In database replication, the master database is regarded as the authoritative source, and the slave databases are synchronized to it.
Peripherals connected to a bus in a computer system master and slave drives.
Master-slave pattern 4. Pipe-filter pattern This pattern can be used to structure systems which produce and process a stream of data. Each processing step is enclosed within a filter component. Data to be processed is passed through pipes. These pipes can be used for buffering or for synchronization purposes. Usage Compilers. The consecutive filters perform lexical analysis, parsing, semantic analysis, and code generation.
Workflows in bioinformatics. Pipe-filter pattern 5. These components can interact with each other by remote service invocations. A broker component is responsible for the coordination of communication among components. Servers publish their capabilities services and characteristics to a broker. Clients request a service from the broker, and the broker then redirects the client to a suitable service from its registry.