Object Concepts <ul><li>Object-oriented software   </li></ul><ul><li>Objects  </li></ul><ul><li>Messages  </li></ul><ul><l...
<ul><li>Classes and protocols   </li></ul><ul><li>Initial state of an object  </li></ul><ul><li>Objects of different class...
<ul><li>Message arguments  </li></ul><ul><li>Keyword messages and arguments  </li></ul><ul><li>Message selectors  </li></u...
New concepts <ul><li>An object is able to find out about its own state. </li></ul><ul><li>The initial state of an object h...
<ul><li>The class description is a template for its members, so that each member has </li></ul><ul><li>the same attributes...
Protocols <ul><li>The protocol described by a class is the set of messages understood by the member objects. </li></ul><ul...
Objects <ul><li>Object-oriented software consists of  objects  that communicate by sending messages to each other. The use...
Messages and attributes <ul><li>In an object-oriented application, each action is achieved by sending a message to an obje...
A class <ul><li>A class ensures that all instances it creates have the same attributes and respond to the same set of mess...
Upcoming SlideShare
Loading in …5
×

Object Concepts Chapter 6

371 views

Published on

Published in: Technology
1 Comment
0 Likes
Statistics
Notes
  • NO SIN CARD INSTALLED<br /><br/>
       Reply 
    Are you sure you want to  Yes  No
    Your message goes here
  • Be the first to like this

No Downloads
Views
Total views
371
On SlideShare
0
From Embeds
0
Number of Embeds
28
Actions
Shares
0
Downloads
7
Comments
1
Likes
0
Embeds 0
No embeds

No notes for slide

Object Concepts Chapter 6

  1. 1. Object Concepts <ul><li>Object-oriented software </li></ul><ul><li>Objects </li></ul><ul><li>Messages </li></ul><ul><li>Attributes and state </li></ul><ul><li>Sending messages </li></ul><ul><li>Using messages to make objects do things </li></ul><ul><li>Grouping objects into classes </li></ul><ul><li>Grouping messages into a protocol </li></ul><ul><li>Attributes of a software object </li></ul><ul><li>Messages that do not alter an objects state </li></ul><ul><li>Inspecting state using an inspector </li></ul>
  2. 2. <ul><li>Classes and protocols </li></ul><ul><li>Initial state of an object </li></ul><ul><li>Objects of different classes </li></ul><ul><li>Classes and writing software </li></ul><ul><li>Polymorphism </li></ul><ul><li>Classes and subclasses </li></ul><ul><li>State-dependent behavior </li></ul><ul><li>Subclasses </li></ul><ul><li>Programming and subclasses </li></ul>
  3. 3. <ul><li>Message arguments </li></ul><ul><li>Keyword messages and arguments </li></ul><ul><li>Message selectors </li></ul><ul><li>More than one argument in a message </li></ul><ul><li>Message answers, enquiry messages and collaborating </li></ul><ul><li>objects </li></ul><ul><li>Enquiry messages and message answers </li></ul><ul><li>Collaborating objects </li></ul>
  4. 4. New concepts <ul><li>An object is able to find out about its own state. </li></ul><ul><li>The initial state of an object has to be prescribed. </li></ul><ul><li>A class groups together objects with the same characteristics (the same </li></ul><ul><li>attributes and potential behavior). When programming, a class is used to define how objects (‚instances) of the class will be created. </li></ul><ul><li>One class description serves to describe all the objects of that class Œ the information each can hold and the set of messages to which each can respond. </li></ul>
  5. 5. <ul><li>The class description is a template for its members, so that each member has </li></ul><ul><li>the same attributes to hold information and responds to the same messages with the same resultant behavior. </li></ul><ul><li>The ‚state of an object is a set of values representing the attributes of objects of a given class. </li></ul>
  6. 6. Protocols <ul><li>The protocol described by a class is the set of messages understood by the member objects. </li></ul><ul><li>The same message sent to objects of different classes may provoke a different behaviour in each class. </li></ul><ul><li>A class may have a subclass. </li></ul><ul><li>Every message has a message answer. </li></ul><ul><li>Message answers may be used in collaborations between objects. </li></ul>
  7. 7. Objects <ul><li>Object-oriented software consists of objects that communicate by sending messages to each other. The user can also communicate with an object by sending it a message via a user interface. </li></ul><ul><li>Objects represent the components of a Smalltalk system such as the numbers, files and processes. Messages represent the interactions between the components of a Smalltalk system for example, arithmetic, file creation and text manipulation. </li></ul>
  8. 8. Messages and attributes <ul><li>In an object-oriented application, each action is achieved by sending a message to an object. </li></ul><ul><li>In order to carry out the action requested by a received message, an object may need to hold information. Different kinds of object hold different kinds of information called attributes </li></ul>
  9. 9. A class <ul><li>A class ensures that all instances it creates have the same attributes and respond to the same set of messages in an identical manner. </li></ul><ul><li>understand the same messages; </li></ul><ul><li>respond in the same way to each message; </li></ul><ul><li>have the same attributes. </li></ul>

×