Passing Values Between Classes

yes putting input in the constructor or parsing input using properties or functions after the object have been created is what i mostly do

not of cause that mean there could be no better way

Those are the only 3 ways :p

If you're object *needs* the data to work, it really should go in the constructor. After that it's up to you how ya do it.

Thats what I thought, I suddenly remembered from C++ thats how you do it and it kicked me in the head, lol. Easy enough, all I can say is... duh! Thanks :wave:

I believe i am having the same problem, im very new to programming and trying to figure out how to pass variables between classes, i thought keyword 'public' would enable that?


public class class1
{
public string x = "hello";
System.Console.WriteLine ("Hello World!");
}

class class2
{
static void Main()
{
System.Console.WriteLine(class1.x);
class1; //trying to execute class1 from within class2 to write "hello world"
}
}

You have several issues. For one this Class1 won't compile because you can't execute a statement within the body of the class. In order for your Console.WriteLine statement to work you need to put it within a method. Rather than declaring a public field you may want to use a property. Within the Main() method, you need to new up an instance of Class1 before you can use it. Here's the fixed up code.


namespace CGTestConsole
{
#region Using Directives

using System;

#endregion Using Directives

class Class1
{
#region Public Properties

public string Text { get { return _text; } }

#endregion Public Properties

#region Public Methods

public void DisplayText( )
{
Console.WriteLine( _text + " using the DisplayText method." );
}

#endregion Public Methods

#region Private Fields

private string _text = "Hello World";

#endregion Private Fields
}

class Program
{
static void Main( string[ ] args )
{
// Declare an instance of class1
Class1 class1 = new Class1( );

// Write to the console using the get property of class1
Console.WriteLine( class1.Text );

// Write to the console using the class method
class1.DisplayText( );
}
}
}

You can pass a variable to another class by using the "get {} set {}" method and calling it from the class you need it in.

public partial class Main : Form
{
MyClass My_Class = new MyClass();

string myString;

public void makeString()
{
myString = "Hello!";
My_Class.retrieveString();
}

public String Main_String
{
get { return myString; }
set {myString = value; }
}
}

class MyClass
{
Main getString = new Main();

public void retrieveString()
{
string MainString = getString.Main_String;
}
}

Kind of a useless example but I hope it made a point, lol

You can pass a variable to another class by using the "get {} set {}" method and calling it from the class you need it in.

public partial class Main : Form
{
MyClass My_Class = new MyClass();

string myString;

public void makeString()
{
myString = "Hello!";
My_Class.retrieveString();
}

public String Main_String
{
get { return myString; }
set {myString = value; }
}
}

class MyClass
{
Main getString = new Main();

public void retrieveString()
{
string MainString = getString.Main_String;
}
}

Kind of a useless example but I hope it made a point, lol

That wouldn't work at all. "MyClass" creates a "Main" object that has nothing to do with the "Main" object that you're working from.

If you wanted to do it like that you'd have to transfer the "Main" object through MyClass' constructor as a parameter.
But I wouldn't suggest doing things like that at all, if it could be avoided. It makes it a lot harder to maintain. The less classes contain instances of eachother, the better.

I actually used get {} set {} on a new object of my GateMaster class and grabbed a COMPort value from another class and it worked just fine. Though... I will try your method however, it sounds more reasonable than creating a "new" class object when one is already in existence.

The only thing is, when the class your passing goes out of scope, wont the automatic destructor (A.K.A. Garbage Collector) clean it up?

Or does the fact that it inherits from "Form" keep the GC from destroying it because Form is always there so long as the program is running?

Erh, my reply was mainly to your example which wouldn't work (though it would appear to work, because the string you were getting was static). View example below.

And the garbage collector won't destroy it as long as there's something pointing to it somewhere in the program.

Example:

public partial class Main : Form
{
private TextBox t1; // First textbox, will extract text from here
private TextBox t2; // Second textbox, will place whatever's gotten from MyClass her
private Button b1; // Click will start simulation

public Main()
{
InitializeComponent();

// Usually done by designer in VS2005
t1 = new TextBox();
t1.Location = new Point(10, 10);
t2 = new TextBox();
t2.Location = new Point(10, 35);
b1 = new Button();
b1.Location = new Point(10, 60);
b1.Text = "Simulate";
b1.Click += new EventHandler(b1_Click);
Controls.Add(t1);
Controls.Add(t2);
Controls.Add(b1);
}

void b1_Click(object sender, EventArgs e)
{
MyClass myClass = new MyClass();
t2.Text = myClass.retrieveString();
}

public string Main_String
{
get { return t1.Text; }
set { t1.Text = value; }
}
}

public class MyClass
{
Main getString = new Main();

public string retrieveString()
{
return getString.Main_String;
}
}

Another thing in your code you should be careful about is that in your "Main" you create a new instance of MyClass, which creates a new instance of Main, which creates a new instance of MyClass, until you get a stack overflow.

And to add another to the list:
3) Never post code without running it under the debugger. Try out your code first before posting it.

I named it getString because thats kinda what it does in theory, it "gets" the string from the Main class. But this code is kind of obsolete now, lol. I used code similar to it in my TCP/IP chat project but Ive since revised it considerably by using programmer defined constructors and the like.

It was just a simple example and I couldn't think of anything to name my variables in this one so I just tried to make them as generic as possible. Though I guess my naming conventions are STILL evolving. But I have a question. Is Hungarian notation a good idea? I can take it or leave it, but I want to know if its good practice to use it or not? Ive heard arguments from both sides...

I can see the benefits in it, what with being able to tell what the datatype is just by looking at the first 3 or 4 letters, but I can see the downside as well in that it can be kind of confusing in that when you get into different classes and the like, such as SerialPort and NetworkStream, that it might be a bother and its just easier to name them something like "TCPNetStream" or something like that.

EDIT: I usually make up "quick" names for variables while in development because I don't want to spend a lot of time trying to think up descriptive names for variables. That and I'm more worried about just getting the program to work. Later on when everything is humming along Ill take the time and go in and change the names. VS helps a TON with this seeing as how when you change the name of a variable at the declaration it often times changes it throughout the entire assembly which is awesome and makes things go much faster. Though I really should do it while writing the initial code, but then I often end up changing the stuff later on when I decide that something else might work better, I think of a better name, I change some code somewhere and the name is no longer descriptive, etc... Ive only been programming for about a month in "the real world" so I still have a lot to learn about coding etiquette, I'm sure. But these things come with time and experience :)

I named it getString because thats kinda what it does in theory, it "gets" the string from the Main class.
Please reread basic books you have some big misunderstoods here. No it doesn't get a string it is the placeholder for an object so it should have a name which makes understandable that this is an object.
Also Main is a wrong name because this isn't what Main suggests to be
Maybe for your 'Main' class a better name would have been TestFormClass or something like that.


It was just a simple example and I couldn't think of anything to name my variables in this one so I just tried to make them as generic as possible.
Please also clear up what 'generic' means. I couldn't find anything 'generic' in this example.
But I have a question. Is Hungarian notation a good idea? I can take it or leave it, but I want to know if its good practice to use it or not? Ive heard arguments from both sides...
It is as you just say. Arguments for both sides.
In some cases I'm personally using it e.g I name TextBoxes with txt in the firstplce followed by the need of the Box e.g. txtFamilyName or btClose for a closing button. But I dont name all Fields which are integers beginning with an 'i' because the compiler is good enough to check that you are just rying to add an integer to a string or other errors which occur. But this is a bit of private customs and as I have seen granted from other programmers with respect. But giving significant names could be done wrong in different ways. Basically: A Field holds something ( a value, a date, an object ) but it is never doing something . Because of this names using get, let , set ... as prefixes for Fields are not a good idea. Get it.

Animal dog = new Animal(); // good
Animal findACat = new Animal() // very bad

Get the idea of an object. A class is an object. In the above example dog is the place where an object Animal() will be created. It is the adress where you may adress it. And because you have the adress of your Animal class now you can get your Object doing something like

dog.FindBone();
dog.Shout("wauuuu ");

The other error to give significantnames is to overdo it like

string stringMyBigListViewsFirstColumnsHeaderTitleString = "Name"
:lol: You are loughing now. ? I have seen such things already
:lol:

Try to do descriptive names as best as you can, especially for classes but also for variables ( Fileds) because after I while you havn't read your code you would never again find out why in the world you have had
if( d != null && d.Name == stxt ){
for(int l= 0; l < el; l++){
for (int c = 0 c < cm;c++){
...

}
}
}
Do you know whats going on here ? Noooo If you create it you will know whats going on, but half a year later ?
If instead of this you may have

If( document != null && document.Name == docName ){
for (int line = 0; line < endline; line++){
for ( int col = 0; col < colMax; col++){
........
}
}
}

Simple get the idea any you will know how to do.

But these things come with time and experience :) I agree.

ar
tt
al
tnI was thinking these were states. Here's what I have so far:

AR - Arkansas
TT - Um?
AL - Alabama
TN - Tennessee

I was thinking these were states. Here's what I have so far:

AR - Arkansas
TT - Um?
AL - Alabama
TN - Tennessee:D :D :lol: :lol: :lol: :thumb: lol-rofl --