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NaCl
Asked: 2020-04-20 05:56:48 +0800 CST 2020-04-20 05:56:48 +0800 CST

Directly access the overridden member?

  • 772

Good! I have 3 classes, one is TokenBase, which is used as parent of the other classes:

abstract class TokenBase
{
    public TokenTypes Type { get; set; }
    public virtual object Value { get; set; }
    public override string ToString()
    {
        return $"Type: {Type}\t\t Value: {Value}";
    }
}

Derived classes:

class StringToken : TokenBase
{
    private string _Value;
    public new string Value 
    {
        get { return _Value; }
        set { _Value = value;}
    }
    public StringToken(string v) { Type = TokenTypes.String; Value = v; }
}

class SymbolToken : TokenBase
{
    private string _Value;
    public new Symbols Value 
    {
        get { return _Value; }
        set { _Value = value;}
    }
    public SymbolToken(Symbols v) { Type = TokenTypes.Symbol; Value = v; }
}

The problem lies when I want to call ToString()o Valueon one of the derived classes inside the list:

public static void Main(string[] args)
{
    IList<TokenBase> Tokens = new List<TokenBase>();
    Tokens.Add(new StringToken("Hola Mundo"));
    foreach (TokenBase T in Tokens)
    {
        Console.WriteLine(T.ToString()); 
        // Obtengo la siguiente salida: "Type: String         Value: "
        Console.WriteLine(T.Value.ToString()); // Obtengo: ""
    }
    Console.ReadLine();
}

// Salida esperada: "Type: String         Value: Hola Mundo"

How can I directly access the property Valueof one of the derived types?

c#

2 Answers

  1. Best Answer

    But you do not need to do what you propose, by defining the property as virtual it has an implementation for the child classes that you could override, but in this case it is not necessary

    if you define

    abstract class TokenBase
{
    public TokenBase(TokenTypes type, string v)
    {
        Type = type; 
        Value = v; 
    }

    public TokenTypes Type { get; set; }
    public virtual object Value { get; set; }
    public override string ToString()
    {
        return $"Type: {Type}\t\t Value: {Value}";
    }
}



class StringToken : TokenBase
{
    public StringToken(string v) 
        : base(TokenTypes.String, v) 
    { 

    }
}

class SymbolToken : TokenBase
{
    public SymbolToken(string v) 
        : base(TokenTypes.Symbol, v) 
    { 

    }
}

    you can from the child classes assign the properties of the base

    Also if you define a property as virtual you are supposed to use the override

    If the behavior must change then you would do the following

    abstract class TokenBase
{
    public TokenBase(TokenTypes type)
    {
        Type = type; 
    }

    public TokenTypes Type { get; set; }
    public virtual object Value { get; set; }
    public override string ToString()
    {
        return $"Type: {Type}\t\t Value: {Value}";
    }
}



class StringToken : TokenBase
{
    public StringToken(string v) 
        : base(TokenTypes.String) 
    { 
        this.Value = v;
    }

    public override object Value 
    { 
        get{}; 
        set{ //aqui redefines la implementacion}; 
    }
}

class SymbolToken : TokenBase
{
    public SymbolToken(string v) 
        : base(TokenTypes.Symbol) 
    { 
        this.Value = v;
    }

    public override object Value 
    { 
        get{}; 
        set{ //aqui redefines la implementacion}; 
    }

}
    • 2

  2. If you change your class StringTokento the following, your example should work:

    class StringToken : TokenBase
{  
    public override object Value
    {
        get
        {
            return base.Value;
        }

        set
        {
            base.Value = value;
        }
    }

    public StringToken(string v) { Type = TokenTypes.String; Value = v; }
}

    Or if you want to keep your property Valueof type String, you can do something like this:

    class StringToken : TokenBase
{
    public new string Value
    {
        get { return base.Value.ToString(); }
        set { base.Value = value; }
    }

    public StringToken(string v) { Type = TokenTypes.String; Value = v; }
}
    • 0