A Paradigm (para-dime) is a framework containing the basic assumptions, ways of thinking, and methodology that are commonly accepted by members of a

Transcription

1

2 A Paradigm (para-dime) is a framework containing the basic assumptions, ways of thinking, and methodology that are commonly accepted by members of a scientific community.

3 So far this semester, we've been concentrating on the POP Paradigm

4 - Start with one procedure (function) that represents the entire program - Identify/specify a few sub-steps of the one procedure - Repeat this refinement process for each procedure until each procedure is simplistic (performs one specific task). Each procedure something, and that is usually reflected in its name as a verb.

5

6 A software design paradigm that focuses on building models of to solve a programming problem (instead of focusing on )

7 1. Identify the "natural" Objects in the project description 2. For each Object, identify its: - Name - Data Elements - Operations to/for/with/on ONE object 3. Design the interaction/communication between objects.

8 An Object is composed of: and

9 May be simple pieces of data (number, character, string, etc.) OR other objects. They are called: - in C++ - in Java

10 perform actions on the data elements and/or communicate with other objects They are called: - in Java - in C++

11 is a of an Object, including: these define what "the outside world" may directly access.

12 A is to an as a is to a as a is to a

13

14 is divided into two parts: declarative information usually written in.h file (called a Header File) - Function Member declarations usually written in a.cpp file

15 class { public: private: };

16 is the same as a variable declaration class customer { public: string firstname, lastname; private: int age; float shoesize; };

17 same as the header line of a function declaration, with a semicolon on the end. class { public: void print(int x) private: int getstuff() float calcstuff(float x, float y) };

18 in a file called class fraction { public: void setnumer(int n); void setdenom(int d); int getnumer(); int getdenom(); float getdecimal(); private: int numer, denom; };

19 Remember from functions that a is a to the compiler that we will write a function, but it is declared elsewhere. The Implementation "fulfills" the promises made in the Interface.

20 For each function member prototyped in the interface: { :: ( ) }

21 in a file called void fraction::set(int n, int d) { } void fraction::getnumer(){ } void fraction::getdenom(){ } float fraction::getdecimal(){ } void fraction::reduce() { }

22 Within all Function Members of a class, all Data Members have (but also can be!)

23 void fraction::set(int n, int d) { numer = n; // data mem = arg denom = d; // data mem = arg } float fraction::getdecimal(){ // localvar = expression w/ data mems float dec = (1.0 * numer)/denom; return dec; }

24 A function that is not a Method of a class. It does not have in front of its name. int largest(int a, int b) { if (a > b) return a; else return b; }

25 After all that work...what have we accomplished?? Essentially, we've invented a new...except it is more complex than a Type, and so we call it a. Now the class name can be used the exact same way as a Type (ex: any way is used).

26 void funstuff() { // allocate 3 of, nothing new double a,b,c; } // allocate 3 of fraction f1, f2, f3;

27

28

29 void funstuff() { fraction f1; f1.numer=1; //error: numer is private f1.denom=0; //error: denom is private f1.set(2,3); float d = f1.getdecimal(); cout << d; // prints }

30 are (special) function members where: - their name is exactly the same as the class name - they do not have a return type - they must always be public - they are automatically invoked whenever an object is allocated (declared). to initialize data members at the time they are created.

31 class fraction { public: fraction(); // constructor prototype private: int numer; int denom; }; fraction::fraction() { // constructor declaration numer = 0; denom = 1; }

32 void main() { fraction f; fraction fr[3]; } // constructor executed NOW! // f.numer = 0, f.denom = 1 // 5 constructors exec. NOW! // fr[0].numer=0, fr[0].denom=1 // fr[1].numer=0, fr[1].denom=1 // fr[2].numer=0, fr[2].denom=1

33 All Data Members should be (unless there is a very good reason to make them public) Code and Function Members for each Data Member to control access from the "outside world"

34 Return a COPY of the data member

35 class fraction { public: getnumer(); // return type is the same private: numer; // as the data member }; int fraction::getnumer() { return numer; }

36 Pass the new value in as an argument Assign the argument to the data member if the argument's value is valid

37 class fraction { public: void setdenom( newden); // argument type private: denom; // same as member type }; void fraction::setdenom(int newden) { if (newden > 0) { // denom should be > 0 denom = newden; } // else print error, do something else, or do nothing }

38 //in a file called class fraction { public: fraction(); void setnumer(int n); void setdenom(int d); int getnumer(); int getdenom(); private: int numer, denom; };

39 //in a file called fraction::fraction() { numer=0; denom=1; } int getnumer() { return numer; } int getdenom() { return denom; } void setnumer(int n){ numer = n; } void setdenom(int d) { if (d > 0) { denom = d; } }

40 Term Class Object Public Private Paradigm Members Methods Interface Implementation Constructor Free Function Definition a description of an object, including a name, list of data members, list of function members (methods), and the access levels of each. allocated instantiation of a Class, containing the members and methods defined in the Class with the designated access levels. designates data members and methods that CAN be directly accessed by the code using the object designates data members and methods that can NOT be directly access by the code using the object. A framework containing the basic assumptions, ways of thinking, and methodology that are commonly accepted by members of a scientific community. Data elements of a class/object. Functions/operations of a class/object. Declarative portion of a class: defines the name, members, list of methods, and their access levels. Coding of the Methods of a class; where the methods are written. Function member with the same name as the class, used to initialize objects of the class. A function that is not part of a class.