Problem with custom constructor for a struct

10/06/2013 18:33 desTenshi#1

Hay guys i have the following problem:

I have a struct for saving some faked "weather" data. So i want to store a random number as measure value and the date + time it was measured. My teacher told me to use a custom constructor so that i can give the values when creating a new one. So far so good but when i did it Visual Studio marked me the first value in the master constructor as error.
The error is :

PHP Code:


			
The this object can only be used when all fields have been assigned.

And this is the struct code :

PHP Code:


			
struct WeatherData
    {
        private int _fakeValue;
        private string _fakeDate;
        // getter und setter for the privat members
        public int FakeValue
        {
            get { return _fakeValue; }
            set { _fakeValue = value; }
        }
        public string FakeDate
        {
            get { return _fakeDate; }
            set { _fakeDate = value; }
        }
        // overrides the inherited ToString method with my own version
        public override string ToString()
        {
            return String.Format("Wert: {0}, gemessen am: {1}", FakeValue, FakeDate);
        }

        public WeatherData(int value)
        :this(value, DateTime.Now.ToString()){}

        public WeatherData(string date)
        :this(0, date){}

        // here is the error but i don't know why... 
        public WeatherData(int value, string date)
        {
            this.FakeValue = value;
            this.FakeDate = date;
        }
    }

So would be nice if anyone could tell me what's wrong there ^^
And if you have any ideas of making it better just tell me :o

desTenshi

ps:

This whole program is a school project i got from my teacher, so don't say something about the topic of it xD ...

10/06/2013 20:42 Easy-Emu#2

You should inside the class:

Code:

public WeatherData(int value, string date)
{
    _fakeValue = value;
    _fakeDate = date;
}

10/06/2013 21:01 desTenshi#3

Quote:
Originally Posted by Easy-Emu
You should inside the class:
Code:
public WeatherData(int value, string date)
{
    _fakeValue = value;
    _fakeDate = date;
}

Well in this case it would be ok if i use it, but if i would use any tests or something in the setter i would have to use this code again here. So in my eyes it's not the best way to solve the problem by just using the private variable :/

10/07/2013 03:18 nkkk#4

another solution is calling the default contructor before wich sets all fields to their default values:

Code:

        public WeatherData(int value, string date)
            :this()
        {
            this.FakeValue = value;
            this.FakeDate = date;
        }

note that you cannot change the compiler generated default constructor. i think this is more a question of taste then of anything else.

10/07/2013 11:20 desTenshi#5

Quote:
Originally Posted by nkkk
another solution is calling the default contructor before wich sets all fields to their default values:
Code:
        public WeatherData(int value, string date)
            :this()
        {
            this.FakeValue = value;
            this.FakeDate = date;
        }
note that you cannot change the compiler generated default constructor. i think this is more a question of taste then of anything else.

Well that works. But i still don't understand why VS say's that's an error.. I can compile it and it works just fine.
I know i cant change the default constructor for a struct, but in which way does this effect the main constructor? (sorry if that's a stupid question :x )

10/07/2013 12:15 Shawak#6

You don't use :this() {..}

Code:

	public WeatherData(int value)
	{
		WeatherData(value, DateTime.Now.ToString());
	}

	public WeatherData(string date)
	{
		WeatherData(0, date);
	}

        public WeatherData(int value, string date)
        {
		_fakeValue = value;
		_fakeDate = date;
        }

Edit: nvm, mixed something up

10/07/2013 14:06 Easy-Emu#7

Quote:

Originally Posted by desTenshi

Well in this case it would be ok if i use it, but if i would use any tests or something in the setter i would have to use this code again here. So in my eyes it's not the best way to solve the problem by just using the private variable :/

it's normal to use private variables inside the class and the public getter/setter only in other classes

10/07/2013 14:21 desTenshi#8

Quote:

Originally Posted by Shawak

You don't use :this() {..}

Code:

	public WeatherData(int value)
	{
		WeatherData(value, DateTime.Now.ToString());
	}

	public WeatherData(string date)
	{
		WeatherData(0, date);
	}

        public WeatherData(int value, string date)
        {
		_fakeValue = value;
		_fakeDate = date;
        }

Why ? It's normal constructor chaining?

Quote:

Originally Posted by Easy-Emu

it's normal to use private variables inside the class and the public getter/setter only in other classes

Well but that would be against the logic to implement the code only once.
Also the book Pro C# 5.0 and the .net 4.5 framework tells to use the c# properties. In my eye's it's smarter than write the code for class / struct data checks two times.