Object-oriented Smalltalk, five basic characteristics ① All is subject. ② program is a collection of objects, they have to do to inform each other by sending messages. ③ Each object has its own constituted by other stored objects. (May include by way of an existing object package to create new types of objects.) ④ Each object has its type. All the objects of a particular type ⑤ may receive the same message.
Each object has an interface 1.2
Describes a class with the same characteristics (data elements) and the object behavior (function) is set, it is actually a class of data types.
One of the challenges of object-oriented programming is to create a one to one mapping between objects and solution space of the elements of the problem space
Interface: determined for a particular object request can be issued (To achieve the function). Implementation: meet these requests the code in the program and data together constitute a hidden achieved.
1.4 hidden concrete realization
Reason for the existence of the access control 1 so that the client programmer can not touch the part (implementation of) they should not reach 2 to allow the library designer to change the internal class work without affecting the client programmer
1.6 Inheritance
It is-a (a) the relationship: can completely replace a group derived class object with a class object, which may be considered as purely an alternative embodiment of the circular geometry.
is-like-a (like a): In the derived class to add a new interface elements, so it extends the interfaces Example: scientific calculators like a simple timer,
