如何获取存储在数组中的类中的值？

Question

I'm making a C# script in Unity. My intention is to create a class Scenario , create classes representing different scenarios, which would then be stored in an array scenarioListAll .

A (simplified) version of the code is as follows:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class OverallManager2 : MonoBehaviour
{

public static object[] scenarioListAll = new object[40];

public class Scenario
{
    public string scenarioDesc;
    public bool surprise;     // The 'surprise' bool I want to reference is defined here
    public string surpriseType;
    public int[] leftOption;
    public int[] rightOption;
    public int scenarioNumber;

    public Scenario(string st, bool sp, int[] l, int[] r, int n)
    {
        scenarioDesc = st;
        surprise = sp;
        leftOption = l;
        rightOption = r;
        scenarioNumber = n;
    }

    // I haven't used this, but I'm not sure if this matters so I'm including this too
    public Scenario(string st, bool sp, string spt, int[] l, int[] r, int n)
    {
        scenarioDesc = st;
        surprise = sp;
        surpriseType = spt;
        leftOption = l;
        rightOption = r;
        scenarioNumber = n;
    }
}


public static int[] getArray(int a, int b, int c, int d, int e, int f)
{
    int[] arr = new int[6] {a, b, c, d, e, f};
    return arr;
}


// Storing scenarios, am looking for the bool (2nd position)
public Scenario s1 = new Scenario("Test1", false, getArray(1, 1, 1, 1, 1, 1), getArray(1, 1, 1, 1, 1, 1), 1);
public Scenario s2 = new Scenario("Test2", true, getArray(1, 1, 1, 1, 1, 1), getArray(1, 1, 1, 1, 1, 1), 2);
public Scenario s3 = new Scenario("Test3", false, getArray(1, 1, 1, 1, 1, 1), getArray(1, 1, 1, 1, 1, 1), 3);

    void Awake()
    {
        // Store scenarios in object array
        scenarioListAll[0] = s1;
        scenarioListAll[1] = s2;
        scenarioListAll[2] = s3;

        for(int i = 0; i < 40; i++)
        {
            object temp = scenarioListAll[i];     // Trying to extract the object stored in the array in a temp object
            bool surpriseCheck = temp.surprise;     // I am having problems with this line
            if(surpriseCheck == true)
            {
                // Do something
            }
        }
    }
// Ignoring start and update since they're irrelevant in this context
}

What I would like to do is to check whether the surprise element within a newly defined scenario (eg s1 ) is true. To do that, I was planning to extract the scenario stored in the array scenarioListAll , and then extract the surprise component from there. However, I'm couldn't figure out how to do this (eg in the code shown above, it returns Compiler Error CS1061).

I don't think I was able to find any documentation on this either, but I might not have understood something. I'm learning on my own so please bear with my poor knowledge/presentation.

Thank you for your time. Your help is much appreciated.

Answer 1

You are having a compilation issue due to the fact that the c# compiler doesn't know that temp is a Scenario since you declared it as "object". If you want to loop through the scenarios and check to see if they are a surprise you can use something like this:

 foreach(Scenario temp in scenarioListAll)
 {
        bool surpriseCheck = temp.surprise;     
        if(surpriseCheck == true)
        {
            // Do something
        }
 }

Another way of accomplishing the same task with more control over the iteration would be:

 for(int i = 0; i < scenarioListAll.Length; i++)
 {
        Scenario temp = scenarioListAll[i];
        bool surpriseCheck = temp.surprise;     
        if(surpriseCheck == true)
        {
            // Do something
        }
 }

The benefit of the first version is that you don't have to worry about overrunning the bounds of the array. As Mike added below you could also use var to have the compiler fill in the type for you.

Answer 2

It's sometimes easiest to allow the compiler to determine the type of a variable for us.

In your case, you've specified that the variable temp will be of type object . Now, that's fine, but while a Scenario derives from object , and object is the lowest level class in the .Net environment, and is not a Scenario .

The var keyword doesn't mean that the declared type is of a "variable" type, instead it's telling the compiler just to "fill in" the correct type, based on the action you're taking. So, to put this in to action in your case, you could do this instead:

    for( var i = 0; i < 40; i++ )                   // notice the use of var here as well
    {
        var scenario = scenarioListAll[i];          // renamed temp to scenario
        // var surpriseCheck = scenario .surprise;  // var used but line not required
        if( scenario.surprise )
        {
            // Do something
        }
    }

I went overboard there to demonstrate that the compiler is quite happy with the var keyword just about wherever you'd specify a data type as a type for a variable. Obviously not when you're trying to cast types, and there ARE sometimes where you'd want to specify the exact type you're trying to instantiate.

In your case, your next issue will be that you've defined the array as having 40 object elements, but you've then only instantiated 3 Scenario elements (which is valid, but probably not quite what you want overall). So your code, as it stands, is going to NullReference error out. You'll be able to avoid that, with a small modification, so your amended code could look like this, to include some type checks:

for( var i = 0; i < scenarioListAll.Length; i++ )
{
    // First, check to see if the object in the array cell is a Scenario.
    // If the item in the cell is a Scenario, check to see if surprise is set.
    if ( scenarioListAll[i] is Scenario scenario && scenario.surprise )
    {
        // Do something
    }
}

for more information on the is keyword, check the Microsoft Docs here .