C#•16mo ago

❔ initiating Constructor

Why cant I sometimes initiate data members in a constructor like this: Public Car (int wheels, string color) { Wheels = wheels Color = color } And only use this.color = color this.wheels = wheels What is the difference? Why do we have use this at all?

16 Replies

Joreyk ( IXLLEGACYIXL )•16mo ago

if you have color = color then you would set the local color to that which is setting itself with itself because the local variable shadows the instance property if you have this.color = color you say take the local color and set it on the instance property as you explicitly write the location of it how is C# supposed to differentiate between the local variable and the property when they have the same name

McMahoneOP•16mo ago

Edit: why cant we only use default constructor

Joreyk ( IXLLEGACYIXL )•16mo ago

if you dont have a local variable color and only the this.color then you dont have to write this. as C# wont find locally a color so it searches anyway in the instance of the object for color as its not shadowed this has nothing to do with constructors 👀

McMahoneOP•16mo ago

Ahh I see, I only see this in constructors. Thats why I thought it had something to do with constructors

Joreyk ( IXLLEGACYIXL )•16mo ago

public void PaintCar(string color)
{
  color = color;
}

public void PaintCar(string color)
{
  color = color;
}

will have 0 effect in your car example

McMahoneOP•16mo ago

What do you mean locally? Sorry, Im new and very confused

Joreyk ( IXLLEGACYIXL )•16mo ago

variables have scopes where they live and a strict order how C# searches for variables for example you have

public void Bob()
{
  int x = 10;
}

public void Bob()
{
  int x = 10;
}

Then x is a local variable, it only exists in the scope of the bob method you cant touch it from outside of the method if you have

public class Mister
{
  int x = 11;

}

public class Mister
{
  int x = 11;

}

then x is a instance property ( i think that naming is incorrect ) when we combine now mister bob

public class Mister
{
  int x = 11;
public void Bob()
{
  int x = 10;
Console.WriteLine(x);
}
}

public class Mister
{
  int x = 11;
public void Bob()
{
  int x = 10;
Console.WriteLine(x);
}
}

then what will it print? C# ( and pretty much any other OOP language ) searches as locally as possible which means first it searches "do i have a local variable somewhere .. oh yes i have.. it has value 10" so this will print 10

public class Mister
{
  int x = 11;
public void Bob()
{
Console.WriteLine(x);
}
}

public class Mister
{
  int x = 11;
public void Bob()
{
Console.WriteLine(x);
}
}

now .. "do i have a local variable.. no i dont.. do i have a instance variable? ( as its the scope above ) oh yes i have it has value 11" but if you explicitly tell C# WHERE to search then it will take it from there

public class Mister
{
  int x = 11;
public void Bob()
{
  int x = 10;
Console.WriteLine(this.x);
}
}

public class Mister
{
  int x = 11;
public void Bob()
{
  int x = 10;
Console.WriteLine(this.x);
}
}

"you want the isntance variable of x.. it has 11 in it.. got you homie" the brackets pretty much define the scope of variables not entirely but for that you can remember that

McMahoneOP•16mo ago

Ahhh so much easier now. Thank you So the instance variable of x would be 11, since we explicitly write this.x?

Joreyk ( IXLLEGACYIXL )•16mo ago

if you have inheritance then you have also the "base" scope so you tell C# "look in the class where im inheriting from and search there the variable" yes, i had a typo

blinkbat•16mo ago

is the property you're affecting named exactly as the param? casing and all

Joreyk ( IXLLEGACYIXL )•16mo ago

yes thats what is about

blinkbat•16mo ago

yes exactly if you use capitalized properties you won't have this issue

Joreyk ( IXLLEGACYIXL )•16mo ago

how shadowing works thats another thing...this became over the years "less" important.. or atleast the cases you needed it went down as C# has fancy syntax features to avoid it as its confusing

blinkbat•16mo ago

yes I avoid using this where I can

Joreyk ( IXLLEGACYIXL )•16mo ago

but its good to know as you will meet other shadowing problems in future

Accord•16mo ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ initiating Constructor