7 replies to this topic

[bhw13]

Hi All,

 

I am new to the Netduino and new to C# programming. I have been reading the very well written Chris Walker Getting Started book, but I would like clarification on how the following code line is constructed:

OutputPort led = new OutputPort(Pins.ONBOARD_LED, false);

Is OutputPort a class and led an instance of the class? Are the items in the parentheses parameters? Is this code line creating the instance variable led or is some different process going on here? Maybe i haven't read far enough in my C# programming books.

Thanks very much

[Chris Walker]

Hi bhw13, OutputPort is a class (Microsoft.SPOT.Hardware.OutputPort) which lets you set the voltage of a pin to 3.3V or 0V (GND). Pins.ONBOARD_LED returns a Cpu.Pin value which tells OutputPort which microcontroller pin to use. "led" is the instance of OutputPort, in this example, which now controls the onboard LED. [The onboard LED is connected to a microcontroller pin--which why it's "Pin" value.] Welcome to the Netduino community, Chris

[bhw13]

Thanks, Chris for the quick response. I also received gracious responses from others in the chat room today who pointed me in the direction of the concept of a constructor to explain the parameters inside the parentheses of OutputPort. I have a few C# books, but the presentation and explanation of this doesn't seem straightforward. If anyone can shed some further light on this (I'm aware this is not really a C# teaching forum), I'd appreciate it- I'm trying to understand a little better the structure of the C# language applied in this case.

[hanzibal]

Why not write some class of your own and step through the code to see what happens as parameters are passed to the constructor.

 

The constructor is a method that is called to instanciate a class, i.e. create a live object from a class definition.

 

For example you could try this:

 

[font="'courier new', courier, monospace;"]class Person[/font]

[font="'courier new', courier, monospace;"]{[/font]

[font="'courier new', courier, monospace;"] string _name;[/font]

[font="'courier new', courier, monospace;"] int _age;[/font]

 

// this is the class constructor

[font="'courier new', courier, monospace;"] public Person(string name, int age)[/font]

[font="'courier new', courier, monospace;"] {[/font]

[font="'courier new', courier, monospace;"]  // this will make the object "remember" the paramters[/font]

[font="'courier new', courier, monospace;"] _name = name;[/font]

[font="'courier new', courier, monospace;"] _age = age;[/font]

[font="'courier new', courier, monospace;"] }[/font]

 

[font="'courier new', courier, monospace;"] public void SayHello()[/font]

[font="'courier new', courier, monospace;"] {[/font]

[font="'courier new', courier, monospace;"]   System.Diagnostics.Print("Hi, my names is" + name + " and I'm " + age.ToString() + " years of age.");[/font]

[font="'courier new', courier, monospace;"]  }[/font]

[font="'courier new', courier, monospace;"]}[/font]

 

You would then create an instance of the class like so:

 

[font="'courier new', courier, monospace;"]var peter = new Person("Peter", 25);[/font]

 

The object "peter" will remember it's name and age and persist these throughout the object's lifetime (e.g. until you delete the object). Run the code and pay attention to what gets printed in the debug window when you add a call to the SayHello(.) method:

 

[font="'courier new', courier, monospace;"]peter.SayHello();[/font]

 

Hope this help you in understanding the concept of passing parameters to a class constructor.

[JerseyTechGuy]

Hi All,

 

I am new to the Netduino and new to C# programming. I have been reading the very well written Chris Walker Getting Started book, but I would like clarification on how the following code line is constructed:

OutputPort led = new OutputPort(Pins.ONBOARD_LED, false);

Is OutputPort a class and led an instance of the class? Are the items in the parentheses parameters? Is this code line creating the instance variable led or is some different process going on here? Maybe i haven't read far enough in my C# programming books.

Thanks very much

 

Hi bhw13 and welcome to the community.  You may want to check out something like 30 Days to Learn C# from Tuts+. They offer good courses and a good pace.  You take a section a day and each section is between 10 minutes and 30 minutes.

 

Happy Programming.

[dustmouse]

Hi All,

 

I am new to the Netduino and new to C# programming. I have been reading the very well written Chris Walker Getting Started book, but I would like clarification on how the following code line is constructed:

OutputPort led = new OutputPort(Pins.ONBOARD_LED, false);

Is OutputPort a class and led an instance of the class? Are the items in the parentheses parameters? Is this code line creating the instance variable led or is some different process going on here? Maybe i haven't read far enough in my C# programming books.

Thanks very much

 

It sounds to me like you have the concepts down.  I would suggest picking up an intro to C# book (or another language - but obviously C# makes more sense for Netduino development), unless you are mostly interested in the hardware side of things.

[bhw13]

Ok, thank-you all again for your helpful suggestions. I found a short youtube video that talked about constructors.

I came up with the following piece of code. The constructor is created by public Program(). The second line of code that I'm showing here seems to have the same form as the line of code

in my original question. The 5 and 10 are obviously int's, but I imagine that you can use variables for the parameters. Sorry, again, for all this simple stuff.

 

static void Main(string[] args)

{ Program pr = new Program (5,10);

  Console.Read();  }

public Program( int s, int t)

{  Console.WtiteLine(s);

Console.WriteLine(t);  }

[hanzibal]

Yes, you can pass varibles to a constuctor, e.g. like so:

 

static void Main(string[] args){   int a = 5;   int b = 10;   Program pr = new Program (a, b );   Console.Read();}