CODEWITHSUNDEEP
c#
dez82
dez82

Reputation: 77

Getting a really strange logic error which I don't understand

This code is supposed to output lines which say

trex (2 legged) dinosaur (extinct)

For a list of animals taken from a file. If the animal isn't extinct, it is skipped by the if statement.

Everything works fine, except for the last bit, which should say (extinct).

Instead it said "true" or "false" depending on how I set up the isExtinct property.

Now I've put an if statement into the isExtinct property to output "extinct" but I get an error post compilation

Stacktrace:


Native stacktrace:

mono() [0x8105b4a]
mono() [0x8153274]
mono() [0x806a20b]
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Debug info from gdb:


=================================================================
Got a SIGSEGV while executing native code. This usually indicates
a fatal error in the mono runtime or one of the native libraries 
used by your application.
=================================================================

Aborted (core dumped)

Code below

class MainClass
{
    public static void Main (string[] args)
    {

        StreamReader input = new StreamReader ("animals.txt");

        while (!input.EndOfStream) {    
            string line = input.ReadLine ();
            string[] data = line.Split (',');
            if (data [3] == "true") {
                Animal myAnimal = new Animal (data[0], Convert.ToInt32(data[1]), data[2], Convert.ToBoolean(data[3]));
                Console.WriteLine (myAnimal);
                }
        }
    }
}
}

public class Animal
{
    string species;
    int legs;
    string genus;
    bool extinct;

    public Animal (string species, int legs, string genus, bool extinct)
    {
        this.species = species;
        this.legs = legs;
        this.genus = genus;
        this.extinct = extinct;
    }

    public string Species{ get; set;}
    public int Legs{ get; set;}
    public string Genus{ get; set;}
    public string isExtinct{ 
        get
        {
            return isExtinct;
        }
        set 
        {
            if (extinct == true) {
                isExtinct = "extinct";
            } else {
                isExtinct = "";
            }
        }
    }

    public override string ToString(){
        return String.Format("{0} ({1} legged) {2} ({3})", species, legs, genus, isExtinct);
    }
}
}

Upvotes: 0

Views: 60

Answers (2)

musefan
musefan

Reputation: 48425

Quick Fix

Well that isExtinct property looks like a problem... try this one:

public string isExtinct
{
    get { return extinct ? "extinct" : "" }
}

That should fix it, but I would say you probably want to consider a cleanup...

Clean Up

For example, I would argue not having the getter at all. Just do the logic in your ToString method (as that is likely the only place that will need to use it anyway), then you can make the brackets conditional too. Something like:

public override string ToString()
{
    string result = String.Format("{0} ({1} legged) {2}", species, legs, genus);
    if(extinct)
        result += " (extinct)";

    return result;
}

Suggested Code

In addition, your properties Species, Legs, and Genus don't have any use, they are not tied to your fields anyway. I would suggest removing the fields and stick with just the 4 properties:

public string Species{ get; set;}
public int Legs{ get; set;}
public string Genus{ get; set;}
public string IsExtinct { get; set;}

public Animal (string species, int legs, string genus, bool isExtinct)
{
    Species = species;
    Legs = legs;
    Genus = genus;
    IsExtinct = isExtinct;
}

public override string ToString()
{
    string result = String.Format("{0} ({1} legged) {2}", Species, Legs, Genus);
    if(IsExtinct )
        result += " (extinct)";

    return result;
}

Upvotes: 2

Ben Jackson
Ben Jackson

Reputation: 1138

Your property logic was wrong - you don't want two separate writable properties and your syntax incorrect.

Try this :

public string isExtinct { 
        get
        {
            if (extinct == true) {
                return "extinct";
            } else {
                return "";
            }        
        }
}

Upvotes: 1

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