How to use a Class variable in a Method

Questions & Answers
1

Hi, I have created a class(Aircraft) that I’m using as a data holder (That stores strings, ints, and enums) and have made a List(Aircraft) of that class. I would like to write a method that returns a new list from List(Aircraft) with the specific variables from Aircraft and its values.

public class AircraftManger : MonoBehaviour
{
    public List<Aircraft> aircraftsList = new List<Aircraft>();

    public void AddAircraft(string aircraftName, int numberOfWheels, int numberOfWings, 
    Aircraft.EngineType engineType)
    {
        aircraftsList.Add(new Aircraft(aircraftName, numberOfWheels, numberOfWings, engineType));
        aircraftsList.Sort((a1, a2) => a1.aircraftName.CompareTo(a2.aircraftName));
    }
    public void RemoveAircraft(string name)
    {
        foreach (Aircraft a in aircraftsList)
        {
            if (a.aircraftName == name) aircraftsList.Remove(a);
        }
    }
    **public List<Aircraft> ReturnAircraftsWithName(string name) //Returns a list of <Aircraft> with nam 
    e.
    {
        List<Aircraft> returnList = new List<Aircraft>();

        foreach (Aircraft a in aircraftsList)
        {
            if (a.aircraftName == name) returnList.Add(a);
        }

        return returnList;
    }
    public List<Aircraft> ReturnAircraftsWithNumberOfWheels(int numberOfWheels) //Returns a list of 
    <Aircraft> with number of wheels.
    {
        List<Aircraft> returnList = new List<Aircraft>();

        foreach (Aircraft a in aircraftsList)
        {
            if (a.numberOfWheels == numberOfWheels) returnList.Add(a);
        }

        return returnList;
    }**
}

public class Aircraft //Data Holder class
{
    public string aircraftName;
    public int numberOfWheels;
    public int numberOfWings;
    public enum EngineType {Piston, Turbine, Electrical}
    public EngineType engineType;

    public Aircraft(string aircraftName, int numberOfWheels, int numberOfWings, EngineType 
    engineType)
    {
        this.aircraftName = aircraftName;
        this.numberOfWheels = numberOfWheels;
        this.numberOfWings = numberOfWings;
        this.engineType = engineType;
    }
}

Now, instead of having to continue with the pattern of creating similar methods like ReturnAircraftsWithName, ReturnAircraftWithNumberOfWings, ReturnAircraftWithNumberOfWheels (Creating the same method for each variable in the Aircraft class) I would like to have a shorthand version of this. Something like:

    public List<Aircraft> ReturnAircraftsWithProperty(VariableName value) 
    {
        List<Aircraft> returnList = new List<Aircraft>();

        foreach (Aircraft a in aircraftsList)
        {
            if (a.Variablename == value) returnList.Add(a);
        }

        return returnList;
    }

So that I use a method like this to return a list Aircraft -

List<Aircraft> biplanes = ReturnAircraftsWithProperty(Aircraft.numberOfWings(2));

My actual code has an Aircraft class with over 20 variables so I don’t want to write 20 methods that are basically the same.

2

This is a great use case for LINQ. A set of extensions for collection types that allows easy manipulation and querying of collection data.

For example, if you want to have a list of all aircrafts with 2 wings, then:

using System.Linq;

List<Aircraft> aircraftsWithTwoWings = aircraftsList.Where(aircraft => aircraft.numberOfWings == 2).ToList();

That is all you have to do. And you can use the same pattern to produce lists of any kind of query.

3

LINQ is probably the easiest solution for this but would not be my favorite tbh. In general i still want to advise to not use LINQ where possible as it often has a heavy performance impact compared to basic for loop solutions.

I imagine that it might also be possible to create some function to the tune of:

public List<Airplane> getPlanesWithCondition(System.Func<Airplane, bool> comparefunc)
{
    foreach(var airplane in allAirPlanes){
         if(comparefunc.Invoke(airplane))
            //add...
    }
}

//in some code:
var conditionalList = getPlanesWithCondition((Airplane plane) => {return plane.winCount==2});

which has a similar notation and should work without linq.
Not sure if that really is faster/better though. Also not testet and somewhat pseudocode.