Recap, Test 1 prep, Composition and Inheritance

Dates Test 1 – 12 th of March Assignment 1 – 20 th 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 Design  At least ONE c++ GUI referenced  Design pattern(s) mentioned  UML diagram of your proposed system  Paragraph on event programming (ideally reference sources)

Assignment 1 requirements GUI Design  At least ONE cue game referenced (game and possibly real life)  Diagram of interface placement  Brief 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_GUARD class myclass { … }; #endif

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

#define Define constant functions #define MIN(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 = ;

Common errors Compiler errors Linker errors Execution error Logical error

Compiler errors Typographical errors  > instead of >>  Forgetting ; Other errors  Not declaring a variable  Not defining a function before main  Trying to access private variables  Including the wrong header file  Mismatched 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

library / / 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 values  Requires dereferencing to assign values

Pointers

1729 Address Value NULL Computer c = new Computer(); int x =1729; int* z = &x;

Arrays 0x C1 (0) 0x D7 (1) 0x E2 (2) 0x F9 (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 array for(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 inherit  Constructors  Destructors  Copy constructors  Friends

Instantiation of a subclass