Can you use a string variable to determine which function to call? Or is there a better approach to editing variables within a class?

Question

I'm trying to create a function that takes two player classes, compares which AttackElement they used, and is able to alter each class' variables based on which AttackElement has a better advantage.

I'm sure there's a much more logical way of doing this, but at the moment I'm stuck wondering if I could concatenate a string to call the correct variable. For example, if I am trying to access a variable in a player class called WaterStrength can I simply have a string that combines the word "Water" with "Strength" in order to call the variable? I know calling functions/variables doesn't normally work that way, but in this example I'm calling this iWantToCombineThis.

int baseDamage = 2;

class PlayerClass(){
      int Health = 10;
      int WaterStrength = 1;
      int FireStrength = 1;
}

void AnalyzeRound(PlayerClass won, PlayerClass lost, string winningElement)
        {
            string iWantToCombineThis = winningElement + "Strength";
            lost.Health -= baseDamage * won.iWantToCombineThis;
        }

AnalyzeRound(Player1,Player2,"Water");
AnalyzeRound(Player2,Player1,"Fire");

Possible duplicate of [Calling a function from a string in C#](https://stackoverflow.com/questions/540066/calling-a-function-from-a-string-in-c-sharp) — Zze, Jul 08 '19 at 01:13
A `Dictionary` could be used to do this in a more appropriate way. — Bradley Uffner, Jul 08 '19 at 01:13
You can use reflection to get the field by its name, or you can create an enum for the elements and use switch case or if statements to check for the element — Sohaib Jundi, Jul 08 '19 at 01:18
@Zze - It's not a duplicate. There are other ways to do this without resorting to reflection. — Enigmativity, Jul 08 '19 at 01:19
A `Dictionary` would be most appropriate, or even better maybe make the strength type an enum and stop using strings all together. — Ian Mercer, Jul 08 '19 at 01:23

score 3 · Answer 1 · answered Jul 08 '19 at 01:23

You could use a Dictionary<string, Func<PlayerClass, int>> to get the value without resorting to reflection. Try this:

int baseDamage = 2;

class PlayerClass
{
    public int Health = 10;
    public int WaterStrength = 1;
    public int FireStrength = 1;
}

private Dictionary<string, Func<PlayerClass, int>> indirect = new Dictionary<string, Func<PlayerClass, int>>()
{
    { "WaterStrength", pc => pc.WaterStrength },
    { "FireStrength", pc => pc.FireStrength },
};

void AnalyzeRound(PlayerClass won, PlayerClass lost, string winningElement)
{
    int strength = indirect[winningElement + "Strength"](won);
    lost.Health -= baseDamage * strength;
}

score 3 · Accepted Answer · edited Jul 08 '19 at 01:39

3

A better approach would be to make the strength type an enum:

public enum StrengthType
{
    Water=1,
    Fire=2
}

And then have a method on the player class to get the Strength value for a given type from a dictionary mapping strength types to int values:

private Dictionary<StrengthType, int> strengthTypes = new Dictionary<StrengthType, int> 
{
   [StrengthType.Water] = 12,
   [StrengthType.Fire] = 15
};

public int GetStrength(StrengthType strengthType)
{
   return strengthTypes[strengthType];
}

edited Jul 08 '19 at 01:39

ProgrammingLlama

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answered Jul 08 '19 at 01:29

Ian Mercer

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+1 to using enums and a dictionary lookup. You could also use a switch/if statement on enums to select different functions or box/unbox objects. – Slipoch Jul 08 '19 at 03:12
Thank you all, I was actually using enums before but decided to simplify it for the purpose of this question. I hadn't considered using a Dictionary and that really seems like the best approach. I'm learning on my own and still so new to it all that I don't know what all is possible or best practices. – TheFlyingElbow Jul 08 '19 at 05:09

score 1 · Answer 3 · answered Jul 08 '19 at 01:22

Disclaimer: As the comments have noted, this is kind of an anti pattern and consider doing it statically.

But to answer your question, you could use reflection to do this:

public static class Utility
{
    static T GetDynamicValue<T>(this Object obj, string propertyName)
    {
        var flags = BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic;
        var prop = obj.GetType().GetProperty(propertyName, flags);
        var val =prop.GetValue(obj);
        return (T)val;
    }
}

And then you can say:

var x = won.GetDynamicValue<int>("iWantToCombineThis");
lost.Health -= baseDamage * x;

Can you use a string variable to determine which function to call? Or is there a better approach to editing variables within a class?

3 Answers3