This chapter mainly introduces the concept, making the bed for future chapters ~!
1. Class: A class should represent a common abstraction, which is a common attribute of all individual objects of this class;
2. There are two properties of classes: state space and behavior
3. Status Space: The status space of a class C refers to all sets of the allowed state of any object belonging to class C, and the size of a state space is equivalent to a specified state of a given object.
4. Subclass status space: If b is a subclass of A, the status space of B must be completely included in the status space of A. From the perspective of the technology, the state space of B is transmitted to a state of the state. The space refers to the status space that must be located in A. We said that the status space of B is limited to the status space of A.
If b is a subclass of A, then b status space must contain at least a dimension of the status space, or contain more dimensions. If B's status space contains more dimensions, then B The state space is diffused from the state space from A.
5. Behavior of subclasses: Allow behavior of a class C refers to such a set of conversions, ie, an object that allows class C to change the state within the status spatial range of C.
6. Space constraints: Unregisions of classes, a class of invariance refers to a state, that is, every object of this class meets the conditions (when this object is in a balanced state), such as a triangle The class contains three sides of A, B, C, the invariance is A B> = C; A C> = B; B C> = A, (here you allow triangle is a straight line)
7. Pre-condition: The conditions must be met before the operation operation begins to perform;
Back conditions: This condition must be correct at the end of the operation operation.
