that focuses on building models of

Transcription

1

2 A software design paradigm ("para-dime") that focuses on building models of to solve a programming problem (instead of focusing on )

3 A framework containing the basic assumptions, ways of thinking, and methodology that are commonly accepted by members of a scientific community.

4 An Object is composed of: and

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

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

7 is a of an Object, including: define what outside/communicating classes may directly access.

8 A is to an as a is to a as a is to a

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10 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

11 class { public: private: };

12 is the same as a variable declaration class { public: string firstname="", lastname=""; private: int age=0; float shoesize=0; };

13 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); };

14 in a file called class fraction { public: void set(int n, int d); void setnumer(int n); void setdenom(int d); int getnumer(); int getdenom(); float getdecimal(); private: int numer=0, denom=1; void reduce(); };

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

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

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

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

19 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; }

20 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; }

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

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

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24 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 }

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26 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"

27 // and are values that the "outside" wants to set numer //and denom to...should we let them?? void fraction::setnumer(int n) { numer = n; } void fraction::setdenom(int d) { } if (d <= 0) // denom should be > 0 else cout << "Nope!!\n"; denom = d;

28 // the outside world wants to know the value of // a private Data Member. We will give them a COPY // if the class has a data member: int fraction::getnumer() { return numer; } int fraction::getdenom() { return denom; } //note: return type same as Data Member's type

29 const int MAX = 20; // outside of class, in header class pricelist { public: void setprices(double p[], int nump); int getprices(double p[]); // returns numprices private: double price[max]; int numprices = 0; // init as "empty" };

30 void pricelist::setprices(double p[], int nump) { // standard error check: num in range if (nump < 0 nump > MAX) return; // exit now! for (int i=0; i< ; i++) // use given num = p[i]; // copy arg to data mem = nump; // copy arg to data mem }

31 int pricelist::getprices(double p[]) { // arrays always PBR // copy data members to argument and return val for (int i=0; i< ; i++) // use data member p[i] = ; // copy data mem to arg return ; // return data mem }

32 void main() { pricelist x; // allocates a pricelist object double d[3] = {1.5, 2.9, 0}; // plain old array int num = 2; // 2 items in use x.setprices(d,num); // copy list into object num = x.get(d); // copy list out of object }

33 Initialization of data members of an object at the time it is allocated (declared). Initial values are specified in the class interface with the data member declarations.

34 class fraction { public: int numer ; int denom ; }; void main() { fraction a; // a.numer=0, a.denom=1 NOW! fraction b[3]; // all 3 numers set to 0 NOW! // all 3 denoms set to 1 NOW!

35 Term Class Object Public Private Paradigm Members Methods Interface Implementation Construction 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. Initializing (assigning a value) to members of an object at the time the object is allocated/declared. A function that is not part of a class.