C++ Basic Syntax. Wojciech Frohmberg / OOP Laboratory. Poznan University of Technology. Fields and methods

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1 and methods 1 1 Department of Computer Science Poznan University of Technology / OOP Laboratory

2 and methods Outline 1 and methods Accessibility modifiers Class fields

3 Outline and methods 1 and methods Accessibility modifiers Class fields

4 and methods Inner-class accessibility modifiers syntax Header file 1 //... 2 class ClassName { 3 public: 4 //... public class/object members (default for structs) 5 protected: 6 //... members available only in methods of the class and classes inherited from the class 7 private: 8 //... members available only in methods of the class (default for classes) 9 }; 10 //...

5 and methods Inheritance accesibility modifiers Header file 1 //... 2 #include "parent_class.h" 3 4 class OffspringClass: private ParentClass { 5 // restrict public and protected non-static class members inherited from ParentClass 6 // they will be available only to the OffspringClass members 7 8 class OffspringClass: protected ParentClass { 9 // restrict public parent class members 10 // they will be available only to the OffspringClass members and classes that inherit 11 // from the OffspringClass class OffspringClass: public ParentClass { 14 // do not change parent class members accessibility specifiers

6 Outline and methods 1 and methods Accessibility modifiers Class fields

7 and methods Declaration of non-static class fields syntax Header file 1 //... 2 class ClassName { 3 // <access-modifier> e.g.: public: 4 //... 5 type fieldname[,...]; // one cannot assign default value here! 6 //... 7 }; 8 //...

8 and methods Usage of non-static class fields Code file 1 // In the (sub)class methods in case of protected 2 // and class methods in case of private 3 [this->][classspecyfier::]fieldname = value; 4 // In the other methods/functions iff field is public 5 object.[classspecyfier::]fieldname = value; 6 // or 7 pointer->[classspecyfier::]fieldname = value;

9 Tasks and methods Complete the tasks 1 Create class MyClass with public fields myint and mystring (of type char *). Create instance of the class in the main function and assign value to its fields 11 and "Hello field respectively. Print the values on the standard output. 2 Create class MyOffspringClass that inherits from MyClass. Make sure MyClass contains field myint and mystring like in previous task. In MyOffspringClass also declare field myint and mystring field. Create instance of the MyOffspringClass in the main program function. Assign different values to myint from MyClass and MyOffspringClass fields then print them both on the standard output.

10 and methods Declaration of static class fields syntax Header file 1 //... 2 class ClassName { 3 // <access-modifier> e.g. public: 4 //... 5 static type staticfieldname[,...]; // one cannot assign default value here neighter! 6 //... 7 }; 8 //... Code file 1 // libraries header files... 2 #include "class_name.h" 3 4 // type ClassName::fieldName [ = value [,...]];

11 and methods Usage of static class fields Code file 1 // In a class methods 2 [this->][classspecyfier::]fieldname = value; 3 // however this-> is not necessary as well as ClassSpecyfier:: if the field hasn t been declared 4 // in parent class 5 6 // In other methods functions 7 ClassSpecyfier::fieldName = value; 8 // ClassSpecyfier:: is obligatory here!

12 Tasks and methods Complete the tasks 1 Create class called MyClass and create static field instancescount of type int and initialize it with 0. In main function of the program create three instances of the class and every time increment instance counter. Print instance counter.

13 Outline and methods 1 and methods Accessibility modifiers Class fields

14 and methods Declaration of non-static methods syntax Header file 1 //... 2 class ClassName { 3 // <access-modifier> 4 //... 5 resulttype methodname([paramtype paramname[=defaultvalue,...]]); 6 // non-virtual mothod -- method that cannot be overridden in subclass 7 8 virtual resulttype methodname([paramtype paramname[=defaultvalue,...]]); 9 // virtual method -- method with so called dynamic (late) binding virtual resulttype methodname([paramtype paramname[=defaultvalue,...]]) = 0; 12 // abstract method -- method won t have its implementation in the class // }; 16 //... Code file 1 //... 2 #include "class_name.h" 3 //... 4 resulttype ClassName::methodName([paramtype paramname[=defaultvalue,...]]) { 5 // make sure that the parameter list is the same as in the header file! 6 } 7 //...

15 and methods Non-static methods usage Code file 1 // In the (sub)class methods in case of protected 2 // and class methods in case of private 3 [this->][classspecyfier::]methodsname([parametervalue[,...]]); 4 // In the other methods/functions iff field is public 5 object.[classspecyfier::]methodsname([parametervalue[,...]]); 6 // or 7 pointer->[classspecyfier::]methodsname([parametervalue[,...]]);

16 Tasks and methods Complete the tasks 1 Create class TennisPlayer with a method returnball and field name. Player can succesfully return the ball or fail in returning. To model uncertainty use stdlib.h library (and time.h to produce seed). Create two objects of TennisPlayer class with given names. Until one of the players fail to return a ball print the name of the player and word returned. 2 Expand logic of the above program of the StrikePower (class). Each player should be able to modify StrikePower in each strike only of a few units. The higher the StrikePower, the more difficult the ball should be by the opponent. 3 Create class MyBaseClass with protected field myint. Create class MyChildClass inheriting from MyBaseClass but also with its own field myint. Create global variable myint. Create method myintusage in MyChildClass that has one parameter called myint. In the method body use each one of the myint variable assigning unique value to it and then printing it on the standard output.

17 Overriding method and methods Discussion Overriding method can be reduced to declare once again virtual method with name the same as in parent class followed by binding the implementation in code file.

18 Tasks and methods Complete the tasks 1 Create class Shape with an abstract method getfield. Create class Rectangle that inherits from Shape implementing method getfield. Add two protected fields side1 and side2 and make properties from them (make sure setter methods are virtual). Create class Square inheriting from Rectangle that overrides the setter methods of side1 and side2. Create class Circle inheriting from Shape and similarly implementing getfield method. Circle should contain field radius with its setter.

C++ Basic Syntax. Constructors and destructors. Wojciech Frohmberg / OOP Laboratory. Poznan University of Technology

C++ Basic Syntax. Constructors and destructors. Wojciech Frohmberg / OOP Laboratory. Poznan University of Technology Constructors and destructors 1 1 Department of Computer Science Poznan University of Technology 2012.10.07 / OOP Laboratory Outline 1 2 3 4 5 Outline 1 2 3 4 5 Outline 1 2 3 4 5 Outline 1 2 3 4 5 Outline