C ＃, introductory tutorial -- a little knowledge about function parameter ref and source program

One 、 The story of opening a hotel room

function （Function or Method or ...） It's the main body of the program , Pillar .

A function often used ： Exchange data between two variables .

By default , That's how it's written ：

int a = 10;
int b = 20;

int tmp = a;
a = b;
b = tmp;

If every time I meet , That's what they say , Is it a little trouble ？ That is .

Remember two basic principles ：

（1） As long as it's a repetition , Just write a function ！

（2） As long as it is a relatively long thing （ Code ） It is divided into several functions ！

thus , Of course, you need to write a function to complete this repeated task .

that , Is that what it says ？

...

public static class Globals
{
    public void swap(int a, int b)
    {
        int tmp = a;
        a = b;
        b = tmp;
    }
}

...

int a = 10;
int b = 20;

Globals.swap(a, b);

Of course , As you expected or More than you expected , This code does not implement a,b Data exchange function .

The end result is a = 10;b = 20;！！！！！

analogy ： You and your friends , Changed rooms , But there was no room key exchange ！ I have to go back to my room to sleep at night .

Exchange function swap It should be ：

public static class Globals
{
    public void swap(ref int a,ref int b)
    {
        int tmp = a;
        a = b;
        b = tmp;
    }
}

The difference lies in ref ！！！！！

ref = reference , quote （C/C++ The pointer inside ！）.

usage ：

int a = 10;
int b = 20;

Globals.swap(ref a, ref b);

analogy ： You and your friends , Exchanged room keys , It doesn't matter which room you are in now ！ Go to another room to sleep at night ！

Two 、 Passengers' choice

Knock on the blackboard ！ Key points ： If the parameter is passed in , Modifying data , And new data needs to be sent out （ The back should be sprinkled ！）, Must be used ref.

 

C# There are many types of data , Is it necessary to ref Well ？ No ！

note ：

（1）int,double,float,decimal,char,byte,string wait , If Pass in 、 Efferent , You need to ref.

public void func(ref string a, ref string b)
{
    //  modify  a, b  The data of ;
}

（2） Array 、 list 、 Pile up 、 Stack and other data sets , Unwanted .

array Array

public void func(double[] a, double[] b)
{
    //  modify  a, b  The data of ;
}

 list list

public void func(List<double> a, List<double> b)
{
    //  modify  a, b  The data of ;
}

（2）Complex, Matrix And so on, we or our friends define the extension type and class ,struct , There is no need to ref.

public void func(Complex a, Complex b)
{
    //  modify  a, b  The data of ;
}

A little bit more simple ： As long as it is not a basic data type , commonly （！！） No need ref .

Non-basic data types , Is a combination of data , What is exposed to everyone is the room card .

double[] a; It's the type , It's a room card ！

a[0] Is the data ; Not a room card ！

Let's have a preliminary understanding of .

There is another keyword out , Very very much like ！

I'll give you a special introduction later out.

Oh ！ also in.