[unity entry program] C ＃ and unity - understand classes and objects

Catalog

1 The concept of object-oriented programming

2 C# Three characteristics of object-oriented

2.1 encapsulation

Access modifier

2.2 Inherit

2.3 polymorphic

3 object

4 class

Static member of class

5 class &Unity Components

5.1 Class in Unity Use

5.2 Visualization of class objects in the attribute window

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Because of study C# Is for Unity To prepare for , Therefore, only simple learning records are made for classes and objects .

1 The concept of object-oriented programming

As long as you touch C# I must have heard this sentence “C# Is an object-oriented programming language ”, So what is object-oriented programming ？

object-oriented programming ——OOP（Object-Oriented Programming）, It refers to describing everything as an object in programming , Because of this , Object oriented programming is more readable , It is also easier to understand , That's why I say with C++ comparison C# It will be easier to learn .

2 C# Three characteristics of object-oriented

2.1 encapsulation

encapsulation , That is, one or more projects are enclosed in a package , Hide the details of the internal state and function of the object , Provide some public elements for access . Let's take the mobile phone as an example ： Some operations can be carried out through some keys of the mobile phone , But we don't know how the internal hardware of the mobile phone realizes these operations . Encapsulation allows users not to care about how objects are implemented , Just know the usage of the object .

abstract And encapsulation are often mentioned together , After realizing encapsulation , Some abstract public elements provided —— class 、 Methods to realize the visualization of information , However, the access rights of users to these information are not all public .

Access modifier

C# Package utilization Access modifier To set user access rights ,C# There are the following access modifiers （ If there is no limit , The default is private）

• public—— public , Members of a class can be accessed from outside the class
• private—— Can only be accessed within a class
• protected—— Only this kind of object and its children can access
• internal—— Objects in the same assembly can access
• prtected internal—— This category 、 Derived classes or assemblies containing them are accessible  

2.2 Inherit

C# The inheritance of is mainly reflected in the inheritance between classes , Through inheritance, we can define another class according to one class , Improve code reuse . For example, in the following code

public class MyPlayer : MonoBehaviour
{
    ...
}

Created a new class MyPlayer, It inherited Unity Script API Basic classes in MonoBehaviour, That means inheriting the data members and member functions of this basic class , There is no need to write repeatedly .

In this relationship ,MyPlayer be called Derived class ,MonoBehaviour be called Base class .

2.3 polymorphic

The same behavior has different representation forms , Or implement inherited properties or methods in different ways , This is called polymorphism . stay C# Polymorphism is embodied by class inheritance or interface .

3 object

Briefly understand what is an object ： Objects include properties and methods

• attribute —— Inherent properties of objects
• Method —— Behavior methods of objects

Suppose we have a mobile phone object , Then the style of mobile phone 、 The model is its attribute , And make phone calls with mobile phones 、 Texting and other operations are its methods .

4 class

C# Everything in is related to classes and objects and their properties and methods , When you define a class , It defines a blueprint for data types . for instance ： A student is a “ class ”, And a student named Xiao Ming , He became a “ object ” 了 , Class is more like a concept , The object is the class Instantiation Become an individual with specific information .

Static member of class

Class members are divided into instance members and static members .

Static members —— have access to static Keyword modifies class members to static .

When a member is declared static , No matter how many class members are created , They will only have a copy of the static member .  Static variables are used to define constants in classes , Without creating an instance, you can directly call the class to get , It can be defined externally or internally .

5 class &Unity Components

When using static methods or properties of classes , There is no need to instantiate the class , In addition, all C# Classes in must be instantiated into objects before they can be used .

5.1 Class in Unity Use

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using System;

public class MyPlayer : MonoBehaviour
{
    public string myName;
    public Cat cat;
    void Start()
    {
        cat.Print();
    }
}

[Serializable]
public class Cat
{
    // Data member 
    public string name;
    public int age;

    /*// Constructors 
    public Cat(string name, int age)
    {
        this.name = name;
        this.age = age;
    }*/

    // Member method 
    public void Print()
    {
        Debug.Log($" The kitten's name is {name}, It's this year {age} Year old ");
    }
}

  Input name and age after ,ctrl+p Results of operation

5.2 Visualization of class objects in the attribute window

stay Unity in , We all know that if you want to visualize a defined variable , add public that will do , for example

  

But to visualize the class objects defined in the script , Add only public It's not enough. , You also need to add

[Seralizable] It's in the namespace System Under the

such , The object created by this class plus public You can visualize it in the attribute window .