Recap, Test 1 prep, Composition and Inheritance

Dates

Test 1 – 12th of March Assignment 1 – 20th of March

Test 1 contents

Syntax checking Error identification Code correction Problem solving Code identification Pass by value and Pass by reference Const Pointers will not be tested

Assignment 1 requirements

GUI Software DesignAt least ONE c++ GUI referencedDesign pattern(s) mentionedUML diagram of your proposed systemParagraph on event programming (ideally

reference sources)

Assignment 1 requirements

GUI DesignAt least ONE cue game referenced (game

and possibly real life)Diagram of interface placementBrief discussion

User interface controls

Classes Private default scope Automatically implements a default

constructor and copy constructor Uses a destructor Instantiated using myclass a; or myclass

b(); Header file contains the definitions .cpp (Source) file has the declarations

Classes

Inline functions are declared in the header file A class definition is always ended with a

semicolon ; If an overloaded constructor is implemented the

default will not be available unless explicitly defined and declared

Every member function has access to the THIS pointer this->getVar() or (*this).getVar()

Header example

CPP example

Scope

Local – In a function Global – Outside a function and

class/namespace

Macros

#include #define #ifndef

#ifndef _INCL_GUARD #define _INCL_GUARDclass myclass{…};#endif

System specific code

#ifdef __linux__ //linux code #elif _WIN32 // windows code #elif __ANDROID__ //android code#else

http://sourceforge.net/p/predef/wiki/OperatingSystems/

#define

Define constant functions#define MIN(a,b) (((a)<(b))?(a):(b)) #define MAX(a,b) (((a)>(b))?(a):(b))

#define SWAP(a, b) { a ^= b; b ^= a; a ^= b; } Define constant variables

#define GRAVITY 8.9f#define OOPS SWAP;

Typedef

typedef int i32; typedef long long l64;

e.g. l64 mylong = 123323;

Common errors

Compiler errors Linker errors Execution error Logical error

Compiler errors Typographical errors

> instead of >> Forgetting ;

Other errorsNot declaring a variable Not defining a function before mainTrying to access private variables Including the wrong header fileMismatched braces {Ambiguous function calls

Linker errors

A function with no declaration A library not linked too

Execution errors Out of array bounds Assigning a NULL pointer, a value

Logical errors

while (x=y) Iterating an address of an array out of

bounds

<cmath> <math.h> library

http://www.cplusplus.com/reference/cmath/

trunc, ceil, pow, cos, tan, log

Const void myfunc(const int & val); //passes a

const reference void myfunc(const int val); //passes a

constant value int getGravity() const; //a function with a

const return int const * const myvar; //constant pointer int const * myvar; //variable pointer const char * myvar;

Strings Has a member char* (c-strings are char*) Is a class: string mystr(“words”); Is an array uses mystr[0] notation Uses mystr.push_back(char); + concatenates strings and characters .find(“str”) returns position of str in string .substr(position, length)

Passing by value

Makes a copy of the variable passed into the function

Does not change the original variable

Passing by reference

Passes ONLY the variable we want to change

Does not make a copy

Passing by address

Passes the memory address Treats the variables passed as addresses

not valuesRequires dereferencing to assign values

Pointers

1729

Address Value

NULL

Computer c = new Computer();

int x =1729;int* z = &x;

Arrays

0x6339392C 1 (0)

0x6339392D 7 (1)

0x6339392E 2 (2)

0x6339392F 9 (3)

Array name

Multidimensional arrays

Int twoD[2][3]; twoD[0][2] = 5; twoD[1][1] = 3; int twoD [2][3] = { 1, 7, 2, 9, 2, 1, }; int twoD [2][3] = { {1, 7, 2}, {9, 2, 1} };

int ** twoD = new int*[2];for(int i=0; i < 2; ++i){

twoD[i] = new int[3];}

X size

Y size

2D array using dynamic memory

Clean up

For each array delete[] the arrayfor(int i=0; i < 2; ++i){

delete[] twoD[i];}delete[] twoD;

Arrays can be passed in functions as func(int[] myarr)

However func(int[][] my2darray) is invalid func(int** my2darray) is valid syntax

Various examples of Prac 2 Q1+Q2

Inheritance

Inheritance allows code reuse by enabling the creation of sub-classes based on base classes

Syntax of inheritance:class subclass: access_level baseclass1,access_level

baseclass2{};

Class Dog : public Mammal, public Canine Avoid multiple inheritance

Inheritance

When a sub class is instantiated the base class constructor is called by default

The access level describes the maximum access level that members of the sub class will have

The default access level is private for classes and public for structs

Sub classes

Do not inheritConstructorsDestructorsCopy constructorsFriends

Instantiation of a subclass