[내일 배움 캠프 Unity 4기] 04.23 TIL

Goals

• Study the C#;
  • Condition and Loop
  • Array and Collections
  • Method and Structure
  • Class and Object

---

C# study

if

When script are running, the command that we want to be execute with the condition can be written with the if statement.

bool condition1 = true;
bool condition2 = false;
if(condition1 && condition2)
{
	// commands what you want to execute if `condition` is true;
    Console.WriteLine("This is true and true");
}
else if (condition1 || condition2)
{
	Console.WriteLine("This is true or false");
}
else
{
	Console.WriteLine("This is false and false");
}

switch

Similar with the if, the switch consist of the case and default

int cond = 2;
switch (cond)
{
	case 0:
    	Console.WriteLine("0");
        break;
    case 1:
    	Console.WriteLine("1");
        break;
    case 2:
    	Console.WriteLine("2");
        break;
    default:
    	Console.WriteLine("the number is not in the range of 0 ~ 2");
        break;
}

---

for & while

When we want to repeat the command, the for and while can be used for the command loop
For the for, it needs 3 argument with the separating ; like below example.
for(int i=0; i<10; i++)
the first argument is the declaration of variable which changes with the loop.
the second argument is the condition for the loop. the loop will be execute when the condition is true
the third argument is the changes. when the commands run inside the loop, the variable would changes according this argument
This is an example for using for

for(int a=0; a<9; a++)
{
	Console.WriteLine(a);
}

Similar with the for, the while can be used to repeat the command. the differences are the number of arguments. Since the for needs 3 arguments, it can be facilitate to the independently. The while, However, needs only condition. With this feature, the while is adopted the number of loop assosiated outside of loop command. See the example

bool extCond = false;
while(extCond)
{
	Console.WriteLine("extCond is true");
}

Main difference of for and while is the area of variable. When we used loop for fixed number or independently, the for loop seems to be clear. In the case of the loop which related to the variable of outside, the while loop is more appropirate to write clearly.

---

Array and Collections

To create the group of variable which contains same types of data, the Array can be one of the choice. Usage of the array can be seen at the below example

// declaration of array
int[] arr_int;

// initialization
arr_int = new int[3];

// decl + init
int[] arr_int2 = new int[4];

... /// fill the elements

// call the element of array
Console.WriteLine(arr_int[0]);
Console.WriteLine(arr_int2[0] + arr_int2[1]);

Typically, the array were used with the for loop to access the element with loop index.

List

Similar with the vector on C++, it is kind of array whose size is not fixed. To use this container, we should write the type of variable inside of bra-ket<>. After attaching the indicator of list and declaration sentence, we created List variable

// create new list variable
List<int> listName = new List<int>();

// insert the valus to the list
listName.Add(0); 
listName.Add(1); 
listName.Add(2); 
listName.Add(3); 
listName.Remove(3);

// access each element
foreach(int i in listName)
{
	Console.WriteLine(i);
}

	vector	List
Environment	C++	C#

Dictionary

Similar with the map on C++, the key-value pair were stored in this variable

// create new dictionary
Dictionary<string,int> dic_var = new Dictionary<string,int>();

// insert the key-value pair
dic_var.Add("Test",0);

// access the element
foreach(KeyValuePair<string,int> pair in dic_var)
{
	Console.WriteLine(pair.Key+" " + pair.Value);
}

	map	Dictionary
Environment	C++	C#

HashSet

Similar with the set on C++, the group of variable without overlap can be defined on C#.

// create new hashset
HashSet<int> set_int = new HashSet<int>();

// insert the value on set
set_int.Add(1);
set_int.Add(1);
set_int.Add(2);

// call the element of set
foreach(int ele in set_int)
{
	Console.WriteLine(ele);
}

	set	HashSet
Environment	C++	C#

---

Method

The group of codes, facilitated for the re-use of code snippet

[access] [return type] [name] ([argument])
{
	// commands that you want to execute
}

For example, we can write like below

// define the method(so called as function) 
public int AddNumber(int a, int b)
{
	int result = a+b;
    return result;
}

// overloading
public int AddNumber(int a, int b, int c)
{
	int result = a+b+c;
    return result;
}

void Main(string[] args)
{
	int a=10;
    int b= 4;
    int c = AddNumber(a,b); // call the method
    Console.WriteLine(c);
}

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Class

Object-Oriented Programming(OOP) has advantage written on the bottom

1. Encapsulation
   • This property gives us good stability and maintanance by limitating the access authority
2. Inheritance
   • Building the hierachy on the class will reduce the task to write same command. also this feature serve the reusabilty of code on parent class
3. Polymorphism
   • Improve the readability of code and facilitate the code with flexibility
4. Abstraction
   • Simplify the property and focus the role of code
5. Object
   • Classifying the method and data of the class, modularization was done

---

Structure

Ref Link

Q & A

Difference between 'if' and 'switch'

pros and cons

if:
1. processing the condition sequantially
2. writing if, if else and else shows different length -> worse readability
3. the total processing time is proprtional to the number of conditions
4. advantage comes from the memory usage.

switch:
1. jump the processing line directly
2. each case looks like similar length -> good readability
3. fast processing time because unnecessary commands were skipped
4. whole case were allocated to the memory. the more case written, the less available memory

How can we make >2 dimensional array?

A.

int [,] arr_2d = new int[4,3]; // create 4x3 array

... // fill the elements

Console.WriteLine(arr_2d[0,1]); // call the element at 0,1 index

int [,,] arr_3d = new int[4,3,5]; // create 4x3x5 array

... // fill the elements

Console.WriteLine(arr_3d[0,1,2]); // call the element at 0,1,2 index

Structure vs. Class

Structure: value type, used for simple type of data
Class: With the inheritance, the class is used to construct complex data structure