I would like to know if it is possible to update or refresh (or something like that) a variable, without assigning new values. For example. I declare a vector and give it values, then declare a variable. N contains a formula. vector [0] = 2; vector [1] = 10; N = vector [i] * 10; At a certain moment I want that i = 1; Fx = N; and I want the value that N has to be updated before being stored.
There is no such thing as what you ask for, but you can have properties that return the computed value.
Option 1
It occurs to me that you can have a generic class that receives a function as a formula:
public class Formula<TResult>
{
public Formula(Func<TResult> formula)
{
Value = formula;
}
// cada vez que invoques a la propiedad Value, se ejecuta la función
// que pasaste por parámetro a la clase
public TResult Value { get; }
}
And to use it:
int value = 5; // el valor original
// en este caso, el '<int>' en el constructor le dice de que tipo es el valor que regresa la fórmula
var N = new Formula<int>(() => value * 10);
var result1 = N.Value; // result1 = 50
value = 10;
var result2 = N.Value; // result2 = 100
If you want to avoid putting the data type of the result of the formula, that is, removing the "" in "new Formula ", you can create a static class with a factory type method :
public static class Formula
{
public static Formula<TResult> From<TResult>(Func<TResult> formula)
{
return new Formula<TResult>(formula);
}
}
And so you do not have to write the data type of the result of the formula since the compiler will infer it:
int value = 5;
var N = Formula.From(() => value * 10);
var result1 = N.Value; // result1 = 50
value = 10;
var result2 = N.Value; // result2 = 100
If your formula is more complex, you have two options:
var N = Formula.From(() => {
int result;
// aquí irían todas las líneas de código
// para calcular el resultado
return result;
});
ó:
var N = Formula.From(Metodo);
.
.
.
.
private int Metodo()
{
int result;
// aquí irían todas las líneas de código
// para calcular el resultado
return result;
}
Option 2
If you want vectors, you can have a class that receives a vector and a formula, example;
public class Formula<T, TResult>
{
readonly T[] vector;
readonly Func<T, TResult> formula;
public Formula(T[] vector, Func<T, TResult> formula)
{
this.vector = vector;
this.formula = formula;
}
public TResult this[int index] => formula(vector[index]);
}
And to use it:
var vector = new[] { 2, 10 };
var N = new Formula<int, int>(vector, i => i * 10);
var value1 = N[0]; // value1 = 20
var value2 = N[1]; // value2 = 100
vector[0] = 4;
vector[1] = 20;
var value3 = N[0]; // value3 = 10
var value4 = N[1]; // value4 = 200
And as in the first class, you can create a static class with a static factory type method, I'm going to reuse the previous one:
public static class Formula
{
// método tipo factory ya creado anteriormente
public static Formula<TResult> From<TResult>(Func<TResult> formula)
{
return new Formula<TResult>(formula);
}
// método factory para la clase Formula de vectores:
public static Formula<T, TResult> From<T, TResult>(T[] vector, Func<T, TResult> formula)
{
return new Formula<T, TResult>(vector, formula);
}
}
Finally, with those classes, the value that returns the "formula" does not necessarily have to be the same type as the value of the original data, an example:
int meses = 1;
var N = Formula.From(() => DateTime.Today.AddMonths(meses));
var mesSiguiente = N.Value; // mesSiguiente = la fecha un mes adelante
meses = 5;
var enCincoMeses = N.Value; // enCincoMeses = la fecha 5 meses adelante