将用户输入的字符串转换为c＃中的对象

Question

I have a battleship like terminal game, the user enters a coordinate like e2, and the program checks one of the instance variables of my object Box, it checks whether hasShip is true, if its true then it will make the coordinate e2 false, and give the output "Ship destroyed"

The problem is that all my objects are called a1,a2,a3,a4,a5,b1,b2 and so on.

I have created 25 instances of the Box class. All names as such.

Once the program gets input, either e4 ,e5 etc. I want to convert that string into an object.

For example( I want to do something like this )

target = Console.ReadLine();
target.hasShip == true; 

I want to convert target into an object, then use target to use the methods of the Box class.

Because the other approach requires me to make loads of if statements, which isn't clean code, doesn't look good, and is a waste if you ask me.

Thanks in advance,

Answer 1

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New Answer: use an Array

I am slow. I did not pay attention that you are making a battleship-like game, and that we know that the "boxes" make a rectangle. We can store this efficiently in an array.

Why I did not catch up to this fact earlier? I guess I need to wake up properly.

So, use an array:

var board = new Box[5, 5];

Now, to populate it, we can do a double for loop:

for(var indexRow = 0; indexRow < 5; indexRow++)
{
    for(var indexCol = 0; indexCol < 5; indexCol++)
    {
        board[indexRow, indexCol] = new Box();
    }
}

Note : pay attention that the indexes go from 0 to 4. For a total of 5 values: {0, 1, 2, 3, 5}.

And to query from it, we will need the indexes...

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Addendum on populating the array

In comments, OP has said that each Box has an id and the ship positions are picked at random.

We can give the id in the loop:

for(var indexRow = 0; indexRow < 5; indexRow++)
{
    for(var indexCol = 0; indexCol < 5; indexCol++)
    {
        var box = new Box();
        box.vhID = (((char)(((int)'a') + indexRow))).ToString() + ((char)(((int)'1') + indexCol)).ToString();
        board[indexRow, indexCol] = box;

    }
}

What I am doing here is constructing the id from the indexes. Basically taking the value of 'a' and adding the indexRow will give us 'a' when indexRow is 0 , 'b' when it is 1 and so on. Similarly, we get the digit that represents the column.

Note : We convert the char to int , do the addition, then convert back to char ... and then from char to string . Once we have string, we can concatenate them.

I do not think we need this id. But, hey, you can do it like this.

OP also mentions that he will pick 4 ship positions at random. Fair enough:

var random = new Random();
for (var ships = 0; ships < 4; ships++)
{
    board[random.Next(0, 4), random.Next(0, 4)].hasShip = true;
}

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Since the user inputs an string, I suggest to create a function to convert it to the index pair:

 var input = Console.ReadLine();
 if (TryGetCoordinates(input, out int irow, out int icol))
 {
     var target = board[irow, icol];
 }
 else
 {
     Console.WriteLine("The cell {0} does not exist.", input);
 }

 // ...

 bool TryGetCoordinates(string cell, out int indexRow, out int indexCol)
 {
     // ...
 }

Start by validating null :

 bool TryGetCoordinates(string cell, out int indexRow, out int indexCol)
 {
     indexRow = -1;
     indexCol = -1;
     if (cell == null)
     {
         return false;
     } 
     // ...
 }

Note : Feel free to use Trim , ToUpper or ToUpperInvariant .

We know that must be a letter followed by a digit, we can validate the length:

 bool TryGetCoordinates(string cell, out int indexRow, out int indexCol)
 {
     indexRow = -1;
     indexCol = -1;
     if (cell == null)
     {
         return false;
     }
     if (cell.Length != 2)
     {
         return false;
     }
     // ...
 }

We extract the characters and from them the coordinates. Noting that the first one is a letter, and the other a digit. We can also validate they are withing bounds.

 bool TryGetCoordinates(string cell, out int indexRow, out int indexCol)
 {
     indexRow = -1;
     indexCol = -1;
     if (cell == null)
     {
         return false;
     }
     if (cell.Length != 2)
     {
         return false;
     }
     indexRow = (int)cell[0] - (int)'a';
     indexCol = (int)cell[1] - (int)'1';
     return indexRow < 5 && indexRow >= 0 && indexCol < 5 && indexCol >= 0;
 }

And of course, you can do a loop of the validation similar to what was explained in the old answer.

Note : the issue with value types I describe in the old answer still applies with the array.

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Old Answer: Use a Dictionary

I believe you do not want to convert the string to an object (the string is an object by the way), you want to pick the Box object you previously created based on the string . And you want to do it without using if statements. What you need is a dictionary.

So, you would have Dictionary<string, Box> meaning that it is a dictionary that you can query by string and stores Box .

Addendums :

• In this case, string is the key type, by which we will access the dictionary. When we add an object to the dictionary we identify it with a key, and when we retrieve it, we also use the key. The key does not have to be string , you can choose a different type. string is convenient in this case because it is what you get from Console.ReadLine() .
• You can create the dictionary to store whatever type you need. If you do not need Box , you can create a dictionary that stores something else.

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Creating and populating the Dictionary

Then, you add to the Dictionary all your Box objects, like this:

var dict = new Dictionary<string, Box>();

// ...

dict.Add("a1", CreateBoxA1());

Where CreateBoxA1 represents whatever means you have to create the object. No, you do not need to create a method for each Box ... you can do it like this:

dict.Add("a1", new Box());

Or whatever. I do not know how you create them, so consider that a placeholder, ok? ok.

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Querying and retrieving values from the Dictionary

Once you have all your Box instances in your dictionary, you can get the one you need using the string :

Console.WriteLine("Enter the name of the Box:");
var name = Console.ReadLine();
var target = dict[name];

Addendum : The value you get from dict[name] is the value that you added to the dictionary with that key. So, if the user typed "a1" it dict[name] will be the value that we added with "a1" ( dict.Add("a1", new Box()); ). Again, if what you need is not Box you can create a dictionary to store a different type.

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Input validation

You can also use the Dictionary to validate if the string corresponds to a Box that exists, for example:

Console.WriteLine("Enter the name of the Box:");
var name = Console.ReadLine();
if (dict.KeyExists(name))
{
    var target = dict[name];
    // ...
}
else
{
    Console.WriteLine("The Box {0} does not exist", name);
}

It goes without saying, but... you can make a loop based on that, for example:

Box target = null;
while(true)
{
    Console.WriteLine("Enter the name of the Box:");
    var name = Console.ReadLine();
    if (dict.KeyExists(name))
    {
        target = dict[name];
        break;
    }
    Console.WriteLine("The Box {0} does not exist", name);
}

Also, it goes without saying, but... you can add your own validations and sanitation steps. For example using ToUpper , ToUpperInvariant or Trim . And I would remind you that changing string s to lower or upper case is culture sensitive.

See also: Best Practices for Using Strings in .NET .

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Editing an removing objects from the dictionary

Once you have the object you retrieved from the Dictionary...

 var target = dict[name];

We can use it, and even modify it:

 var target = dict[name];
 if (target.hasShip) // no need for "== true" if hasShip bool
 {
      target.hasShip = false;
      Console.WriteLine("Ship Destroyed");
 }

An special note must be done if Box is value type. For a custom type that means that it is not a class but a struct . The problem with value types is that they are copied on assignment, meaning that when you do var target = dict[name]; with a value type, you get a copy. You must then update the dictionary once you manipulated it:

 var target = dict[name];
 if (target.hasShip) // no need for "== true" if hasShip bool
 {
      target.hasShip = false;
      dict[name] = target;
      Console.WriteLine("Ship Destroyed");
 }

Note : As I said above, this is only needed for value types.

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And you can even remove the Box from the dictionary if that is necesary:

dict.Remove(name);